Repair Pontiac Mid-size 1974-1983 Repair Guide

Oil Pump

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REMOVAL & INSTALLATION



The oil pump is mounted to the bottom of the block and is accessible only by removing the oil pan.

On all engines, including diesel, remove the oil pan, then unbolt and remove the oil pump and screen as an assembly. On the 151 four and 250 six, remove the flange mounting bolts and nut from the elongated number 6 main bearing cap bolt, then remove the pump.

To install, align the oil pump drive shaft on 151 four 250 six cylinder engines to match with the distributor tang and position the pump flange over the distributor lower bushing. Install the pump mounting bolts. On V8 engines, insert the drive shaft extension through the opening in the main bearing cap until the shaft mates with the distributor drive gear. You may have to turn the drive shaft extension one way or the other to get the two to mesh. Position the pump on the cap and install the attaching bolts. Install the oil pans on all engines.

OVERHAUL





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Fig. Fig. 1 Exploded view of a typical oil pump



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Fig. Fig. 2 Use feeler gauges to measure the oil pump side clearance

151 Four and 250 Inline Six Cylinder Engines
  1. With the pump removed from the block, remove the 4 cover attaching screws, the cover, idler gear and drive gear and shaft.
  2.  
  3. Remove the pressure regulator valve and related valve parts.
  4.  


WARNING
Do not disturb the oil pickup pipe on the screen or body.

  1. Inspect the pump body for excessive wear or cracks, and inspect the pump gears for excessive wear, cracks or damage. Check the shaft for looseness in the housing; it should not be a sloppy fit. Check the inside of the cover for wear that would permit oil to leak past the ends of the gears. Remove any debris from the surface of the screen, and check the screen for damage. Check the pressure regulator valve plunger for fit in the pump body.
  2.  
  3. Assemble the pump as previously described. When tightening the cover screws (6 ft. lbs. on the 250 six, 8 ft. lbs. On the 151 four), check to make sure the shaft turns freely.
  4.  

V6 Engines

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. To remove 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 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 .002 in. and .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 .002 in. and .005 in.
  12.  
  13. Check the pump cover flatness by placing a straight edge across the cover face, with a feeler gauge between the straight edge and the cover. If clearance is .002 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. Tighten the cap to 35 ft. lbs.
  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 won't 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.
  2.  
  3. Install the oil filter.
  4.  

V8 Engines (Including Diesel)
  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 pressure 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 the diesel is .0005 in. to .0075 in.; 350 (R) and 403 (K) is .0015 in. to .0085 in.; and other V8s is .002 in. to .0065 in. If end clearance is excessive, check for scores in the cover that would bring the total clearance over the specs.
  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 .002 in. and .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 won't produce any oil pressure when the engine is started.
  10.  
  11. Install the cover screws and tighten alternately and evenly to 8 ft. lbs.
  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 drive shaft extension to the drive shaft, the end of the extension nearest the washers must be inserted into the drive shaft.

  1. Insert the drive shaft 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. Tighten the bolts to 35 ft. lbs.
  4.  
  5. Install the oil pan.
  6.  

 
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