4.4.1 Cam screw
Position the pump with the advance housing stud uppermost. Fit the cam screw (1) to the cam ring and, using the adaptor tool (2) and a suitable socket (3), tighten the cam screw to the specified torque.
During this operation, the cam ring usually becomes jammed in the housing. Using a hide or rubber mallet, lightly tap the cam screw axially to free the cam ring.
4.4.2 Servo piston
If the advance device is servo-controlled, the servo valve must be fitted to the advance piston before the piston is inserted into the advance housing.
Fit the servo valve (2) through the piston (1) into the inner bore with the longer (reduced diameter) end facing inwards. Fit the spring pin (3) into the valve bore with the tapered end facing outwards. Fit the washer (4) and the internal circlip (5). Ensure that the circlip is properly fitted into its groove in the piston. Fit the piston into the advance housing.
4.4.3 Fitting the advance housing
If not already fitted, fit the advance piston (2) into the advance housing with the closed end of the piston towards the transfer pressure port end of the advance housing.
Using the specified protection sleeve, fit new Orings (5) to the head locating fitting (8) or damper (7) and place the lock-off ball (6) into its recess (if of the non-captive type). Slide the fitting into its hole in the advance housing to retain the lock-off ball.
Put a new gasket (1) onto the advance housing with the straight edge in the central hole closest to the pump housing stud.
Place the advance housing onto the pump housing, engaging the head locating fitting with its thread in the hydraulic head and the cam screw with the advance piston. Ensure that the gasket is correctly located over the housing stud shoulder. Secure the housing with the head locating fitting and a new sealing washer (3) and the dome nut (4). Leave both fixings finger-tight.
4.4.4 Hydraulic head fixings
A) Fitting external valve bodies
Before fitting the O-rings to the valve bodies, fit the bodies through the pump housing and screw them into the hydraulic head to ensure that they are centralised in the holes, and to minimise the risk of damage to the O-rings when the valves are finally fitted into the head. Remove the valve bodies.
(i) Latch valve (if specified)
Reposition the pump with the governor mounting face uppermost. Fit new O-rings (2) and sealing washer (4) to the latch valve body (1). If specified, fit new filter (3). Fit the body through the pump housing to the hydraulic head in the position noted during dismantling, leaving it finger-tight. The internal components will be fitted later.
(ii) Rotor vent switch valve (if specified)
Fit the rotor vent switch valve body (5) with new Orings (3), backing washers (2) and (4). and sealing washer (1). Fit the body through the pump housing to the hydraulic head in the position noted during dismantling, leaving it finger-tight. The internal components will be fitted later.
It is essential that the specified seals are fitted, in their correct order.
(iii) Head locking screw (if specified)
Fit the head locking screw (1) with a new washer and insert it into the head in the position specified, leaving it finger-tight.
Now progressively tighten all head fixings and the advance housing stud cap nut to their specified torque values. Check that the advance piston moves freely in the housing, that the pump still rotates freely and that the latch and rotor vent switch valves move freely in their respective bodies.
B) Assembling the valves
(i) Latch valve
Fit the valve (7) to the body, followed by the spring (6). Fit a new O-ring (5) to the sleeve nut (4), fit the nut into the valve body and tighten the nut to the specified torque. Fit a new seal (3) into the recess in the locknut (2) and screw the adjuster (1) through the locknut. Screw the protruding end of the adjuster into the sleeve nut to the position specified in the Test Plan.
Some pump specifications have "differential" latch valves which are hollow and have a control orifice in the side of the valve stem.
(ii) Rotor vent switch valve
Fit the valve (1) to the body, followed by the spring (2). Fit a new O-ring (3) to the spring plug (4) screw the plug into the body and tighten it to the specified torque.
4.4.5 Advance device fittings (pressure end)
For general fitting instructions for the advance device, refer to section 4.4.3.
A) Manual cold idle advance
Fit a new O-ring (6) to the shaft (7). Apply Shell Alvania R2 grease to the shaft and the O-ring and insert the shaft into the plug (4). Fit a new O-ring (5) to the plug and fit the cam (8) into the plug, to mate with the angled faces of the shaft. Fit the circlip (9) into the internal groove in the plug (4); assemble the plug to the advance housing and tighten it to the specified torque.
Fit the lever (3), spacer (2), and E-clip (1) to the shaft (7) in the position noted during dismantling. The lever position may require altering during setting on the test machine.
B) Temperature-controlled cold idle advance
Fit new O-rings (6) and (7) to the cold advance shaft (5) and fit the shaft to the end cap (8). Fit new O-ring (4) to the end cap; fit new O-ring (2), with backing rings (1) and (3), on either side of O-ring to the end cap. Screw the end cap into the advance housing and tighten it to the specified torque.
Fit the lever (9) loosely to the shaft and the selflocking nut (10). Leave the nut finger tight at this stage, as the lever will be positioned correctly during initial setting.
Later examples of the cold idle advance shaft are supplied as three separate parts i.e. shaft, piston and pin (which is a loose fit in the shaft hole).
C) Pressure end plug
Fit a new O-ring (1) to the plug (2), insert the plug into the advance housing and tighten it to the specified torque.
4.4.6 Advance device fittings (spring end)
A) Automatic start retard and speed advance
Fit the circlip (10) into the groove in the advance housing (8). Fit the retard spring (9), followed by the spring plate (11) with its spigot facing inwards.
Fit the O-ring (4) to the spring cap (3) and place the specified number of shims (5) in the cap, followed by the advance spring(s) (6) and (7). Screw the cap assembly into the advance housing and tighten it to the specified torque. Fit the cap plug (1) with a new washer (2) and assemble it to the cap, finger-tight.
B) Light load advance
Apply Loctite Retainer 601 into the seal recess in the spring cap (6) and insert a new seal (5), with the lip facing inwards, into the cap. Use the special punch to drive the seal squarely into the recess. When correctly fitted, the outer face of the seal housing should be either flush with or slightly recessed in relation to the outer face of the end cap.
Fit a new O-ring (7) to the spring cap.
Fit the circlip (1) to the light load plunger (2) and push the plunger into the spring cap so that the circlip abuts the oil seal. Fit the shims (3) into the light load plunger (the Test Plan for the pump specifies the correct shim thickness), followed by the light load advance spring (4). Screw the end plug assembly into the advance housing (8), making sure that the spring is correctly located. Tighten it to the specified torque.
Press and release the light load plunger several times to confirm that the plunger is fully returned to its outer position by the spring.
C) Speed advance with manual cold idle advance
Assemble the anchor plate (10) to the spring end cap (11), with the single tab on the plate towards the threaded end as shown. Fit the phasing shim (9) with the flat located against the anchor plate tab.
Fit a new O-ring (8) to the spring end cap, against the phasing shim.
Slide the spring piston (1) over the spindle (2) with its cupped end towards the spindle head, followed by the washer (3). Fit new O-rings (4) to the spindle. Fit the spring (5) over the spindle and locate it against the washer.
Refit the same number of shims (7), as noted during dismantling, into the spring cap. In case of doubt, the Test Plan for the pump will specify the thickness of shims to be fitted.
Fit the advance spring (6) against the shims and insert the spindle assembly through the spring cap assembly.
Fit the retard spring (3) into the advance piston (1) and screw the spring end cap (4) complete with the plunger and spring assembly into the advance housing (2). When correctly fitted, the tab on the anchor plate must be positioned against the machined flat on the advance housing. Tighten the end cap to the specified torque.
Pack the ball recesses in the manual idling advance lever (5) with Shell Alvania R2 grease and fit the three steel balls (4).
Assemble the detent plate (3) with the flat side towards the spring cap (2), and engage the lug on the detent plate between the long and short legs on the anchor plate (1).
With the three steel balls held captive by the grease, fit the idling advance lever so that the balls engage with the recesses in the detent plate. Screw on the adjuster nut (6) until approximately six threads of the spindle are left exposed. Hold the adjuster nut with a suitable spanner; fit the locknut (7) and tighten it to the specified torque.
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