GM Caprice 1990-1993 Repair Guide

Oil Pump

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REMOVAL



  1. Drain and remove the oil pan.
  2.  


CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. Remove the oil pump-to-rear main bearing cap bolt. Remove the pump and the extension shaft.
  2.  
  3. Remove the cotter pin, spring and pressure regulator valve.
  4.  

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

OVERHAUL



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Exploded view of oil pump - Except 5.0L (VIN Y) engine



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Fig. Fig. 2: Measuring gear side clearance

  1. Remove the pump cover attaching screws and the pump cover.
  2.  
  3. Mark gear teeth so they may be reassembled with the same teeth indexing. Remove the idler gear, drive gear and shaft from the pump body.
  4.  
  5. Remove the pressure regulator valve retaining pin, pressure regulator valve and related parts.
  6.  
  7. If the pickup screen and pipe assembly need replacing, mount the pump in a soft-jawed vise and extract the pipe from pump by twisting the assembly as if you are unscrewing the pickup tube from the pump assembly. Do not disturb the pickup screen on the pipe. This is serviced as an assembly.
  8.  
  9. Wash all parts in cleaning solvent and dry with compressed air.
  10.  
  11. Inspect the pump body and cover for cracks or excessive wear. Inspect pump gears for damage or excessive wear.
  12.  

The pump gears and body are not serviced separately. If the pump gears or body are damaged or worn, replacement of the entire oil pump assembly is necessary.

  1. Check the drive gear shaft for looseness in the pump body. Inspect inside of pump cover for wear that would permit oil to leak past the ends of the gears.
  2.  
  3. Inspect the pickup screen and pipe assembly for damage to screen, pipe or relief grommet.
  4.  
  5. Check the pressure regulator valve for fit.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: Measuring oil pump end clearance



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Fig. Fig. 4: Installing the oil pump pickup and screen

  1. If the pickup screen and pipe assembly was removed, it should be replaced with a new part. Loss of press fit condition could result in an air leak and loss of oil pressure. Mount the pump in a soft-jawed vise, apply sealer to end of pipe, and use a suitable tool to tap the pipe in place.
  2.  

Be careful of twisting, shearing or collapsing pipe while installing in pump. Do not use excessive force.

  1. Install the pressure regulator valve and related parts.
  2.  
  3. Install the drive gear and shaft in the pump body.
  4.  
  5. Install the idler gear in the pump body with the smooth side of gear towards pump cover opening.
  6.  

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.

  1. Install the pump cover and torque attaching screws to specifications.
  2.  
  3. Turn drive shaft by hand to check for smooth operation.
  4.  
  5. Install a new shaft extension clip onto the pump drive shaft and snap the extension shaft into the clip, on all except 5.0L (VIN Y) engine.
  6.  

INSTALLATION



  1. Assemble pump and extension shaft to rear main bearing cap. On the 5.0L (VIN Y) engine, ensure the shaft extension washer be 1 / 32 from the tip of the shaft and then insert the washer end of the shaft into the pump and install the pump assembly. On all except the 5.0L (VIN Y) engine, install a new shaft extension with clip onto the pump drive shaft and snap the extension shaft into the clip, then align the slot on top end of extension shaft with drive tang on lower end of distributor drive shaft and install the pump.
  2.  

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. Torque the bolts to specifications:

    4.3L engine: 65 ft. lbs. (88 Nm)
     
    5.0L (VIN E) and 5.7L engines: 77 ft. lbs. (105 Nm)
     
    5.0L (VIN Y) engine: 35 ft. lbs. (47 Nm)
     

  4.  
  5. Install the oil pan and fill the crankcase with engine oil.
  6.  
  7. Start the engine and check the oil pressure.
  8.  

 
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