3406E and 3456 Industrial Engines Testing and Adjusting – Engine Oil Pressure – Test

5. The results must fall within the “ACCEPTABLE” range on the chart.A problem exists when the results fall within the “NOT ACCEPTABLE” range on the chart. This problem needs to be corrected. Engine failure or a reduction in engine life can be the result if engine operation is continued with oil manifold pressure outside this range.

   Note: A record of engine oil pressure can be used as an indication of possible engine problems or damage. A possible problem could exist if the oil pressure suddenly increases or decreases 70 kPa (10 psi) and the oil pressure is in the “ACCEPTABLE” range. The engine should be inspected and the problem should be corrected.

6. Compare the engine oil pressure from Step 3 with the other oil pressure indicators that are for the engine.

7. An engine oil pressure indicator that has a defect or an engine oil pressure sensor that has a defect can give a false indication of a low oil pressure or a high oil pressure. If there is a notable difference between the engine oil pressure readings make necessary repairs.

8. If a low engine oil pressure condition is confirmed, refer to “Reasons for Low Engine Oil Pressure”.

9. If engine oil pressure is above the specification, refer to “Reason for High Engine Oil Pressure”.

Reasons for Low Engine Oil Pressure

• Oil level is low. Refer to Step 1. 
• Oil is contaminated. Refer to Step 2. 
• Engine oil bypass valves are open. Refer to Step 3. 
• The lubrication system is open. Refer to Step 4. 
• The oil suction tube has a leak or a restricted inlet screen. Refer to Step 5. 
• The engine oil pump is faulty. Refer to Step 6. 
• Engine bearings have excessive clearance. Refer to Step 7. 

1. Check the engine oil level in the crankcase. If the oil level is below the oil pump’s supply tube, the oil pump will not have the ability to supply enough lubrication to the engine components. If the engine oil level is low, add engine oil in order to obtain the correct engine oil level. Refer to Operation and Maintenance Manual, “Engine Oil Level – Check” for information that is related to checking the engine oil.

2. Engine oil that is contaminated with fuel or coolant will cause low engine oil pressure. High engine oil level in the crankcase can be an indication of contamination. Determine the reason for contamination of the engine oil and make the necessary repairs. Replace the engine oil with the approved grade of engine oil. Also replace the engine oil filter. Refer to Operation and Maintenance Manual, “Engine Oil and Filter – Change” for information that is related to replacing the engine oil and the filter.

3. If the engine oil bypass valves are held in the open position, a reduction in the oil pressure can be the result. This may be due to debris in the engine oil. If the engine oil bypass valves are stuck in the open position, remove each engine oil bypass valve and clean each bypass valve in order to correct this problem. You must also clean each bypass valve bore. Install new engine oil filters. For information on the repair of the engine oil bypass valves, refer to Disassembly and Assembly, “Engine Oil Filter Base – Disassemble”.

4. An oil line or an oil passage that is open, broken, or disconnected will cause low engine oil pressure. An open lubrication system could be caused by a piston cooling jet that is missing or damaged.Note: The piston cooling jets direct engine oil toward the bottom of the piston in order to cool the piston. This also provides lubrication for the piston pin. Breakage, a restriction, or incorrect installation of the piston cooling jets will cause seizure of the piston.

5. The inlet screen of the oil suction tube for the engine oil pump can have a restriction. This restriction will cause cavitation and a loss of engine oil pressure. Check the inlet screen on the oil pickup tube and remove any material that may be restricting engine oil flow. Low engine oil pressure may also be the result of the oil pickup tube that is drawing in air. Check the joints of the oil pickup tube for cracks or a damaged O-ring seal. Remove the engine oil pan in order to gain access to the oil pickup tube and the oil screen. Refer to Disassembly and Assembly, “Engine Oil Pan – Remove and Install” for more information.

6. Check the following problems that may occur to the engine oil pump. 
   1. Air leakage in the supply side of the oil pump will also cause cavitation and loss of oil pressure. Check the supply side of the oil pump and make necessary repairs. For information on the repair of the engine oil pump, refer to Disassembly and Assembly, “Engine Oil Pump – Remove”.

    

   2. Oil pump gears that have too much wear will cause a reduction in oil pressure. Repair the engine oil pump. For information on the repair of the engine oil pump, refer to Disassembly and Assembly, “Engine Oil Pump – Remove”.

7. Excessive clearance at engine bearings will cause low engine oil pressure. Check the engine components that have excessive bearing clearance and make the necessary repairs.

Reason for High Engine Oil Pressure