DPS FUEL INJECTION PUMP - Auto Kelly · Não exponha a pele a jactos de combustível sob pressão,...

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PRINCIPLES OF OPERATION DPS FUEL INJECTION PUMP 2009 DDGX136A(EN)

Transcript of DPS FUEL INJECTION PUMP - Auto Kelly · Não exponha a pele a jactos de combustível sob pressão,...

Page 1: DPS FUEL INJECTION PUMP - Auto Kelly · Não exponha a pele a jactos de combustível sob pressão, especialmente os devidos a ... The DPS is a compact, distributor-type fuel injection

PRINCIPLES OF OPERATIONDPS FUEL INJECTION PUMP

2009DDGX136A(EN)

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Usare guanti adatti.Geeignete Schutzhandschuhe tragen.

Aangepaste veiligheidshandschoenendragen.Usen guantes adecuados.

Wear suitable gloves. Use luvas apropriadas.

Porter des gants appropriés.

Ver van open vuur en ontstekingsbronnenhouden - Niet reken.

Conservar alejado de toda llamao fuentede chispas - No fumar.

Conservare lontano da fiammee scintille - Non fumare.

Von Zündquellen fernhalten- Nicht rauchen.

Keep away from sources of ignition- No smoking.

Mantenha afastado de fontes de ignição - Proibido fumar.

Conserver à l'écart de toute flamme ousource d'étincelles - Ne pas fumer.

Proteggersi gli occhi/la faccia.Schutzbrille/Gesichtsschutz tragen.

Wear eye/face protection. Use protecção da face/olhos.

Veiligheidsbril/-masker gebruiken.Úsese protección para los ojos/la cara.

Porter un appareil de protectiondes yeux / du visage.

Kommen Sie nicht mit dem Hochdruckstrahl in Verbindung! Besonders nicht, wenn Druckrohrleitung oder Dichtung geprüft werden! Hochdruckflüssigkeiten können tödliche Verletzungen verursachen! Im Falle einer Berührung mit der Haut, kontaktieren Sie soforteinen Arzt. Bitte beachten Sie die Gesundheits-/und Sicherheitsunterlagen.

Ne pas approcher les mains ni le corps des jets de liquides, particulièrement ceux provenant des fuites de tuyaux et des joints soumis à la haute pression. Le liquide sous haute pression injecté sous la peau peut causer des blessures mortelles. En cas d’injection sous la peau, consulter immédiatement un médecin. Se reporter a la fiche de santé et de sécurité du gazole.

Do not put your skin into the fuel jets under pressure, especially those due to pressurepipe or seal leaks. High pressure liquids can cause deadly injuries. In case of an injectionunder the skin, contact a doctor immediately. Please refer to the health and security fuel documents.

Não exponha a pele a jactos de combustível sob pressão, especialmente os devidos afugas de tubos de pressão ou vedantes. Líquidos a alta pressão podem causar ferimentosmortais. No caso de injecção subcutânea, consulte imediatamente um médico. Consulte or favor a documentação respeitante a saúde e segurança de combustíveis.

Non esporre le mani o altre parti del corpo a getti di gasolio ad alta pressione, specialmente a quelli provenienti da tubi o paraolii. I getti di liquidi ad alta pressione possono causare ferite anche mortali. In caso di iniezione sotto pelle contattare immediatamente un medico. Fare riferimento alle schede di sicurezza del gasolio.

dheids-en veiligheidsfiche met betrekking tot de brandstof.z

Zorg dat uw handen of andere lichaamsdelen niet in contact komen met vloeistofstralenonder hoge druk, met name bij een lek aan een leiding of dichting. Als de vloeistof onder hoge druk onder de huid terechtkomt, kan dit zelfs tot dodelijke verwondingen leiden. Als de vloeistof onder de huid terechtkomt, onmiddellijk een arts raadplegen. Lees de gezon-

Mantenga las manos y el cuerpo lejos del rociado del líquido, especialmente inyectores, tuberías y juntas de alta presión con fugas. La inyección de alta presión puede perforar la piel humana y producir una lesión fatal. En caso de que la inyección atraviese la piel, consiga atención médica inmediatamente. Vea la hoja de Datos de Sanidad y Seguridad.

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INTRODUCTION I

WORKING PRINCIPLES II

TRANSFER PRESSURE CONTROL III

METERING, PUMPING AND DISTRIBUTION IV

GOVERNING V

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DDGX136A(EN) Principles of Operation Manual - DPS Fuel Injection Pump

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MAXIMUM FUEL DELIVERY CONTROL VI

ADVANCE CONTROL VII

OTHER FEATURES VIII

APPENDIX IX

Produced and published by:

Delphi Diesel Systems Ltd.Spartan CloseWarwick CV34 6AG Tel: +44 (0) 1926 472 900England Fax: +44 (0) 1926 472 901

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1. INTRODUCTION1.1 The Pump.......................................................................................................................................................................1-11.2 This Manual...................................................................................................................................................................1-3

INTRODUCTION I

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2. WORKING PRINCIPLES2.1 Principal Components...................................................................................................................................................2-52.2 Hydraulic Circuit............................................................................................................................................................2-8

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3. TRANSFER PRESSURE CONTROL3.1 Priming.........................................................................................................................................................................3-113.2 Transfer Pressure Generation....................................................................................................................................3-113.3 Transfer Pump Blades.................................................................................................................................................3-123.4 Transfer Pressure Regulation.....................................................................................................................................3-123.5 Transfer Pressure Relief Valve...................................................................................................................................3-13

TRANSFER PRESSURE CONTROL III

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4. METERING, PUMPING AND DISTRIBUTION4.1 Metering Of Fuel..........................................................................................................................................................4-154.2 Charging And Injection...............................................................................................................................................4-154.3 Hydraulic Head And Rotor Assembly........................................................................................................................4-164.4 Equalisation Groove....................................................................................................................................................4-164.5 High Pressure Outlets.................................................................................................................................................4-17

4.5.1 Delivery valves...........................................................................................................................................4-174.5.2 Pressurising valves....................................................................................................................................4-17

4.6 Axial Outlet Hydraulic Head.......................................................................................................................................4-18

IV METERING, PUMPING AND DISTRIBUTION

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5. GOVERNING5.1 Governor Components...............................................................................................................................................5-195.2 Two-Speed Governor..................................................................................................................................................5-195.3 All-Speed Governor....................................................................................................................................................5-195.4 Anti-Stall Device..........................................................................................................................................................5-20

GOVERNING V

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6. MAXIMUM FUEL DELIVERY CONTROL6.1 Scroll Plate Operation.................................................................................................................................................6-21

6.1.1 Excess fuel position...................................................................................................................................6-226.1.2 Maximum fuel position..............................................................................................................................6-22

6.2 Mechanical Excess Fuel..............................................................................................................................................6-236.3 Hydraulic Excess Fuel.................................................................................................................................................6-236.4 Torque Control............................................................................................................................................................6-256.5 Turbocharger Boost Control.......................................................................................................................................6-26

VI MAXIMUM FUEL DELIVERY CONTROL

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7. ADVANCE CONTROL7.1 Automatic Advance And Start Retard Device...........................................................................................................7-297.2 Manual Idling Advance Device...................................................................................................................................7-297.3 Head Locating Fitting (And Damper Assebly, When Fitted)....................................................................................7-307.4 Servo-Assisted Advance Device With Externally Controlled Light Load Advance................................................7-307.5 Cold Idle Advance (CIA) And Fast Idle.......................................................................................................................7-32

ADVANCE CONTROL VII

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8. OTHER FEATURES8.1 Pump Drive Shaft........................................................................................................................................................8-338.2 Latch Valve...................................................................................................................................................................8-338.3 Rotor Vent Switch Valve.............................................................................................................................................8-348.4 Cambox Pressurising Valve........................................................................................................................................8-368.5 Solenoid Shut-Off........................................................................................................................................................8-368.6 External Mechanical Stop...........................................................................................................................................8-378.7 "Flatted" Metering Valve.............................................................................................................................................8-38

VIII OTHER FEATURES

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9. APPENDIX9.1 Abbreviations Used In This Manual..........................................................................................................................9-41

APPENDIX IX

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IX APPENDIX

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1.1 The PumpThe DPS is a compact, distributor-type fuel injection pump designed primarily to meet the specialised requirements ofnaturally-aspirated and turbocharged diesel engines installed in light to medium duty, road-going vehicle, agricultural,tractor, industrial, and marine, applications.The pump is produced with either 2 or 4 pumping plungers and is suitable for 3-, 4-, and 6- cylinder engines of up to 1,6litres per cylinder. It can be specified for both Direct (DI) and Indirect (IDI) injection engines.The pump is flange-mounted to the engine. It is oil-tight and, during operation, all moving parts are lubricated by fueloil under pressure so that no additional lubrication system is required. Fuel pressure, which may be maintained withinthe pump housing by a spring-loaded valve assembly located on the governor control cover, prevents the ingress ofdust, water and other foreign matter.The pump has a solid, one-piece, drive shaft with no backlash between driving and driven members; this rigiditycontributes to consistency of performance, particularly at high pumping pressures. This one-piece design also allowsthe use of gear or belt drives.The pump has externally-adjustable maximum fuel control and may be specified with automatic excess fuel as an aidto engine starting. This control of the maximum fuel is of particular importance, as it allows the addition of other devices,such as torque control and turbocharger boost control, to meet differing engine requirements.Other special features, such as light-load advance and cold idling advance with fast idling control, may also beincorporated in the DPS to further improve pump performance.Some changes to the basic design have also been made to simplify installation, improve performance, and to facilitateease of manufacture. These changes are progressively introduced as new applications are developed and are,specifically:1. The existing radial outlet hydraulic head is to be replaced with a version in which the outlets are parallel to the axis

to the head.2. The rotor vent switch valve is deleted and its function of venting air from the low-pressure system is carried out

by a modified ("flatted") metering valve.The variety of features and design changes often results in pumps for different applications having radically differentexternal appearance, as illustrated by Fig. 1.

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Fig. 1 Three different DPS pumps

TopFour cylinder high speed direct injection (HSDI) pump with hydraulic excess fuel, solenoid stop, cold idle advance,fast idle, torque control, transfer pressure relief valve and servo-assisted advance with external control of light loadadvance.Middle rightFour cylinder axial outlet pump with hydraulic excess fuel and external mechanical stop.Bottom leftSix cylinder radial outlet pump with boost control, hydraulic excess fuel, solenoid stop and external mechanicalstop, advance damper and "flatted" metering valve (no rotor vent switch valve).

I INTRODUCTION

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1.2 This Manual

The DPS pump has many differing and complex features, the form and function of which are described in some detail.Whilst the illustrations may show particular pump types, they are only chosen to illustrate specific features or for generalcomparison.Section 2 (Working Principles) explains the overall functioning of the pump in both mechanical and hydraulic terms. Theremaining sections give more detailed explanations of the principles of the pump's operation, and contain sub-sectionson the principal features as necessary.

Fig. 2 Sectioned view of the HSDI DPS pump.

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I INTRODUCTION

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2.1 Principal ComponentsRefer to Fig. 3.The pump has a solid, one-piece. drive shaft (28). Rollers and shoes (21) are contained within the shaft and the torquerequired to generate the pumping force is imparted directly by the pump drive gear. Therefore, there are no backlashpoints between driving and driven members. This rigidity contributes to consistency of performance, particularly at highpumping pressures. The one-piece design also allows the front and rear bearings (27) and (22) to be located wide apart,minimising wear from side loads imposed by gear or belt drives.During operation of the pump, fuel supplied to the inlet connection (12) in the end plate passes to a vane-type transferpump (15), which raises the pressure of the fuel.The regulating valve in the end plate controls the level of transfer pressure presented to the metering valve (13), whichis operated, in conjunction with the mechanical governor, by the throttle lever (5). The metering valve regulates the flowof fuel to the inlet ports in the distributor rotor (19). The rotor carries one or two pairs of opposed high-pressure pumpingplungers (23) which, under the action of fuel at metering pressure. push the rollers apart. The extent of plungerdisplacement determines the amount of fuel injected into the engine cylinder. As rotation continues, the rollerssubsequently make contact with the internal lobes of the cam ring (9) and high-pressure pumping commences.Maximum delivery is pre-set by a sealed external adjuster (26) which controls the position of a sliding carriage calledthe "scroll link plate" (7). This, in turn, controls the positions of a pair of scroll plates (10) located either side of the camring. These act as check plates, limiting the outward movement of the rollers, and hence the plungers, and can be partiallyrotated to adjust the maximum delivery level.

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1 Governor main spring 17 High pressure outlet2 Fuel backleak connection 18 Pressurising or delivery valve3 Idling speed screw 19 Rotor4 Maximum speed screw 20 Advance device5 Throttle lever 21 Cam roller and shoe6 Link plate return spring 22 Rear bearing7 Scroll link plate 23 Pumping plungers8 Manual stop lever 24 Governor weight9 Cam ring 25 Governor weight retainer10 Scroll plates 26 Maximum fuel adjusting screw11 Stop solenoid 27 Front bearing12 Fuel inlet connection 28 Drive shaft13 Metering valve 29 Governor arm14 Fuel coarse filter 30 Governor link15 Transfer pump 31 Idling spring16 Transfer pressure regulating piston

Fig. 3 Cut-away view of a typical DPS pump.

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1 Latch valve 2 Rotor vent switch valve

Fig. 4 Three-quarter views of the DPS pump

The scroll plate mechanism can also be arranged to give automatic excess fuel delivery on starting. When the engine isshut down, the scroll plates are rotated to a point which allows the pumping plungers to move further apart to admitfuel in excess of the normal maximum the next time that the engine is started. This scroll plate position is maintainedduring cranking but as soon as the engine is self-sustaining (at a speed higher than cranking) provision of excess fuel isterminated by the action of the governor on the metering valve, reducing the fuel delivery level to that required at idling.The scroll link plate can be placed in the excess fuel position by either hydraulic or mechanical control, depending uponthe pump specification. Both methods give automatic excess fuel delivery on starting although the mechanical controlmethod additionally requires the throttle lever to be in the idling position. Section 6 (Maximum Fuel Delivery Control)describes the operation of both excess fuel control methods.As a further aid to starting, the advance unit can be specified to automatically adjust the cam ring (9) to retard injectiontiming. When, after cranking, the engine becomes self-sustaining, the advance device (20) turns the cam ring againstthe direction of pump rotation to advance the timing as engine speed increases. Some early pump specifications includeda lever which was operated manually to provide additional advance for use when the engine was cold to improvecombustion quality and avoid light load misfire until the engine attained its normal operating temperature.If fitted, a "latch-valve" ((1), Fig. 4) and a "rotor vent switch valve" ((2), Fig. 4) are located on either side of the pump andconnect with passages in the hydraulic head. In addition they act as hydraulic head fixings.The latch valve ensures that, at engine cranking speed, transfer pressure does not reach the auto-advance unit until theengine is self-sustaining, thus preventing premature advance of timing. In the case of pumps fitted with hydraulic controlof excess fuel, premature disengagement is avoided by isolating transfer pressure from the excess piston until the engineis self-sustaining.The rotor vent switch valve is provided to vent any air trapped between the pumping plungers through a vent orifice inthe hydraulic head. The valve provides the self-venting capability of the pump, avoiding the need to bleed the pumpafter initial installation or after the engine has been allowed to run out of fuel. When the engine is self-sustaining, transferpressure opens the latch valve, directing fuel to the advance device and to the rotor vent switch valve, thus closing thevent passage to the cambox.

Note:Later pump specifications do not have a rotor vent switch valve; air is vented from the rotor by a "flatted" metering valve(see section 8 (Other Features)).

The governor is of the mechanical flyweight type and is fitted with a "cush-drive" weight retainer (25), which isolates theweights (24) from the effects of torsional oscillation of the drive shaft. The number of weights used may be 3, 4, or 6,depending upon the pump application requirements.

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Depending upon whether a governor main spring (2) or a spring "pack" is installed, the governor may give "all-speed"or "two-speed" control. Section 5 (Governing) details both the governor components and these governor options.A solenoid-operated fuel shut-off valve (11) screwed into the upper part of the hydraulic head controls the fuel supplyto the metering valve. The solenoid valve provides "ignition key" shut-off.

2.2 Hydraulic Circuit

Refer to Fig. 5.

Note:A typical hydraulic circuit is illustrated. This depicts a basic DPS pump with a rotor vent switch valve, a differential latchvalve and an auto-advance device with a manual cold idling advance lever. The effect on the circuit of superseding therotor vent switch valve with a "flatted" metering valve is illustrated in section 8 (Other Features). The latter illustrationdepicts the most complex DPS pump, i.e. with hydraulic excess fuel, servo advance with light load advance, and torquecontrol.

Fuel is drawn from the fuel tank (2) through a sedimenter or water detector (4) and then passes through a main filter (8).Depending upon the relative levels and positions of the fuel tank, filter and injection pump, a separate engine-drivenfuel feed pump (9a) may be fitted. If no feed pump is fitted, a hand primer (9b) may be fitted; the purpose of this is toenable any free air trapped within the fuel circuit to be vented prior to starting the engine. Fuel, at feed pressure (E),passes into the transfer pump (11) which raises the pressure to a higher value termed "transfer pressure" (B), controlledby the regulating valve (10).In operation, the regulating valve maintains a pre-determined relationship between transfer pressure and the speed ofpump rotation by returning part of the fuel to the inlet side of the transfer pump.The transfer pump supplies fuel to the metering valve and, via a separate passage, actuates the latch valve (13).Fuel at transfer pressure (B) flows around an annular groove in the hydraulic head (12) adjacent to the transfer pump. Itthen passes via a solenoid shut-off valve (6) into a drilling in the top of the hydraulic head sleeve. Fuel then flows to themetering valve (5), which can be rotated by the governor control linkage (19), thereby regulating the flow of fuel to themetering ports.As fuel passes through the metering valve orifice in the hydraulic head, a pressure drop occurs, reducing transfer pressure(B) to a level known as "metering pressure" (C). Fuel from the metering valve then passes into two oblique meteringports via a circular groove in the sleeve to the rotor inlet ports, then through a central drilling in the rotor to one or twopairs of opposed pumping plungers. These are actuated by an internally-lobed cam ring.The lobes of the cam ring are "phased" with the drillings in the hydraulic head and rotor which allow alternate filling andinjection. The rotor ports first charge the pumping plungers at metering pressure (C), then fuel is pumped from thedistributor port at injection pressure (A) to each of the injectors (17) in turn.Cambox pressure (F) may be maintained by a spring-loaded pressurising valve (1) which unloads excess pressure in thecambox and returns the backleakage fuel (G) either to the filter or directly to the fuel tank. Backleakage from the injectorsis also returned either to the filter or to the fuel tank.To actuate the latch valve (13), fuel at transfer pressure (B) flows into a drilling in the bottom of the hydraulic head sleeveand, via an annular groove in the sleeve, to the latch valve.At cranking speeds, the latch valve is closed and prevents fuel at transfer pressure (B) flowing either to the advance unit(15), which therefore remains in the retarded position, or the rotor vent switch valve (18). The passages to the rotor ventswitch valve and advance unit remain at cambox pressure (F). The rotor vent switch valve is spring-loaded to the openposition, allowing fuel and air from the rotor to be vented via the cambox to the pressurising valve.At a pre-determined transfer pressure above that at cranking speed, the latch valve opens to allow fuel at pressure (B)to flow via an annular groove in the hydraulic head sleeve to the head locating fitting (16). From the head locating fitting,fuel flows to the underside of the stem of the rotor vent switch valve (18) lifting the valve and closing the rotor ventpassage to the cambox. Fuel also flows from the head locating fitting to the pressure side of the piston of the automaticadvance and start-retard unit (15).

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With further increase in pump speed, rising transfer pressure (B) acts upon the advance piston, rotating the cam ringand thus advancing injection timing. Leakage from the advance device flows back to the cambox.Two orifices, one in the latch valve and the other in the passage way between the latch valve and the cambox, are utilisedto generate an "intermediate" pressure (D). This pressure is generated only at cranking speed, when both orifices areopen.When the engine is self-sustaining, transfer pressure exceeds the combined effect of intermediate pressure and springforce; the latch valve opens, the valve orifice closes and intermediate pressure is reduced to cambox pressure.The latch valve as described above is of the 'differential' type and will close at a lower pump speed than that at which itopens i.e., only when transfer pressure drops below the combined effect of the latch valve spring force and camboxpressure. A non-differential latch valve is described in section 8 (Other features).

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A Injection pressure 9a Feed pump (when fitted)B Transfer pressure 9b Hand primer (when fitted)C Metering pressure 10 Regulating valveD Intermediate pressure 11 Transfer pumpE Feed pressure 12 Hydraulic head and rotorF Cambox pressure 13 Latch valveG Backleakage 14 Manual cold idling advance lever1 Pressurising valve 15 Automatic advance and start-retard unit2 Fuel tank 16 Head locating fitting3 Throttle shaft 17 Injector4 Sedimenter/water detector 18 Rotor vent switch valve5 Metering valve 19 Two-speed mechanical governor and control linkage assembly6 Shut-off solenoid 20 Cambox7 Vent orifice 21 Idle shaft8 Filter

Fig. 5 Diagrammatic layout of a typical DPS hydraulic circuit.

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3.1 PrimingRefer to Figs. 6 and 8.

When priming the pump from an external hand primer,with the engine stationary, fuel entering the end platecannot pass through the transfer pump and into the fuelpassages in the hydraulic head in the normal way. Fuelat priming pressure (or feed pressure (E) as indicated inFig. 8 (a)) enters the regulating sleeve (4) and acts on theupper face of the regulating piston (6). The piston isforced to the lower end of the sleeve, compressing thepriming spring (7) and uncovering the priming ports.Fuel then passes through the priming ports and the lowerfuel passage to the outlet side of the transfer pump andthen into the fuel passages within the hydraulic head.

3.2 Transfer Pressure Generation

Refer to Figs. 6 and 7.

The transfer pump comprises a rotor (11), eccentric liner(9) and sliding blades (10). The rotor is screwed into thedistributor rotor (12) and is tightened against the normaldirection of rotation of the injection pump to prevent thetransfer rotor being unscrewed when running.Fuel at feed pressure (E) enters the upper chamber of thepump formed by the pump blades, liner, and rotor andis displaced downwards as the rotor and blades turn. Itis ejected from the pump at transfer pressure (B). Theoutput of the pump must supply the following needs:• Fuel delivered to the injectors• Pump backleakage• Fuel in excess of the above to provide pressure

regulation

1 Fuel inlet connection 8 End plate2 Retaining spring 9 Eccentric liner3 Transfer pressure adjuster 10 Blades4 Regulating sleeve 11 Transfer pump rotor5 Peg and spring 12 Distributor rotor6 Regulating piston 13 Rubber sealing ring7 Priming spring 14 Nylon coarse filter

Fig. 6 Cut-away view of regulating valve assemblyand transfer pump.

B Transfer pressure E Feed pressure

Fig. 7 Operation of the transfer pump.

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3.3 Transfer Pump Blades

Refer to Fig. 9The blades may be of carbon, carbon-filled resin, or of steel, depending upon the requirements of the application.Consistency of transfer pressure is more critical with some pump specifications than with others. In these cases, splitsteel transfer pump blades are fitted, with small coil springs between them to maintain blade/liner contact at very low(cranking) speed. As pump speed (and therefore pressure) rises, transfer pressure is applied to the inner ends of the splitblades to maintain contact with the liner. To achieve this, fuel is directed to the blades via branch port "A".

3.4 Transfer Pressure Regulation

Refer to Figs. 6 and 8.

Transfer pressure is transmitted to the underside of theregulating piston through the lower passage to force thepiston upwards. This force is opposed by the forceexerted on the upper face of the piston by the regulatingspring below the peg (5).As transfer pressure rises with increasing engine speed,the piston is forced upwards and the regulating spring iscompressed. Further movement of the pistonprogressively uncovers ports in the sleeve and transferpressure is regulated by permitting a controlled flow offuel back to the inlet side of the transfer pump. Theeffective area of the regulating ports is thus increased asengine speed rises or reduced as speed falls.

A transfer pressure adjuster (3) carries a screw which can be used in one of two ways to provide different control overtransfer pressure:A. "Spring control". As shown in Fig. 6 the adjusting screw abuts a peg which then acts as a stop controlling the

upper position of the spring. This controls the pre-load of the spring and sets the point at which the piston startsto move upwards in response to rising transfer pressure. From that point, as pump speed rises, transfer pressurewill increase in direct proportion to speed increase.

B. "Orifice control". In this case, no peg is fitted and the adjusting screw passes down through the spring to contactthe piston. It is then used to set the upper limit of piston travel, at which point the exposed orifice area becomesfixed. From that point on, as speed (and therefore flow from the transfer pump) increases, pressure will increaseout of proportion to the speed increase. This characteristic is utilised to ensure that timing is fully advanced at highspeed.

B Transfer pressure E Feed pressure

Priming (a) Regulating (b)

Fig. 8 Operation of the regulating valve.

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3.5 Transfer Pressure Relief Valve

Refer to Fig. 9In some cases, when orifice control of transfer pressure is used, it is necessary to limit the maximum transfer pressure,to avoid affecting pump performance and overloading of seals in other areas of the pump.A relief valve, comprising a spring-loaded plunger within a screwed fitting, is located in the pump end plate as shown.Above a pre-determined value, transfer pressure acting upon the plunger is relieved to the inlet side of the transfer pumpas a communicating port is opened.

Transfer Pump

Split Steel Blade

Relief ValveOpen

Fig. 9 Transfer pressure relief valve.

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4.1 Metering Of FuelRefer to Fig. 10.The fuel at transfer pressure passes through passages in the hydraulic head and thence to the metering valve bore (9).The metering valve, operated by the throttle control lever and governor, regulates the flow of fuel through the obliquemetering ports (10) in the hydraulic head and into the pumping section of the rotor.The volume of fuel ("metered" quantity) passing into the pumping element is thus controlled by three factors:i. The position of the metering valveii. The pump transfer pressure.iii. The time during which the rotor inlet ports (6) are aligned with the hydraulic head metering ports (10).

4.2 Charging And Injection

As the rotor (3) turns, and the inlet ports align with the metering ports in the hydraulic head, fuel at metering pressure(C) flows into the central passage in the rotor forcing the pumping plungers (5) apart. The amount of plunger displacementis determined by the amount of fuel which can flow into the rotor while the ports are aligned.This volume of fuel is the metered quantity described above unless the travel of the plungers is limited by the scrollplates, in which case it is under "maximum fuel" condition.With continued rotation, the fuel entering the two metering ports in the hydraulic head is cut off from the inlet ports.The single fuel delivery port (1) in the rotor then registers with an outlet port (2) in the hydraulic head. At the same time,the pumping plungers are forced inwards by the rollers (7) in contact with the internal lobes of the cam ring (8). Fuel,then at injection pressure (A), passes through the central passage of the rotor, the delivery port, and an outlet port tothe related injector.With further rotation, the charging and injection cycles are repeated in sequence with the rotor alternately chargingthrough the metering ports (10) and discharging into each successive outlet port. There is one outlet port for each enginecylinder.

A Injection pressure 5 Pumping plungersC Metering pressure 6 Rotor inlet ports1 Single fuel delivery port 7 Rollers2 Hydraulic head outlet port 8 Cam ring3 Rotor 9 Metering valve bore4 Hydraulic head 10 Hydraulic head metering ports

Charging Injection

Fig. 10 Diagrammatic layout of fuel charging and injection cycles.

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4.3 Hydraulic Head And Rotor Assembly

The hydraulic head and rotor constitute a matedassembly which minimises high pressure leakage whilstallowing sufficient clearance to act as a lubricatedbearing.The hydraulic head comprises a barrel (4), shrunk onto ahardened, alloy-steel sleeve (7). The distributor rotoroutlet port (5) registers, in turn, with each of the deliveryports in the sleeve. These connect with similar passagesin the barrel, into which are screwed the banjo outletconnections. The outlets are equally spaced andpositioned radially around the barrel. The sleeve alsocontains one or, in some cases, two or more meteringports which register with the rotor inlet ports (6). Two ormore ports are used where high flow rates are required.All DPS pumps, except those fitted with a "flatted"metering valve, have a passageway drilled between thetransfer pump chamber and the cambox, and which isfitted with a restricting orifice. Any air trapped within thetransfer pump is released to the cambox through theorifice before the fuel flows to the pumping plungers.The standard distributor rotor (8) has two plungers (9)opposite each other which pump simultaneously as thecam rollers make contact with diametrically opposedlobes on the cam ring.

4.4 Equalisation Groove

Refer to Fig. 11.Certain distributor rotors have an "equalisation" groove, of one of two forms, cut into the surface. The groove (3) shownin Fig. 11, which is in line with the distributor port, ensures that there is a constant residual pressure in all the highpressure lines. This improves the consistency of delivery between the lines, which is particularly important at idlingspeed, to achieve smooth running.The high pressure outlet ports, except for the next to be charged, are connected by the groove and the residual pressurein the line which has just injected is "balanced-out" with the remain ing lines.Alternatively, only the lines immediately before and after the line which is currently injecting may be balanced togetherby changing the design of the groove.

1 Vent orifice 6 Rotor inlet port2 Transfer pump recess 7 Hydraulic head sleeve3 Equalisation groove 8 Distributor rotor4 Hydraulic head barrel 9 Plungers5 Rotor outlet port 10 Drilling to cambox

Fig. 11 Cut-away view of hydraulic head with rotor insitu.

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4.5 High Pressure Outlets

Two types of high pressure outlet may be fitted and they may contain either delivery valves or pressurising valves. Onlyone type of valve will be fitted to a pump.

4.5.1 Delivery valves

Delivery valves comprise a valve with a conical seatlocated within a body, which in turn fits within eachoutlet connection. Their function is to modify the"natural" shape of the speed/delivery curveproduced by the pump to suit the requirements ofparticular engines.The high pressure delivery valves, each screwedinto a banjo connection (2), are fitted around thehydraulic head. Each banjo comprises a deliveryvalve holder (6), valve body (3), valve (4), spring andpeg (5). "Armco" iron washers (1) are used on bothhigh pressure sealing faces of the valve body.Each delivery valve has a small by-pass orificeincorporated to allow fuel to flow back into theequalisation slot in the distributor rotor and effectpressure equalisation at the end of injection.

4.5.2 Pressurising valves

Pressurising valves prevent the pressure in the high pressure line reducing to a very low level after injection, asan aid to smooth running of the engine. They are factory-sealed units.

1 Washers 4 Delivery valve2 Banjo connection 5 Spring and peg3 Valve body 6 Delivery valve holder

Fig. 12 Cut-away view of high pressure deliveryvalve.

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4.6 Axial Outlet Hydraulic Head

A re-designed hydraulic head and rotor assembly isbeing progressively introduced and a typical example isshown in Fig. 13.

The barrel of the new head assembly has an enlargeddiameter at the transfer pump end (1) to accommodatehigh pressure outlets (2), (4), (5) and (6) located axially inthe end face, as shown in Fig. 14.The small holes (3) around the periphery of the barrel arepart of the manufacturing process only and should beignored for service purposes.Although the function of the new assembly isunchanged, a new end plate casting is required toaccommodate the high pressure outlets. Spacerestrictions also require a change to socket-headed endplate screws.The axial outlet arrangement simplifies and strengthensthe area around the hydraulic head. The requirement forsupport plates around the normal banjo bolt outlets, toprevent displacement when tightening high pressurepipe nuts, is also avoided with this design.

Fig. 13 Axial outlet DPS pump

Fig. 14 Axial outlet hydraulic head.

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5.1 Governor ComponentsThe governor comprises a series of flyweights looselyretained within a cage which rotates with the drive shaft.Centrifugal force acts upon the weights in opposition toa spring, the tension of which is varied by the throttlelever as more or less power is demanded from theengine.The flyweight assembly (9) is mounted on the drive shaft(10). Rubber inserts are positioned between the drivingand driven lugs on the shaft and flyweight assembliesrespectively. These inserts cushion the weights fromtransitory shaft reactions to pumping forces which wouldotherwise affect fuel delivery.Movement of the flyweights actuates a thrust sleeve (8).The sleeve, sliding along the drive shaft, causes thegovernor arm (7) to pivot about a fulcrum on the controlbracket (5). This movement is transmitted by thegovernor link (4) to the metering valve (3). Rotation of themetering valve changes the flow area between thegroove in the valve and the metering port, thuscontrolling the quantity of fuel which enters the port.The governor link arm and spring are located in the upperpart of the pump, enclosed by the control cover whichalso houses the throttle shaft (1) and the idling shaft (12).

5.2 Two-Speed Governor

Refer to Fig. 15A two-speed governor provides rapid response to pedal movement and gives driving characteristics comparable to thoseof a petrol-engined vehicle of similar power.At idling speeds, the position of the metering valve is controlled by the force generated by the weights which, via thegovernor arm, compresses the idling leaf spring (6) against the idling actuator (11) until equilibrium is achieved. Idlingspeed is set by adjustment of the idling screw (not shown) which, in turn, positions the shaft and the actuator.At intermediate speeds, the spring pack tube links the vehicle accelerator pedal directly to the metering valve, so thatfuel delivery is entirely a function of the throttle lever position.As maximum speed of the engine is approached, and with the throttle lever towards the maximum speed stop, theforce of the flyweights exceeds the pre-load of the governor main spring and the metering valve is rotated to reduce theamount of fuel delivered.

5.3 All-Speed Governor

Refer to Fig. 15.An all-speed governor is fitted if there is a need to govern over the whole operating speed range e.g. on tractorapplications using power take-off. In such cases the pre-loaded spring and sleeve assembly (14) of the two-speed versionis replaced by simple coil spring. At any speed above idling, the coil spring is extended and, as speed increases, theweights move the arm, closing the metering valve until equilibrium is achieved. Governing is thus provided at anyintermediate speed between idling and maximum.

1 Throttle lever shaft 8 Thrust sleeve2 Linkage hook 9 Governor flyweight

assembly3 Metering valve 10 Drive shaft4 Governor link and spring 11 Idle actuator5 Control bracket 12 Idling lever shaft6 Idling leaf spring 13 Anti-stall device7 Governor arm 14 Main governor spring

Fig. 15 View of two-speed mechanical governor.

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5.4 Anti-Stall Device

Refer to Fig. 15.When the throttle lever is "closed" rapidly, the load on the governor spring assembly is released. The reduction of springtension allows the governor arm to move the metering valve to the "no-fuel" position. Engine speed will decrease rapidlyand, unless the system recovers rapidly to the "idling fuel" position, the engine may stall.A light spring (13), fitted between the governor arm and the governor spring front anchorage, damps out the closingmotion of the governor linkage. This aids rapid re-opening of the metering valve before the engine stalls.Some pump specifications may have an anti-stall screw fitted which is set to be just out of contact with the governorarm at idling speed. This limits the movement into the "no-fuel" region during deceleration.All-speed governors may not require an anti-stall facility, thus avoiding the need for the leaf spring, actuator and idlingshaft. The small spring (13) then acts as an idling spring and idling speed is set by the throttle lever minimum speedscrew.

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6.1 Scroll Plate OperationScroll plates (9), with matching internal profiles, are located each side of the cam ring (8). A slot in the rim of each scrollplate engages with a link plate (11), which slides transversely in a slot in the governor control bracket. Movement of thelink plate varies the position of the scroll plates relative to the cam ring.Depending upon the position of the scroll plate profiles relative to those of the cam ring, the outward travel of the rollersis varied to permit either excess fuel or normal maximum fuel delivery.

A Scroll plates in the excess fuel position with throttle lever closed 6 Scroll plate profilesB Scroll plates in the maximum fuel position with throttle lever open 7 Roller and shoes1 Anti-stall stop 8 Cam ring2 Throttle control-lever 9 Scroll plates3 Excess fuel linkage spring 10 Maximum fuel adjusting screw4 Inner tongue - link plate 11 Link plate5 Excess fuel shaft and lever 12 Link plate spring

Excess Fuel (a) Maximum Fuel (b)

Fig. 17 Schematic view of scroll plate mechanism with mechanical excess fuel.

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6.1.1 Excess fuel position

At cranking speeds the scroll plates are automatically positioned so that the excess fuel profile corresponds withthe rotor filling stage. The cam ring is in the fully-retarded position.As the rotor filling port opens, metering pressure forces the plungers and cam rollers outwards to meet the profilesof the scroll plates at point (a). The rollers continue to open outwards against the scroll profiles until the fillingport closes at point (b) on the excess profile. The rollers then contact the cam ring at point (c) and deliver fuel inexcess of the normal maximum.

Excess Fuel Position

Maximum Fuel Position

Delivery Port Rotor Filling Port Delivery PortOpens Closes Opens Closes Opens

Path of roller

Scroll plate profile

Cam ring profile Commencement of excess fuel profile

Fig. 16 Schematic diagram of scroll plate phasing.

6.1.2 Maximum fuel position

Refer to Fig. 16.When excess fuel is disengaged, the scroll plates are rotated to the maximum fuel position and the cam ring isrotated to a position determined by the automatic advance unit. As the rotor filling port opens, metering pressureforces the cam rollers outwards to meet the profile of the scroll plates at point (d).The cam rollers continue to move outwards, remaining in contact with the retracting scroll profiles until the fillingport closes at point (e), this being the maximum fuel position set by the adjusting screw (10) as shown in Fig. 16.With metering pressure to the pumping plungers now terminated by filling port closure, the rollers are free toleave the scroll plate profiles and 'float' until contact is made with the cam lobe at point (f). This is the point atwhich fuel injection commences via the now-open delivery port.

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6.2 Mechanical Excess Fuel

Refer to Fig. 16.Movement of the link plate is controlled in one direction by the excess fuel shaft (5) through spring linkage (3) connectedto the throttle lever (2), and in the opposite direction by a link plate spring (12).At engine cranking speeds, when automatic excess fuel is required, the throttle lever must be closed against the anti-stall stop (1). The spring linkage will have rotated the excess fuel shaft so that the lever displaces the link plate againstthe spring. At the same time the scroll plates are rotated against the direction of pump rotation. The scroll profiles (6)on the internal rims of the plates then allow the pumping plungers to move further apart, admitting fuel in excess of thenormal maximum. As soon as the engine becomes self-sustaining, excess fuel delivery is terminated by the action ofthe governor on the metering valve, reducing the fuel level to that required for idling.When the throttle is moved away from the idling position, the control lever (2), through the linkage spring (3), rotatesthe excess fuel shaft and lever (5) away from the inner tongue (4) on the link plate (11). This allows the spring (12) tomove the link plate and scroll plates transversely in the direction of pump rotation to the maximum fuelling positionagainst a pre-set adjusting screw (10). In this position, the profiles (6) on the internal rims of the scroll plates (9) checkthe outward movement of the rollers and shoes (7), in contact with the pumping plungers, to the normal maximum fuellevel.

6.3 Hydraulic Excess Fuel

This device (1), as shown in Fig. 18, is built into thegovernor cover and is controlled by the action of the latchvalve.

At engine cranking speeds (see Fig. 19), the latch valve is closed and port C is covered, isolating the excess fuel device.The spring-loaded piston abuts the cover plug of the device and the scroll link plate is retained in the excess fuel position.Fuel at transfer pressure flows into the latch valve bore and passes through two orifices A and B to the cambox. Theintermediate pressure, created between the orifices, together with the spring load on the valve head, keeps the valveclosed.When the engine starts, transfer pressure increases, overcoming the intermediate pressure and the spring pre-load, andlifts the latch valve. Orifice A is thus cut off from the cambox return circuit, the intermediate pressure reduces to camboxpressure and the valve opens rapidly, allowing fuel at transfer pressure to act upon the excess fuel piston. This overcomesthe excess fuel spring pre-load and movement of the piston allows the link plate to move to the normal maximum fuelposition under the action of the link plate return spring. Simultaneously, transfer pressure is communicated to theadvance device, moving the advance piston away from the retard position.

1 Hydraulic excess fueldevice

2 Torque control device

Fig. 18 DPS pump with hydraulic excess fuel andtorque control.

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At normal running speeds, transfer pressure holds the latch valve open, preventing excess fuel re-engagement. Whenthe engine stops, transfer pressure reduces to zero and the valve closes, thus allowing automatic start-retard and excessfuel on restarting.

Engine Cranking Engine RunningExcess Fuel Device Piston

Scroll Link Plate

Latch Valve

To Advance Device

To Advance Device

Fig. 19 Operation of the hydraulic excess fuel device.

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6.4 Torque Control

This device (2), as shown in Fig. 18, is built into thegovernor cover.Maximum fuel delivery is determined by the position ofthe sliding link plate (2) which engages the scroll plates.When a torque control device is fitted, this position is setby a bell-crank lever (9) which abuts a stop (3) formed onthe link plate. The position of the lever is controlled bythe plunger (8).Fuel at transfer pressure, rising with increasing pumpspeed, flows via the latch valve to disengage the excessfuel device. A communicating port to the torque controldevice directs transfer pressure to the head of the spring-controlled plunger.

At low speeds, three springs combine with transferpressure to control plunger displacement and themaximum fuel level rises as speed increases. At a pre-determined speed, the plunger head abuts the springguide and the centre spring becomes ineffective (point'A' ). Further plunger movement is then controlled by theother two, stronger, springs. Therefore, in the upperengine speed range, maximum fuel delivery rises at alower rate until the spring guide abuts the stop shoulderat a point corresponding approximately to maximumspeed point 'B'.Torque control spring loads and plunger travel areadjusted to meet engine performance requirements.

1 Link plate spring 6 Spring guide2 Scroll link plate 7 Stop shoulder3 Link plate stop at low

speed8 Plunger

4 Link plate stop at highspeed

9 Bell-crank lever

5 Plunger head

Excess Fuel Device

Torque Control Device

Fig. 20 Operation of the torque control device.

Maximum fuel curve

Fixed scroll plate curves Three-

spring control

Two-spring control

Speed (rpm)

Fuel

Del

iver

y

Fig. 21 The effect of torque control

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6.5 Turbocharger Boost Control

Exhaust-driven turbochargers fitted to diesel enginesraise inlet manifold pressure and enable a greater massof air to be introduced during the induction cycle. This,in turn, enables a larger quantity of fuel to be injectedand burnt, thereby increasing the power output from agiven size of engine.However, turbochargers have low efficiency at lowengine speeds. It is therefore necessary to reduce thelevel of extra fuel introduced at lower engine speeds tomaintain acceptable exhaust emissions. To achieve this,a "boost control" device (1) is incorporated into pumpapplications used with turbochargers.

Typically, the effect of the boost control on theturbocharged level of maximum fuel is as shown on thegraph.

Fig. 22 DPS pump with boost control.

Fixed scroll plate curves

Boost control operation

Maximum fuel curve at “no boost”

Speed (rpm)

Fuel

Del

iver

y

Maximum fuel curve at “full boost”

Fig. 23 The effect of boost control

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The boost control device is fitted in place of the normalmaximum fuel adjusting screw. It comprises a spring-loaded diaphragm in a sealed housing which is fitted toa modified governor cover. The operation of the unit isillustrated in the diagram opposite.The diaphragm (7) moves between fixed stops and isactuated by boost pressure transmitted from aconvenient point on the engine inlet manifold to the inletconnection (1).The diaphragm acts on a fuel control rod (6) in oppositionto the spring (3) which abuts the sliding link plate andadjusts the level of maximum fuel by rotation of the scrollplates (5). The position of the stroke adjuster (4)determines the travel of the fuel control rod, describedas "boost" travel in the diagram opposite. This travelrepresents a change in fuel delivery level associated withthe two "fixed scroll plate" curves shown in Fig. 23.Shimming of the control spring (3) will set the speed atwhich fuel delivery increases due to boost controloperation (point 'A' in Fig. 23).The maximum fuel adjusting screw (8) sets themaximum fuel delivery at full boost.Backleakage from the pump housing along the fuelcontrol rod is relieved by a connection (2) to the innerchamber and fed back to the fuel tank at atmosphericpressure.

1 Boost pressure inlet 5 Scroll plate2 Backleak connection 6 Fuel control rod3 Control spring 7 Diaphragm4 Stroke adjuster 8 Maximum fuel adjusting

screw

Zero Boost Position

Maximum Boost Position

“Boost” travel

Fig. 24 Operation of the boost control unit.

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7.1 Automatic Advance And Start Retard DeviceThis device progressively advances the commencementof injection as engine speed increases and mayincorporate an automatic start-retard system thatoperates at cranking speeds.Automatic advance is controlled by a piston (8) whichslides in the advance housing (7) mounted on theunderside of the pump housing (2). The movement of thepiston is transferred through the cam advance screw (9)to the cam ring (4) which rotates freely in the pumphousing. The advance spring (12) is located between thespring plunger (11) and the spring end cap (13) andcontrols the position of the piston by balancing the effectof fuel at transfer pressure in the chamber (5) on theadvance piston (8). Fuel at transfer pressure enters thechamber via a drilling and a ball valve in the headlocating fitting (see item 3, Fig. 26) (which also securesthe advance device to the pump body).Start-retard is controlled by the first stage low-ratedspring (10) which is located between the hollow end ofthe piston and the spring plunger. When the engine isstationary and the latch valve is closed, there is nopressure acting on the piston. Under the pre-compression of the advance spring and first stage(retard) spring (10), the piston rests against the pressureend plug (6); the system is therefore in the fully retardedposition.On starting, when transfer pressure from the pumpopens the latch valve, pressure In the chamber (5) actingon the piston compresses the first stage (retard) spring(1 0) and the system reverts to the normal speed advancemode of operation.As engine speed increases, the transfer pressure actingon the piston moves it along the bore and compressesthe advance spring. This causes the piston and cam ringto move in the opposite direction to pump rotation andprogressively advance the commencement of injection.

When engine speed is reduced, the transfer pressure drops and the normal leakage of fuel past the piston permits thedevice to return towards the retard position under the action of the advance spring.

7.2 Manual Idling Advance Device

Refer to Fig. 25.In conditions of low ambient temperature, engines (once started) may require additional injection advance to improvecold idling combustion stability. To meet this requirement, a driver-operated manual advance device can be incorporated.The manual cold idling advance lever (17) can be operated through a cable control by the driver. The lever is attachedto a spring-loaded spindle (16) located by three steel balls (15) on the detent plate (14). When the lever is moved, it risesover the three balls and the spindle is pulled outwards, together with the spring plunger (11) away from the advancepiston (8). This allows the advance piston and cam ring (4) to move beyond the normal advance position at idling speedwhen the latch valve has opened and fuel at transfer pressure is applied to the piston.

1 Roller and shoe 11 Spring plunger2 Pump housing 12 Advance spring3 Plungers 13 Advance spring end cap4 Cam ring 14 Detent plate5 Transfer pressure chamber 15 Balls6 Pressure end plug 16 Spindle7 Auto-advance housing 17 Manual cold idling

advance lever8 Piston 18 Spindle spring9 Cam advance screw 19 Distributor rotor10 1st stage (retard) spring

Fig. 25 Sectioned view of auto-advance and start-retard unit with manual cold idling advance lever.

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7.3 Head Locating Fitting (And Damper Assebly, When Fitted)

On the underside of the pump, the head locating fitting(3) is screwed into the hydraulic head (2) and, inconjunction with the stud and nut (9), secures theadvance unit (8) against the pump housing. It alsopositions the hydraulic head correctly in the housing andconnects the fuel passages in the head with the advanceunit.The assembly contains a non-return ball valve (5) tohydraulically lock the advance unit as the rollers contactthe cams. Otherwise, during the injection phase, therollers would tend to turn the cam ring (10) in the retarddirection, affecting timing and injection rate.The by-pass hole (4) serves as a local hydraulic damperto attenuate pressure peaks and avoid damage to theseals (7). A damper assembly (6), when fitted, is anintegral part of the head locating fitting and comprises aspring steel diaphragm in a sealed housing. It is fitted onsome applications to dampen fluctuations of transferpressure which would otherwise result in inconsistencyof rotor filling pressure and line-to-line deliveryvariations.

7.4 Servo-Assisted Advance Device With Externally Controlled Light Load Advance

Refer to Fig. 27.Injection timing is varied by moving the cam ring via the cam screw which engages the advance piston. When pumping,cam reaction forces on the piston are opposed by transfer pressure at a level dependent on speed and servo valveposition. A ball valve locks off fuel in the outer chamber during pumping to stabilise piston movement.Cranking: In this mode of operation, transfer pressure is too low to open the latch valve which controls fuel supply tothe advance device. The advance piston is therefore driven against the plug (1) giving full retard.Advancing: As speed increases, transfer pressure rises, the latch valve opens, the servo valve is displaced and fuelflows to the inner and outer chambers. This moves the advance piston and cam ring in the opposite direction to pumprotation and advances the timing. Advance continues until equilibrium is achieved when spring force stops the servovalve, restricting flow to the outer chamber.Retarding: As speed decreases, transfer pressure falls, the servo valve closes the passage to the outer chamber andopens a passage (2) to the cambox releasing fuel from the chamber. Injection retards until the servo valve restoresequilibrium.

1 Distributor rotor 6 Damper assembly2 Hydraulic head 7 O-ring seals3 Head locating fitting 8 Automatic advance and

start-retard unit4 By-pass hole 9 Dome nut5 Ball valve 10 Cam ring

Fig. 26 Sectioned view of head locating fitting anddamper assembly.

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Cranking Advancing Retarding

Light Load

Full Load

Rocking Lever

Servo Advance

Advance Piston

Servo Valve

Inner Chamber

Outer Chamber

CIA Plug

CIA Shaft and Pin

Fig. 27 Operation of the servo-assisted advance device with externally-controlled light load advance.

Light load advance is achieved by a cam on the throttle lever which actuates the rocker arm, which in turn abuts theservo spring plunger. Lever movement towards idling relieves spring load, transfer pressure displaces the valve andtiming is advanced. Fig. 28 illustrates these components on the HSDI DPS pump.

1 Fast idle linkage 4 Throttle lever2 Idling lever 5 Light load advance rocking lever3 Light load advance cam

Fig. 28 High speed direct injection (HSDI) DPS pump .

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7.5 Cold Idle Advance (CIA) And Fast Idle

A slotted piston in the CIA plug is linked, via a shaft andlever, to an engine temperature sensor. When cold, theslot (1) aligns with plug drilling (2). As the engine starts,fuel displaces the CIA piston until the slot end abuts theshaft pin, moving the advance piston beyond the normalrunning position to stabilise combustion at idling speed.When hot, the CIA piston is rotated, slot (1) moves fromdrilling (2) and aligns with groove (3) in the plug. Fuelbleeds from the piston to the outer chamber, restoringnormal advance.An engine temperature sensor, termed a 'waxstat' , isattached to a cable which controls the position of the CIAand the fast idle linkage ((1) in Fig. 28). Hence, when theengine is cold and the CIA is operative, the idling lever((2) in Fig. 28) is simultaneously moved to lift the idlingspeed screw from its stop on the housing. This raises theidling speed until normal running temperature isachieved and the waxstat relaxes.

1 Slot 3 Groove2 Drilling

CIA Engaged

CIA Disengaged

Fig. 29 Operation of the cold idle advance (CIA).

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8.1 Pump Drive ShaftThe pump drive is a solid one-piece shaft (8) carried intwo bearings (7) and (10).Drive to the distributor rotor (5) is through an inner slotin the driving head (6) which engages with the driventang on the rotor. Two or four opposed pumpingplungers (2), within the head of the rotor, contact theshoes (4) and rollers (3). Each shoe slides radially in theouter slots of the drive shaft. Outward movement of theplungers during the filling cycle brings the rollers intocontact with the scroll plate profiles under excess andmaximum fuel conditions only. At all other times whenthe engine is running, outward movement is limited bythe volume of metered fuel.The rollers only contact the cam ring during the pumpingcycle.Long and short spacers (1) are located one in each sideof the driving head (6) and allow only one position ofengagement for the tang on the rotor (5). The spacersalso act as guides for the roller shoes.

8.2 Latch Valve

Refer to Fig. 31.The latch valve (1), comprises a spring-loaded valve with a central drilling, fitted in a threaded body which also retainsthe hydraulic head in the pump housing.At cranking speed (a), the latch valve is closed and serves to delay advance by preventing transfer pressure (B) reachingthe advance unit pressure chamber (11) and the rotor vent switch valve (12), both of which remain at cambox pressure(F).When the engine becomes self-sustaining (b), increased transfer pressure on the underside of the latch valve opens thevalve against its spring and allows fuel at transfer pressure (B) to flow through a cross-drilling in the valve body to thepressure chamber in the advance unit.There are two types of latch valve; differential and non-differential.i. Differential: (See Fig. 19) This type of valve is required when an engine needs to remain in the "excess fuel and

start-retard" mode at a speed higher than normal idle during starting.The operation of this type of latch valve is described in detail in section 6.3. The intermediate pressure requiredfor its operation is created between orifice "A" (within the valve), and orifice "B", (in the passageway to the cambox).The valve will close at a lower pump speed than that at which it opened, i.e. when transfer pressure no longerexceeds the combined effect of spring force and cambox pressure.

ii. Non-differential: This type of latch valve does not require intermediate pressure, and the fuel may return directlyto either cambox or inlet (feed pressure). The valve does not contain a central drilling or an orifice and there is nosecond orifice in the passageway to the cambox. The valve will close at the same speed at which it opened.This type of valve may be used on engines where the latching speed can be lower than that at normal idle.

Note:Fig. 31 depicts the operation of a differential-type latch valve. If it were to depict a non-differential type, the 'intermediatepressure' (D) would become 'cambox pressure' (F) or 'feed pressure'.

1 Spacer 6 Drive shaft head2 Pumping plunger 7 Rear bearing3 Roller 8 Drive shaft4 Shoe 9 Pump housing5 Distributor rotor 10 Front bearing

Fig. 30 View of pump drive shaft

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8.3 Rotor Vent Switch Valve

The rotor vent switch valve comprises a spring-loaded valve within a body which, like the latch valve, also functions asa hydraulic head retaining bolt.At engine cranking speeds (a), when the rotor self-venting feature is in operation, the latch valve (1) is held closed andthe passage to the rotor vent switch valve is at cambox pressure (F). The valve in the rotor vent switch is held open byits spring.Self-venting of the rotor (3) (in the case of a 4 cylinder pump) occurs at four intervals of 23° every pump revolution, whena small drilling (8) in the hydraulic head sleeve communicates in turn with each of the rotor inlet ports (9).For the first 12° of rotation, any retained air is forced through the vent orifice (8) by residual pressure in the rotor (3) fromthe previous pumping cycle. For the remaining 11° of rotation there is a direct communication between the vent orificeand the two oblique metering ports (7) in the hydraulic head (4) and air is again forced at metering pressure (C) throughthe orifice. From this orifice air/fuel travels through passages in the hydraulic head at cambox pressure (F) across therotor vent switch valve (12) to the cambox.When the engine becomes self-sustaining (b), transfer pressure (B) opens the latch valve and allows fuel at this pressureto reach the rotor vent switch valve, which then closes against its spring thus isolating the venting passage from thecambox.

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B Transfer pressure 7 Hydraulic head metering portsC Metering valve 8 Vent orificeD Intermediate pressure 9 Rotor inlet portsF Cambox pressure 10 Plunger1 Latch valve 11 Auto-advance pressure chamber2 Inlet from transfer pump 12 Rotor vent switch valve3 Distributor rotor 13 Head locating fitting4 Hydraulic head 14 Ball valve5 Return to cambox 15 Cam ring6 Metering valve 16 Roller and shoe

Engine Cranking (a) Engine Running (b)

Fig. 31 Diagrammatic layout showing fuel pressures to the latch valve and the rotor switch valve.

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8.4 Cambox Pressurising Valve

Some pump specifications require a small positivepressure within the cambox when the pump is running.This pressure is maintained by partial restriction of thepump backleak flow by a spring-loaded ball valve, whichmay be screwed directly into the governor cover (4), orinto an intermediate adaptor.Cambox pressure prevents the ingress of dirt into thepump and provides smoother governor run-outcharacteristics.The ball valve (2) is held against the seat (3) by the spring(1) until backleak flow rate increases with increasingpump speed to raise cambox pressure, overcome thespring force and open the valve, thus limiting themaximum pressure. During cranking, when transferpressure is very low, the small orifice in the seat allowsfuel to escape, therefore stopping cambox pressurerising sufficiently to oppose transfer pressure and thusprevent filling of the pumping plungers. It allows any airtrapped within the cambox to escape.The spring (5) acts as a filter and prevents blockage ofthe orifice by any debris.

8.5 Solenoid Shut-Off

An electrically-operated fuel shut-off is screwed into thetop of the hydraulic head. The unit consists of a solenoidassembly which controls a spring-loaded armature andvalve. The valve is located between the transfer pumpoutlet and the metering valve.When the solenoid is energised, on starting the engine,the armature lifts the valve against spring pressure andallows fuel at transfer pressure to pass to the meteringvalve. When the solenoid is de-energised (by cutting theelectrical supply), the spring returns the valve to its seatand prevents the rotor from filling, thereby stopping theengine. The pump must be at rest (with no transferpressure) before the valve can be re-opened.

1 Upper spring 5 Lower spring2 Ball valve 6 Copper washers3 Valve seat 7 Backleak connection4 Governor control cover

Fig. 32 Sectioned view of pressurising valveassembly.

1 Solenoid 4 Armature2 O-ring seal 5 Valve3 Spring

Fig. 33 Exploded view of solenoid operated fuel shut-off valve.

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8.6 External Mechanical Stop

In addition to the solenoid shut-off valve, there issometimes a requirement to provide a separate,mechanical, means of stopping fuel delivery. Forexample, some vehicles utilise an exhaust brake whichoperates by the closure of a valve in the exhaust systemto create a back-pressure against which the engine actsas a pump. In such cases, the exhaust brake mechanismis linked to a stop lever (1) on a shaft in the DPS governorcover to ensure that no fuel is injected when the deviceis operating.

The stop lever operates, via an internal pawl (1), directlyonto the metering valve pin (2), moving the valve into the"stop" (no-fuel) position.

Fig. 34 DPS pump with external mechanical stop.

1 Pawl 2 Metering valve pin

Running Position Stop Position

Fig. 35 Metering stop control.

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8.7 "Flatted" Metering Valve

A metering valve which has a closely-controlled taperedflat area (1) machined in line with the fuel control slot (2)avoids the need for a rotor vent switch valve. It allowsany air from the transfer pump to be vented to thecambox.Pumps equipped with this valve have no rotor ventswitch valve or any of the associated communicationdrillings to the hydraulic head, cambox or latch valve.Fig. 37 illustrates a typical hydraulic fuel circuit whichincorporates this design change.

1 Flat 2 Fuel control slot

Fig. 36 Metering valve with vent "flat".

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A Injection pressure 6 Transfer pumpB Transfer pressure 7 Regulating valveC Metering pressure 8 Pressure relief valveD Intermediate pressure 9 Latch valveE Feed pressure 10 Latch valve orifice B (see Fig. 19)F Cambox pressure 11 Head locating fittingG Backleakage 12 High pressure outlet connection1 Hydraulic excess fuel valve 13 Cold idle advance2 Torque trimmer 14 Servo valve3 Cambox pressurising valve 15 Advance piston4 Metering valve 16 Scroll plates5 Stop solenoid 17 Pumping plungers

Fig. 37 Hydraulic fuel circuit for the HSDI DPS pump.

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9.1 Abbreviations Used In This Manual° degreesCIA Cold Idle AdvanceDI Direct InjectionDPS Diesel Pump SFig. FigureHSDI High Speed Direct InjectionIDI InDirect Injection

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IX APPENDIX

NOTES

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Il a été apporté une attention particulière pour garantir l'exactitude des renseignements contenus dans cette publication par Delphi Diesel Systems Ltd., maisla société décline toute responsabilité légale à cet égard. Delphi Diesel Systems Ltd. poursuit un programme intensif de conception et de développement

qui peut entraîner la modification des spécifications des produits. Delphi Diesel Systems Ltd. se réserve le droit de modifier les spécifications, sans pré- avis et si cela est nécessaire, pour assurer les performances optimales de sa gamme de produits.

Tous droits réservésToute reproduction, mémorisation dans un système informatique ou transmission sous quelle que forme que ce soit, ou par tout moyen électronique,

mécanique, par photocopie, enregistrement ou autre de cette publication est interdit sans l'autorisation préalable de Delphi Diesel Systems Ltd.

Ainda que se tenha lido o máximo cuidado na compilação da informação contida nesta publicação, a Delphi Diesel Systems Ltd., não pode aceitar qualquerresponsabilidade legal por inexactidões. ADelphi Diesel Systems Ltd. tem um programa intensivo de projecto e desenvolvimento qe pode porventuraualterar as especificações do produto. ADelphi Diesel Systems Ltd. reserva o direito de alterar especificações sem aviso e sempre que seja necessario

para assegurar um desempeho óptimo da sua linha de produtos.Todos os direitos reservados.

Nenhuma parte desda publicação pode se reproduzida, armazenada num sistema de onde possa ser recuperada ou transmitida de alguma forma, ou porquaisquer meios, electrónico, mecânico, de fotocópia, gravação ou outros, sem autorização antecipada de Delphi Diesel Systems Ltd.

Whilst every care has been taken in compiling the information in this publication, Delphi Diesel Systems Ltd. cannot accept legal liability for any inaccuracies.Delphi Diesel Systems Ltd. has an intensive programme of design and development which may well alter product specification. Delphi Diesel Systems Ltd.

reserve the right to alter specifications without notice and whenever necessary to ensure optimum performance from its productrange. All Rights Reserved

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form, or by any means, electronic, mechanical, photocopying,recording or otherwise, without the prior permission of Delphi Diesel Systems Ltd.

Aunque hemos tomado todas las precauciones necesarias al recopilar esta publicación, Delphi Diesel Systems Ltd. no acepta ninguna responsabilidad legalpor inexactitudes que puedan aparecer en la misma. En Delphi Diesel Systems Ltd. se sigue un programa intensivo de diseño e investigación el cual podríaen cualquier momento alterar la especificación de los productos. Delphi Diesel Systems Ltd. se reserva el derecho de alterar las especificaciones

sin notificación previa y siempre que esto sea necesario para asegurar el mejor funcionamiento posible de sus productos.Todos los Derechos Reservados

No se permite copiar, almacenar en sistema recuperable ni transmitir esta publicación de ninguna forma o medio electrónico, mecánico, de fotocopia, grabación o cualquier otro, sin autorización previa de Delphi Diesel Systems Ltd.

Bei der Zusammenstellung der in dieser Veröffentlichung enthaltenen Informationen wurde mit größtmöglicher Sorgfalt vorgegangen. Delphi Diesel SystemsLtd. kann jedoch rechtlich nicht für etwaige Ungenauigkeiten zur Verantwortung gezogen werden. Delphi Diesel Systems Ltd. führt ein forlaufendes Designund Entwicklungsprogramm durch, weshalb es möglich ist, daß sich Produkdaten ändern. Delphi Diesel Systems Ltd. behält sich das Recht vor, ohne

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übertragen werden.

Anche se ogni cura è stata adottata nel compilare le informazioni di questa pubblicazione, Delphi Diesel Systems Ltd. Declina qualsiasi responsabilità pereventuali imprecisioni. Delphi Diesel Systems Ltd. svolge un intenso programma di progettazione e sviluppo che potrebbe modificare le specifiche del prodotto.Delphi Diesel Systems Ltd. si riserva il diritto di modificare le specifiche senza preavviso e ogniqualvolta lo ritenga necessario ai fini assicurare le prestazioni

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Nessuna parte di questa pubblicazione può essere riprodotta, memorizzata in un sistema elettronico o trasmessa in qualsiasi forma o con qualsiasi mezzo,elettronico, di fotocopiatura, di registrazione o altro, senza previa autorizzazione di Delphi Diesel Systems Ltd.