Oil Pump: Service and Repair

REMOVAL

1. Remove oil pan, refer to OIL PAN procedure.
2. Remove pump to rear main bearing attaching bolt, then the pump and extension shaft.

Fig. 10 Oil Pump Assembly:

DISASSEMBLE

1. Remove pump cover attaching bolts (7), Fig. 10, and pump cover (3). Mark gear teeth to ensure correct position during assembly.
2. Remove idler gear and drive gear (2), then the shaft from pump body (1).
3. Remove pressure regulator valve retaining pin (6), pressure regulator spring (5) and valve (4).
4. If pickup screen and pipe assembly need to be replaced, mount pump in a suitable vise, then remove pipe from pump cover. Do not remove pickup screen from pipe. This is serviced as an assembly.

Fig. 11 Measuring Oil Pump Gear Lash:

Fig. 12 Measuring Gear Side Clearance:

Fig. 13 Measuring Oil Pump Gear Pocket:

Fig. 14 Measuring Oil Pump End Clearance:

CLEANING & INSPECTION

1. Wash all parts in suitable cleaning solvent, then dry with compressed air.
2. Inspect pump body and cover for cracks or excessive wear.
3. Inspect pump gears for damage or excessive wear. Pump gears and body are not serviced separately. If pump gears are defective, replace entire oil pump assembly.
4. Check drive gear shaft for looseness in the pump body.
5. Inspect inside of pump cover for wear that would permit oil to leak past ends of gears.
6. Inspect pickup screen and pipe assembly for looseness or damage.
7. Check pressure regulator valve for damage and proper fit.
8. Using a straightedge and feeler gauge, check clearances as shown in Figs. 11 through 14.
9. Install gears and measure in several places, on 1989 models, gear lash should be within .009-.015 inch, on 1990-92 models, gear lash should be within .0037-.0077 inch.
10. On all models, measure depth and diameter of oil pump gear pocket, on 1989 models, depth should be 1.195-1.198 inch and diameter should be 1.498-1.50 inch. On 1990-92 models, depth should be 1.202-1.205 inch and diameter should be 1.504-1.506 inch.
11. On all models, measure gear side clearance, gear side clearance should be .003-.004 inch.
12. Measure gear end clearance, on 1989 models, gear end clearance should be .002-.005 inch and on 1990-92 models, gear and clearance should be .002-.006 inch. When determining pump service ability based on end clearance, consider depth of wear pattern in pump cover.

ASSEMBLY

1. Lubricate all internal parts with engine oil during assembly.
2. Install pump gears.
3. Prime engine oil galleries by removing engine oil pump drive unit and rotate oil pump using suitable drill motor, socket and extension.
4. Install oil pump cover and gasket.
5. Install pressure regulator valve and spring, then install cotter pin or plug, if equipped.
6. If pipe assembly was removed, it should be replaced with a new part. Mount pump in suitable vise and apply suitable sealer to outside diameter of swagged end of pipe, then tap pipe in place using a suitable tool. Loss of press fit condition could result in an air leak and loss of oil pressure. Also use caution not to twist, shear or collapse pipe during installation.
7. Turn driveshaft by hand to ensure smooth operation.

INSTALLATION

1. Install pump and extension shaft with retainer to rear main bearing cap, aligning top end of hexagon extension shaft with hexagon socket of distributor drive gear.
2. Install pump to rear bearing cap bolt and torque to specifications.
3. Install oil pan, refer to OIL PAN procedure.