6. Remove the six bolts and lock washers (if used) which
attach the pump assembly to the engine front cover (Fig. 1) and
withdraw the pump assembly from the cover.
Disassemble Oil Pump
If the oil pump is to be disassembled for inspection or
reconditioning, proceed as follows:
1. Refer to Fig. 5 and remove the two drive screws holding
the pump cover plate to the pump body. Withdraw the over
plate from the pump body.
2. Remove the inner and outer rotors from the pump housing.
Fig. 3 - Measuring Rotor Clearance
Wash all of the parts in clean fuel oil and dry them with compressed air.
The greatest amount of wear in the oil pump is imposed on the lobes of the inner and outer rotors.
This wear may be kept to a minimum by using clean oil. If dirt and sludge are allowed to accumulate in the lubricating
system, excessive rotor wear may occur in a comparatively short period of time.
Inspect the lobes and faces of the pump rotors for scratches or burrs and the surfaces of the pump body and cover plate
for scoring. Scratches or score marks may be removed with an emery stone. Measure the clearance between the inner
and outer rotors at each lobe (Fig. 3). The clearance should not be less than .004" or more than .011 ". Measure the
clearance from the face of the pump body to the side of the inner and outer. rotor with a micrometer depth gage (Fig. 4).
The clearance should be not less than .001 " or more than .0035 ".
Inspect the splines of the inner rotor and the oil pump drive gear. If the splines are excessively worn, replace the parts.
The rotors are serviced as matched sets, therefore, if one rotor needs replacing, replace both rotors.
Remove the oil inlet screen from the oil inlet pipe and clean both the screen and the pipe with fuel oil and dry them with
compressed air. Replace the inlet pipe flange seal ring with a new seal ring if necessary.
Assemble Oil Pump
After the oil pump parts have been cleaned and inspected, refer
to Fig. 5 or 6 and assemble the pump as follows:
1. Lubricate the oil pump outer rotor with engine oil and place it
in the pump body.
2. Lubricate the oil pump inner rotor with engine oil and place it
inside of the outer rotor.
3. Place the cover plate on the pump body and align the drive
screw and bolt holes with the holes in the
Measuring Clearance from Face of Pump
Body to side of Rotor