Oil Pump: Service and Repair

Fig. 24 Oil pump exploded view. 6-225 (3.7L):

Engine lubrication. 6-225 (3.7L) (Typical):

6-225 (3.7L)

Remove pump from side of engine by first unbolting oil pump cover. Outer rotor will drop out when cover is removed. Do not allow rotor to be damaged by dropping it. Oil pump can now be unbolted and disassembled for inspection. Press off drive gear, supporting gear to keep load off aluminum body. Inner rotor and shaft can now be removed. Remove oil pressure relief valve plug and lift out spring and plunger. Clean all parts thoroughly. If mating surface of oil pump cover is scratched or grooved, replace pump assembly.

Fig. 25 Checking oil pump cover flatness. Typical:

Lay a straightedge across pump cover surface. If a 0.0015 inch feeler gauge can be inserted between cover and straightedge, replace pump assembly.

Fig. 26 Measuring outer rotor thickness:

If outer rotor thickness measures 0.649 inch on 1980 or 0.825 inch or less on 1981-87 engines, and the diameter is 2.469 inches or less, replace shaft and both rotors.

Fig. 27 Measuring inner rotor thickness:

Shaft and both rotors should also be replaced if inner rotor thickness measures 0.649 inch or less on 1980, or 0.825 or less on 1981-87 engines.

Fig. 28 Measuring outer rotor clearance in pump body:

With outer rotor inserted into pump body, press rotor to one side with fingers. If clearance between rotor and pump body is 0.014 inch or more, replace oil pump assembly.

Fig. 29 Measuring clearance over rotor:

With inner rotor inserted into pump body, place a straightedge across face between bolt holes. If a feeler gauge of 0.004 inch or more can be inserted between rotors and straightedge, replace oil pump assembly.

Fig. 30 Measuring clearance between rotors:

Shaft and both rotors should be replaced if tip clearance between inner and outer rotor exceeds 0.010 inch. Inspect oil pressure relief valve plunger for scoring and free operation in its bore. The relief valve spring has a free length of 2-1/4 inches and should test between 22.3 and 23.3 lbs. when compressed to 1-19/32 inch. Replace spring that fails to meet specifications.

Using new parts as required, assemble pump except for outer rotor and cover. Install oil pump on engine then coat inside of pump with oil to assure priming. Install outer rotor and cover using new seal ring.