Ford Mustang 1989-1993 Repair Guide

Oil Pump



See Figures 1 and 2

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Fig. Fig. 1: Oil pump mounting-2.3L engine

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Fig. Fig. 2: Oil pump mounting-5.0L engine

On most of the engines covered by this information (except for the early model 2.3L engines), the oil pump and pickup tube assembly must be unbolted and positioned in the oil pan, in order to remove the pan while the engine is installed in the vehicle.

  1. Disconnect the negative battery cable for safety.
  3. Remove the oil pan, along with the oil pump and pickup tube assembly on all but early model 2.3L engines.
  5. If not done for pan removal, loosen the retainers, then remove the oil pump pickup (inlet) tube and screen assembly, along with the oil pump assembly.

To install:
  1. Prime the oil pump by filling either the inlet or outlet ports with engine oil and rotating the pump shaft to distribute the oil within the pump body.
  3. Position the intermediate driveshaft into the distributor socket. With the shaft firmly seated in the distributor socket, the stop on the shaft should touch the roof of the crankcase. Remove the shaft and position the stop, as necessary.

Remember, that on most vehicles covered by this information, you will have to position the oil pan over the crossmember (with the pump in the pan), then raise the pump into position and install.

  1. Position a new gasket on the pump body, insert the intermediate shaft into the oil pump and install the pump and shaft as an assembly.

Do not attempt to force the pump or shaft into position if it will not seat readily. The driveshaft hex may be misaligned with the distributor shaft. To align, rotate the intermediate shaft into a new position.

  1. Tighten the oil pump attaching screws to 14-21 ft. lbs. (19-29 Nm) on the 2.3L engine and 22-32 ft. lbs. (30-43 Nm) on the 5.0L engine.
  3. If separated, clean and install the oil pump inlet tube and screen assembly.
  5. Install the oil pan.
  7. Connect the negative battery cable.


See Figures 3 and 4

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Fig. Fig. 3: Check the inner-to-outer rotor tip clearance using a feeler gauge

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Fig. Fig. 4: Check rotor vertical clearance (end-play) using a straightedge and a feeler gauge

  1. Wash all parts in solvent and dry them thoroughly with compressed air. Use a brush to clean the inside of the pump housing and the pressure relief valve chamber. Be sure all dirt and metal particles are removed.
  3. Check the inside of the pump housing and the inner and outer gears for damage or excessive wear.
  5. Check the mating surface of the pump cover for wear. Minor scuff marks are normal, but if the cover, gears or housing surfaces are excessively worn, scored or grooved, replace the pump. Inspect the rotor for nicks, burrs or score marks. Remove minor imperfections with an oil stone.
  7. Measure the inner-to-outer rotor tip clearance. With the rotor assembly removed from the pump and resting on a flat surface, the inner and outer rotor tip clearance must not exceed 0.012 in. (0.30mm) with the feeler gauge inserted 0.5 in. (13mm) minimum.
  9. With the rotor assembly installed in the housing, place a straightedge over the rotor assembly and the housing. Measure the rotor end-play between the straightedge and both the inner and outer race. The maximum clearance must not exceed 0.005 in. (0.13mm).
  11. Inspect the relief valve spring to see if it is collapsed or worn. Check the relief valve spring tension. Specifications are as follows:

    2.3L engine - 12.6-14.5 lbs. @ 1.20 in.
    5.0L engine - 10.6-12.2 lbs. @ 1.704 in.

  13. If the spring tension is not within specification and/or the spring is worn or damaged, replace the pump.
  15. Check the relief valve piston for scores and free operation in the bore.
  17. Check the driveshaft-to-housing bearing clearance by measuring the OD of the shaft and the ID of the housing bearing. Clearance should be 0.0015-0.0030 in. (0.038-0.076mm).

Internal oil pump components are not serviced. If any component is out of specification, the entire pump must be replaced.