Manual - Chapter 5 - Fuel & Oil

10: Fuel pump: examination / renovation

  1. Note that the pump cannot be dismantled for repair or reconditioning; if it is faulty, or stops working, it must be renewed. The only effective test of the pump's condition is described in Section 11 of this Chapter, but this requires the use of a suitable pressure gauge. Ensure that the working area is absolutely clean when servicing the pump.
  2. With the pump removed from the fuel tank, unscrew the nuts which clamp the rubber sleeve to the nylon retaining ring. The retaining ring should have an alignment mark (a small + symbol embossed on it) next to the smaller positive terminal; if none can be seen make your own marks before withdrawing the retaining ring and pulling the pump out of the rubber sleeve and mesh filter. Note that while it is, of course, possible merely to pull the filter off the pump lower end, the filter should be removed and refitted with care so that it is not damaged or distorted.
  3. Disengage the filter from the sleeve, noting the alignment marks. Check the filter for splits or tears; if any are found or if it is a slack fit on the sleeve, the filter must be renewed. If not, swill it in high flash-point solvent to remove any particles of dirt.
  4. Carefully clean all components and check for wear or damage; if any is found the component concerned must be renewed.
  5. Note that the pump has been modified; since the introduction of the 75 models (ie all 1986 on models) a pump is fitted which is manufactured to tighter tolerances to ensure that the delivery rate remains correct even at high operating temperatures. This is now supplied as the replacement part for earlier models also. To prevent the formation of vapour bubbles which would otherwise interrupt the fuel supply, the new pump is fitted with a modified mesh filter and rubber sleeve, the filter being fitted with a separate breather hose.
  6. While the new pump does ensure greater consistency of fuel supply, its tighter tolerances mean that it is more easily damaged by dirt. To prevent this, take great care to ensure that the pump components are kept as clean as possible at all times. Use only lint free cloths for cleaning purposes and flush out the tank immediately if any dirt or water are noticed inside it at any time.
  7. On reassembly, check that all components are absolutely clean, then fit the mesh filter to the rubber sleeve, aligning their marks as shown in the accompanying photograph. Fit the retainer ring to the rubber sleeve and tighten the retaining nuts lightly, the ring will fit only the correct way due to the offset studs and mounting ear cutouts in the rubber sleeve.
  8. Lubricate the pump body with a smear of fuel or a very small amount of engine oil, then press it into the rubber sleeve, taking care not to dislodge the mesh filter, until the locating ribs on the pump body snap into the grooves in the rubber sleeve. If the pump is a very tight fit, remove the retainer ring, press the pump into the rubber sleeve and then refit the ring. When the pump is fully in place, rotate it to align the retainer ring mark with the pump positive (+ ve) terminal and tighten the retainer ring nuts securely. Make a final check that the mesh filter is fully and securely fixed on the rubber sleeve and that the alignment marks are in line.

10.2 Before removing retaining ring check for alignment marks with smaller positive terminal (arrowed)

10.7 Ensure mesh filter is securely fixed on rubber sleeve, with arrows aligned