4.1 Oil Pump
DETROIT DIESEL 53
1. Refer to Fig. 5 or 6 and remove the two drive screws
holding the pump cover plate to the pump body.
Withdraw the cover plate from the pump body.
2. Remove the inner and outer rotors from the pump
Wash all of the parts in clean fuel oil and dry them with
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
Fig. 3. Measuring Rotor Clearance
and cover plate for scoring. Scratches or score marks
may be removed with an emery stone.
Remove the six bolts and lock washers (if used)
which attach the pump assembly to the engine front
Measure the clearance between the inner and outer
cover (Fig. 1) and withdraw the pump assembly from
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
Disassemble Oil Pump
the inner and outer rotor with a micrometer depth gage
If the oil pump is to be disassembled for inspection or
(Fig. 4). The clearance should be not less than .001 "
reconditioning, proceed as follows:
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
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 and assemble the pump as
1. Lubricate the oil pump outer rotor with engine oil and
place it in the pump body.
Fig. 4.- Measuring Clearance from Face of Pump Body
2. Lubricate the oil pump inner rotor with engine oil and
to Side of Rotor
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.
1972 General Motors Corp.