Sorry I'm not familiar with the V-6 engine in your model but I'm very familiar with the 4 cylinder. The systems are nearly identical in operation so I'll share a few important details.
The crankshaft position sensor (ckp) and camshaft position sensor (cmp) send very accurately timed pulses to the engine computer when the engine is rotating, (cranking or running). The pulses are the starting point for the computer to determine when to fire a spark plug and fuel injector. Data from other sensors fine tunes the spark and injector timing for lowest tail pipe emissions.
There is one other real important fact you will want to know about this system. When you turn on the ignition switch, you might be able to hear the fuel pump run, but it will only run for about two seconds, then it will turn off. The power for the fuel pump comes from the Automatic Shutdown (ASD) relay which is turned on by the engine computer. Fuel pressure in the system should easily be maintained for weeks without running the engine, but in case it leaks down internally a little, that two-second burst from the fuel pump insures pressure is up and ready for starting.
When the engine is being cranked, (or it's running), the engine computer knows it due to the pulses arriving from the two position sensors. That's when the computer turns on the ASD relay again. Besides the fuel pump, that relay sends power to the ignition coil, (spark plugs), fuel injectors, alternator, and oxygen sensor heaters. These things don't need power until the engine is running so turning them on this way reduces battery drain.
More importantly, in the event of a crash that ruptures a fuel line, raw fuel would be pumped onto the ground and be a serious fire hazard. With the loss of fuel pressure, no fuel will spray from the injectors so the engine will stall. No pules will come from the cam and crank position sensors so the engine computer turns the ASD relay off. This removes power from the fuel pump, therefore, no fuel is pumped onto the ground. This part of the circuit is extremely reliable and easy to diagnose. It's WAY more effective than Ford's silly, aggravating "inertia switch" which does not respond to a ruptured fuel line. Even if the engine stalls on a Ford, the fuel pump could keep running. And, driving over a pothole or curb could trip the inertia switch and leave you sitting on the side of the road. Chrysler's system is much more effective and safe.
On the four cylinder engines, there has been a lot of trouble with the camshaft position sensors. It will cause a no-start condition and can cause engine stalling intermittently. It is common for it to cool down after a half hour, and allow the engine to start again. The original design that first showed up in 1995 is no longer available. The new design comes with a new electrical connector that must be spliced into the wiring harness.
Caradiodoc
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Friday, January 8th, 2010 AT 3:14 AM
