Oil Pressure Diagnosis and Testing

Oil Pressure Diagnosis and Testing

Low or No Oil Pressure

The following conditions may cause low or no oil pressure:

* Low oil level-Fill to the full mark on the oil level indicator.
* Incorrect or malfunctioning oil pressure switch-Replace the oil pressure switch.
* Incorrect or malfunctioning oil pressure gage-Replace the oil pressure gage.
* Improper oil viscosity or diluted oil

- Install oil of proper viscosity for expected temperature.
- Install new oil if the oil is diluted.

* A worn or dirty oil pump-Clean or replace the oil pump.
* A plugged oil filter-Replace the oil filter.
* A loose or plugged oil pickup screen-Replace the oil pickup screen.
* A hole in the oil pickup tube-Replace the oil pickup tube.
* Excessive rod, main, or cam bearing clearance-Replace the bearings.
* Cracked, porous, or plugged oil gallery-Repair or replace the engine block.
* Missing or improperly installed gallery plugs-Install or repair the plugs as needed.
* A stuck pressure regulator valve

- Inspect the pressure regulator valve for sticking in the bore.
- Inspect the bore for scoring and burrs.

* A worn or poorly machined camshaft-Replace the camshaft.
* Worn valve guides-Repair the valve guides as needed.

Oil Pressure Testing

Tools Required
* J-21867-6 Oil Pressure Adapter Fitting
* J 25087-C Oil Pressure Tester and Pump Primer

If the vehicle has low oil pressure complete the following steps:

1. Inspect the oil level.
2. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle (Service and Repair).
3. Remove the oil filter.
4. Assemble the plunger valve in the large hole of the J 25087-C base. Insert the hose in the small hole of the J 25087-C base. Connect the gage to the end of the hose.
5. Insert the flat side of the rubber plug in the bypass valve without depressing the bypass valve.
6. Install the J 25087-C andJ-21867-6 on the filter mounting pad.
7. Start the engine.
8. Inspect the overall oil pressure, the oil pressure switch, and for noisy lifters. Ensure that the engine is at operating temperature before inspecting the oil pressure. Refer to Engine Mechanical Specifications (Specifications) for proper oil pressure specifications.
9. If adequate oil pressure is indicated, test the oil pressure switch.
10. If a low reading is indicated, press the valve on the tester base in order to isolate the oil pump and/or its components from the lubricating system. An adequate reading at this time indicates a good pump and the previous low pressure was due to worn bearings, etc. A low reading while pressing the valve indicates a faulty pump.