Got it. Let's clear up some misconceptions. I can't think of an instance where there has been a defective fuel pressure regulator on a Chrysler product. GM has a ton of trouble with them leaking raw fuel into the vacuum hose, but not Chrysler.
I can't remember if the Neon uses a separate fuel pump relay, but regardless, if you don't have voltage to the dark green / orange wire in the coil pack, you don't have fuel pressure either. With a separate fuel pump relay, it is turned on along with the automatic shutdown (ASD) relay. Some models only use the automatic shutdown relay. In that case it runs the fuel pump along with the coil pack, injectors, and alternator.
Here's where it gets misleading. Use your test light or voltmeter to measure the voltage on the dark green / orange wire in the coil pack or on any of the injectors. You WILL see voltage there for just one second as soon as you turn on the ignition switch, then it will go away. You will likely hear the hum of the fuel pump too for that one second. That's where the apparent fuel pressure is coming from. If you don't have voltage for that one second, we gotta go in a different direction.
What you will most likely find next is that voltage does not come back during engine cranking. That's why there is no spark and the fuel pump will not be running. The Engine Computer has not turned the ASD relay back on in response to engine rotation. To clarify what I'm trying to say, you must test for voltage on the dark green / orange wire while cranking the engine. The computer turns on the ASD relay when it sees engine rotation, (cranking or running).
When the computer doesn't turn the ASD relay on during cranking, it is because of a lack of pulses from the crankshaft position sensor or the camshaft position sensor. Most of the problems are caused by the camshaft sensor. The Check Engine light should also be on and there will be a diagnostic fault code stored in the computer's memory related to which sensor isn't working. If you get a code related to "cam and crank sync", the computer has shut the engine down to protect the valves due to a jumped timing belt. If the timing marks look like they're lined up correctly, pull the cam sprocket off and check for a sheared off dowel pin. That only pertains to the single overhead cam engine.
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Wednesday, December 15th, 2010 AT 12:33 AM