Oil pressure switch would not shut off fuel pump, however the fuel pump has a secondary route through the oil pressure switch. If the fuel pump relay goes out the pump will then run through the oil pressure switch after the engine gets oil pressure. This results in extended engine cranking time before the engine will start. Have you inspected all fuses, inertia switch (if equipped), relays and wiring before going in for a pump replacement?
To test your oil pressure sending unit, do the following:
Pressure can be tested by temporarily installing an oil pressure gauge in place of the sending unit. Before testing, look up the oil pressure specifications for your vehicle in the appropriate service manual.
Bring the engine up to operating temperature.
Now shut the engine off.
Locate the oil pressure sending unit; usually it is on the lower side of the engine block.
Disconnect the wire from the sending unit and use an open ended wrench to remove the sender. Using pliers can damage the unit.
Tighten the oil pressure test gauge into the hole in the block where the sender was removed.
Check the engine's oil level and fill, if required.
Be extremely careful when working near a running engine. Always wear safety goggles or glasses with side shields when working around moving machinery and be sure that your clothing is not loose.
Now turn the engine on and check the oil pressure on the gauge.
Watch as the engine warms to note any excessive drops due to temperature.
Make sure the engine speed is set to specifications for testing pressure.
If necessary, us a tachometer and adjust the engine idle speed.
Record the measured oil pressure, then turn off the engine.
Compare the test results with the manufacturer's specifications.
If the oil pressure is within specifications, this shows that the oil pressure sending unit may not be working correctly.
In many cases, replacing the oil sending unit will correct the problem.
After the test is complete, reinstall the oil pressure sending unit, start the engine, and confirm there are no leaks.
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Sunday, February 8th, 2009 AT 7:00 PM