Oil Pump: Service and Repair

Fig. 31 Oil pump. V8-318 (5.2L) & V8-360 (5.9L):

Engine lubrication. V8-318 (5.2L) & V8-360 (5.9L) (Typical):

V8-318 (5.2L) & V8-360 (5.9L)

Removal of oil pump for servicing requires oil pan to be removed and oil pump unbolted from rear main bearing cap. With pump removed, disassemble pressure relief valve by pulling out cotter pins and drilling a 1/8 inch hole into center of relief valve retainer cap. Insert a self-threading sheet metal screw into cap and secure head in vise. While supporting pump body, remove cap by tapping body with soft hammer. Discard retainer cap and remove spring and relief valve. Relief valve spring has a free length of 2-1/32 to 2-3/64 inch and should test between 16.2 and 17.2 lbs. when compressed to 1-11/32 inch. Replace spring that fails to meet specifications. Unbolt oil pump cover and discard oil seal ring. Inner rotor and shaft can now be removed as well as outer rotor. Clean all parts thoroughly and inspect for damage or wear. 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 .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 0.825 inch or less on 318 engine, or less than 0.943 inch on 360 engine, or the diameter is 2.469 inches or less, replace the outer rotor.

Fig. 27 Measuring inner rotor thickness:

If inner rotor measures 0.825 inch or less on 318 engine or less than 0.943 on 360 engine, replace inner rotor and shaft assembly.

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 .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 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. Using new parts as required, assemble pump. Prime pump before installation by filling rotor cavity with engine oil.

Fig. 32 Oil pump. V8-446 (7.3L):

Fig. 33 Measuring oil pump gear to body clearance. V8-446 (7.3L):

V8-446 (7.3L)

The oil pump consists of two gears and a pressure relief valve enclosed in the body. The pump is driven from the distributor drive gear. The body is equipped with a regulator valve that limits oil pressure to approximately 50 psi.

After removing the oil pan, the pump may be removed from its mounting and disassembled for repairs. With the pump cover removed, exert pressure against gear with the thumb so as to push gear from outlet side of pump. Measure clearance between outside diameter of gear and bore of housing. If clearance is not between 0.0014 - 0.0054 inch, replace worn parts. Check pump shaft clearance in bore. If clearance is not between 0.001 - 0.0025 inch, replace pump. Check backlash between pump body and gears. If clearance is more than 0.0107 inch, replace gear. Check body gear end clearance. Clearance should be 0.0015 - 0.0065 inch. If endplay is not within specifications, add or remove oil pump cover gaskets to obtain specified clearance.