TESTING SPARK PLUGS
Start by disconnecting each spark plug wire on your engine one at a time while the engine is running. If the engine drops speed or starts running rough when one is disconnected, you know that spark plug is good. If you disconnect a spark plug and no significant change happens in the engine, you have found a bad spark plug.
Test the spark plug ignition by disconnecting the spark plug wire from the spark plug. Hold the end of the spark plug wire close to a metal surface. If the spark plug is good, you will see a spark or you'll hear a crackling noise. This means that voltage is getting through the wire to the spark plug.
See if there is a spark on each one of your spark plug wires when the engine is cranked. If compression is good, you will have spark on each one of your spark plug cylinders. No spark would mean that a spark plug wire is dead.
Remember that each link connected to your spark plugs needs to be hooked up securely. Links include battery cable, ignition wires and coil wires, not just the spark plug wires.
Wiggle the link connections from your spark plugs. Then test again. Sometimes it's just a matter of a line connection being loose.
Check to make sure that the end of each of the spark plugs is clean and free of any dirt, oil or grease deposits. Sometimes you can just clean them thoroughly and they'll pass the test. But if they still don't test well after cleaning, you'll need to replace them.
CHECKING FUEL PRESSURE
Locate the fuel pressure test port, you may have to refer to service information to locate this port or you may have to T into the fuel supply line.
Cycle the ignition key "on" and check your readings, write this number down. Start the car and run it, record your fuel pressure reading again. If your performance problem occurs when driving then you will need to take a road test to record the fuel pressure when driving. Tape the gauge to the windshield and have an assistant watch the gauge while you drive.
Compare your reading with specifications for your car, if it is low then I would start by replacing the fuel filter and retest. If there is no pressure then the pump may be at fault. Perform electrical tests on pump before replacing it.
Make sure everything is back together and no fuel leaks are present.
Thursday, November 25th, 2010 AT 3:31 AM