3.3 Details


3.3.1 Hydraulic head rotor

Withdraw the rotor from the hydraulic head. Examine the running surface very closely for signs of erosion, particularly the area around the delivery port. If severe erosion is evident, the head and rotor assembly must be replaced.

3.3.2 Hydraulic head plungers

If damage to the plungers is suspected, carefully separate the plungers from the rotor, one at a time, and inspect them for scoring or other damage. Clean each plunger with test oil and immediately replace it very carefully in its original bore, the same way round.

The recommended plastic retainer or short lengths of clean nitrile rubber tubing should be used to retain the plungers in their bores. Replace the hydraulic head if the plungers show severe scratching.

If the plungers are stepped, they are fitted with the smaller diameter in towards the centre of the rotor. If they are of different lengths the two longer plungers are fitted in line with the axis of the rotor delivery port.

3.3.3 Cam ring and scroll plates

Inspect the running surface of the cam ring and scroll plates for signs of breakdown of the leading face or apex of the profile. If there are significant signs of pitting or "smearing" they must be replaced as a set. Smearing is the result of failure of the surface due to abrasion or overloading, which may be due to excessive hydraulic pressure (possibly caused by nozzle blockage).

3.3.4 Rollers and shoes

Inspect rollers and shoes for damage. Pay particular attention to the condition of the contact surfaces and check that the rollers rotate freely in their shoes. If the cam ring has failed, the rollers and shoes may also have been severely damaged. If satisfactory, rollers must be replaced in their original shoes.

3.3.5 Transfer pump

Check blades for chips, scores or breakages. Blades may be of carbon, resin-bonded carbon, or sintered steel. Resin-bonded blades have an identification groove in the base of the central slot. Carbon blades have no groove.

Blades must be replaced in sets and must be of the same type as the originals. Examine the transfer pump rotor for wear or damage.

3.3.6 End plate and transfer pump liner

Examine the inner face of the end plate for wear. Replace it if there is any significant scoring. If a separate sandwich plate is fitted. and it is scored or worn, it must be replaced and not reversed.

Examine the liner for corrosion or scoring and replace it if there are any signs of damage.

3.3.7 Control valves

Check all control valves for wear or scoring. Examine the metering valve for "stepping" of the control slot edges and at the point where it enters the bore in the hydraulic head. Check that the valve and the governor link pin are securely fixed in the bar. Check the regulating valve, latch valve and rotor vent switch valve for damage or corrosion and blockage of orifices.

3.3.8 Delivery valves and cambox pressurising valves

Check for defects in delivery valve assemblies. If movement of the valve can be detected when shaken, the spring may have collapsed, in which case it should be replaced. lnspect the cambox pressurising valve (if fitted) for wear and damage, particularly the spring, valve and filter spring.

3.3.9 High pressure outlet pressurising valves

A) Outlets on "radial" hydraulic heads

(i) "Piston" type:

The outer end of the rollpin should be either flush with the end of the banjo bolt or outlet connector body, or recessed by no more than 0.8rnm. Test the freedom of the valve by pushing a thin rod through the centre of the rollpin.

(ii)"Ball" type:

In the 7139-183 series, the balls should be either flush with the outer face of the valve body or protrude by no more than 1.2mm. Examine the balls for damage or signs of corrosion.

Use a suitable piece of brass rod to push each ball into its holder against the spring to check for freedom of movement. If one assembly is faulty, replace the whole set.

B) Outlets on "axial" hydraulic heads

Only the "ball" type of pressurising valve is used and, in the 7185-022 series, the balls should be either flush with the outer face of the valve body or protrude by no more than 0.5mm (see Service Instruction Note D014 for full details of both types of valve).

3.3.10 Springs

Look for distorted or fractured springs. Very carefully examine the areas of contact with adjoining components (spring pegs, throttle shaft links etc).

Check that all springs specified in the Parts List for the pump are present.

3.3.11 Fittings and threads

Check all screws and nuts for damage. Check the cam advance screw flats, which may have been damaged by careless application of the high tightening torque.

Check all threads for damage, especially on the transfer and distributor rotors, hydraulic head, cam advance screw hole, studs, fuel inlet and return and high pressure outlet connections.

3.3.12 Linkages

lnspect all mechanical governor linkages, shafts, pivot pins and arms for wear, cracks or scoring of their mating surfaces.

Examine the cold idle advance spring-loaded plastic link for breakage.

3.3.13 Control shafts

Examine control shafts and their associated bores in the governor cover for distortion, wear, looseness of joints or elongation of spring anchor holes. The items in this group are; the excess fuel shaft, idling and manual idling advance shafts, speed control, manual stop, and their associated levers and linkages.

3.3.14 Drive shaft and associated component

lnspect the shaft for wear or damage, especially where the oil seal(s) contacts the shaft. Check splines and keyways for cracks or chipping.

Examine the thrust surfaces on the inner face of the pump housing and the weight cage for damage or scoring.

Examine the governor weight cage and weights for wear, cracks, or damage. Ensure that the correct number and

type of governor weights are fitted.

3.3.15 Advance device

Examine the components for corrosion. If water has been present in the fuel, it will tend to settle in the advance


Check that pistons move freely.

3.3.16 Levers and external controls

Examine all levers for excessive wear at contact points and for cracks.

Examine the HSDI light load advance cam for excessive wear.

3.3.17 Pump housing

Examine the housing for damage, especially to the sealing surfaces. II the bearing is unfit for further service, the

housing must be replaced.

3.3.18 Orifices

Examine all orifices for blockage and carefully clear any obstruction with dry compressed air.

3.3.19 Electrical connections

Ensure that all electrical solenoid parts are clean, especially the connection(s), and that the plunger is free in its

bore. Check that the flexible valve seat is in good condition, with no pitting or other damage.

if any fault is apparent in the stop solenoid assembly, the whole unit must be replaced as the plunger is matched to the body.

3.3.20 Oversize metering valves

Some DPS pumps are fitted with hydraulic heads having an oversize metering valve bore and an oversize metering valve to suit. Pumps fitted with such heads have the number 6.375 etched between the outlet connections adjacent to the metering valve bore. The appropriate metering valve part number is given in the Parts List, as "Size B':

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