GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Oil Pump

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REMOVAL & INSTALLATION



See Figure 1

In Line 6-Cylinder
  1. Remove the oil pan as described earlier in this section.
  2.  
  3. Remove the two flange mounting bolts along with the pick-up bolt, then remove the pump and screen together.
  4.  

To install:
  1. Align the oil pump driveshafts to match with the distributor tang and position the flange over the distributor lower bushing.
  2.  
  3. Support the pump in this position, then install and tighten the pump mounting bolts.
  4.  
  5. Install the oil pan to the engine block.
  6.  

Gasoline and Diesel V6 and V8 (Except 231 V6)
  1. Remove the oil pan as described earlier in this section.
  2.  
  3. Remove the pump-to-rear main bearing cap bolts and remove the pump and extension shaft.
  4.  

To install:
  1. Align the slot on the top end of the extension shaft with the drive tang on the lower end of the distributor driveshaft (or until the shaft mates into the oil pump drive gear on diesels) and install the rear main bearing cap bolts.
  2.  
  3. Position the pump screen so that the bottom edge is parallel to the oil pan rails.
  4.  
  5. Install the oil pan to the engine block.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: Typical oil pump installation-V6 diesel engine shown

231 V6

The oil pump is located in the timing chain cover and is connected by a drilled passage to the oil screen housing and pipe assembly in the oil pan. All oil is discharged from the pump to the oil pump cover assembly, on which the oil filter is mounted.

  1. For access to the oil pump cover and gears, first remove the oil filter.
  2.  
  3. Remove the screws which attach the oil pump cover assembly to the timing chain cover.
  4.  
  5. Remove the cover assembly and slide out the oil pump gears. Clean the gears and inspect them for any obvious defects such as chipping or scoring.
  6.  
  7. Remove the oil pressure relief valve cap, spring and valve. Clean them and inspect them for wear or scoring. Check the relief valve spring to see that it is not worn on its side or collapsed. Replace the spring if it seems questionable.
  8.  
  9. Check the relief valve for a correct fit in its bore. It should be an easy slip fit and no more. If any perceptible shake can be felt, the valve and/or cover should be replaced.
  10.  

To install:
  1. Lubricate the pressure relief valve and spring and place them in the cover. Install the cap and the gasket. Torque the cap to 35 ft. lbs. (47 Nm).
  2.  
  3. Pack the oil pump gear cavity full of petroleum jelly. Do not use gear lube. Reinstall the oil pump gears so that the petroleum jelly is forced into every cavity of the gear pocket, and between the gear teeth. There must be no air spaces. This step is very important. Unless the pump is packed, it may not begin to pump oil as soon as the engine is started.
  4.  
  5. Install the cover assembly using a new gasket and sealer. Tighten the screws to 10 ft. lbs. (14 Nm).
  6.  
  7. Install the oil filter.
  8.  

INSPECTION & OVERHAUL



See Figures 2, 3 and 4

231 V6 Engine

The oil pump is located in the timing chain cover and is connected by a drilled passage to the oil screen housing and pipe assembly in the oil pan. All oil is discharged from the pump to the oil pump cover assembly, on which the oil filter is mounted.

  1. For access to the oil pump cover and gears, first remove the oil filter.
  2.  
  3. Remove the screws which attach the oil pump cover assembly to the timing chain cover.
  4.  
  5. Remove the cover assembly and slide out the oil pump gears. Clean the gears and inspect them for any obvious defects such as chipping or scoring.
  6.  
  7. Remove the oil pressure relief valve cap, spring and valve. Clean them and inspect them for wear or scoring. Check the relief valve spring to see that it is not worn on its side or collapsed. Replace the spring if it seems questionable.
  8.  
  9. Check the relief valve for a correct fit in its bore. It should be an easy slip fit and no more. If any perceptible shake can be felt the valve and/or the cover should be replaced.
  10.  
  11. Install the oil pump gears (if removed) and the shaft in the oil pump body section of the timing chain cover to check the gear end clearance and gear side clearance. Check gear end clearance by placing a straight edge over the gears and measure the clearance between the straight edge and the gasket surface. Clearance should be between 0.002-0.006 in. Check gear side clearance by inserting the feeler gauge between the gear teeth and the side wall of the pump body. Clearance should be between 0.002-0.005 in.
  12.  
  13. Check the pump cover flatness by placing a straight edge across the cover face, with the feeler gauge between the straight edge and the cover. If clearance is 0.001 in. or more, replace the cover.
  14.  
  15. To install, lubricate the pressure relief valve and spring and place them in the cover. Install the cap and the gasket. Torque the cap to 35 ft. lbs. (47 Nm).
  16.  
  17. Pack the oil pump gear cavity full of petroleum jelly. Do not use gear lube. Reinstall the oil pump gears so that the petroleum jelly is forced into every cavity of the gear pocket, and between the gear teeth. There must be no air spaces. This step is very important.
  18.  


WARNING
Unless the pump is primed this way, it may not produce any oil pressure when the engine is started.

  1. Install the cover assembly using a new gasket and sealer. Tighten the screws to 10 ft. lbs. (14 Nm).
  2.  
  3. Install the oil filter.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: Exploded view of a common oil pump assembly



Click image to see an enlarged view

Fig. Fig. 3: Checking oil pump gear end clearance



Click image to see an enlarged view

Fig. Fig. 4: Checking oil pump gear side clearance

Gasoline and Diesel V6 and V8 (Except 231 V6)
  1. Remove the oil pump drive shaft extension.
  2.  
  3. Remove the cotter pin, spring and the pressure regulator valve.
  4.  

Place your thumb over the regulator bore before removing the cotter pin, as the spring is under pressure.

  1. Remove the oil pump cover attaching screws and remove the oil pump cover and gasket. Clean the pump in solvent or kerosene, and wash out the pick-up screen.
  2.  
  3. Remove the drive gear and idler gear from the pump body.
  4.  
  5. Check the gears for scoring and other damage. Install the gears if in good condition, or replace them if damaged. Check gear end clearance by placing a straight edge over the gears and measure the clearance between the straight edge and the gasket surface with a feeler gauge. End clearance for both diesels is 0.0005-0.0075 in. and other V8s is 0.002-0.0065 in. If end clearance is excessive, check for scores in the cover that would bring the total clearance over specification.
  6.  
  7. Check gear side clearance by inserting the feeler gauge between the gear teeth and the side wall of the pump body. Clearance should be between 0.002-0.005 in.
  8.  
  9. Pack the inside of the pump completely with petroleum jelly. DO NOT use engine oil The pump MUST be primed this way or it may not produce any oil pressure when the engine is started.
  10.  
  11. Install the cover screws and tighten alternately and evenly to 8 ft. lbs. (11 Nm).
  12.  
  13. Position the pressure regulator valve into the pump cover, closed end first, then install the spring and retaining pin.
  14.  

When assembling the driveshaft extension to the drive shaft, the end of the extension nearest the washers must be inserted into the drive shaft.

  1. Insert the driveshaft extension through the opening in the main bearing cap and block until the shaft mates into the distributor drive gear.
  2.  
  3. Install the pump onto the rear main bearing cap and install the attaching bolts. Torque the bolts to 35 ft. lbs. (47 Nm).
  4.  
  5. Install the oil pan to the engine block.
  6.  

 
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