QuestionQUESTION: My son's 1994 Chrysler T&C 3.8L van was not starting well and would sometimes die intermittently. Harder to start when warm then cold. After several attempts turning the key from off to on the engine would finally start. After trying other things I had the idea that the camshaft sensor was maybe intermittent so I replaced it and now the engine will not start at all. I've been through every schematic I can find and traced and checked wiring to no avail. There are no codes from the PCM. There is 12v to the coil pack while cranking and sometimes when turning the key to start from the off position I get spark but only one time. The PCM seems to turn of the ignition system by not grounding the ignition coils or the injectors. I've tried other PCM's from running vehicles of the same year. The ASD is right, there is 8v to the injectors and feedback voltage to the PCM. Is there a reset on the PCM to initialize a timing sequence? The crank sensor is new also. I have a snap on scanner that tells me the two sensors are working al though I don't think it can count the number of pulses it sees. Please help.
ANSWER: Hi Larry,
I don't know of any reset of the pcm, unless you have an alarmed anti-theft system, but even that allows for a start followed by a shut-down after a couple of seconds. But if that were the case and you weren't getting a good start, then maybe the loss of spark is in fact the theft system shutting it off.
The voltage on the injectors should be 12v (of course while cranking it will be driven down to maybe 8V) because they are on the same circuit as the coil pack.
You could check the voltage on the cam and crank sensors: orange wire should be 8V, then if you turn the engine over by the crank pulley bolt by hand you should see the voltage oscillate between 5V and 0.3V several times for each revolution of the crank, as measured between the other two wires of each sensor.
Keep checking for codes.
And try all three spark plugs' caps on the front side to see if there is continuous spark from any of them. It could be a weak coil pack. Is the coil pack itself tightly mounted as that is its ground?
Before you told me all the details I thought of an 'old friend', the mixture being to dilute due to an egr that is struck ajar. You could check that and lubricate its stem with WD-40 and move the stem back and forth with a screwdriver tip in the stem slot.
Let me know what you learn and if you have another question.
Roland
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QUESTION: Thank you for responding and so quickly, wow. I didn,t mention and should have that I connected atest light to the three wires on the plug for the ignition coils on a van that runs and this van. The light keeps flashing on the working van and not on this one. That is 12v to the light and then to pins 17,18, and 19. The PCM doesn't keep grounding the circuit. I did'nt know if the PCM would stop the ignition for any reason. It seems to me that cutting the feed would be appropriate if it is not going to turn on the PCM output to fire it. So I guess my question would be then, what would happen if the cam sensor did not see the 2 pulses for #6, the flat spot for #1, etc. or if the cam and crank gears aren't aligned? Keeping in mind of course the van ran smooth before changing the cam sensor, when it started. We also checked wires and grounds for all we could find using schematics from alldata. I wish it was simple to read why the outputs are not turning on while cranking. Does the egr tell the PCM to stop the ignition? Or the TPS? Thank you again so much.
AnswerHi Larry,
Yes, if the cam sensor signals were inadequate/missing, then I believe that neither the injectors nor the spark coils would fire appropriately and at the correct times. That is why I suggest that you take a look at the voltage pulses, particularly from the cam sensor wires when you turn it over by hand. Absent good signal to the pcm from that sensor I can see why you would not get any pulsed grounding of the three spark coils. Nothing tells the pcm to shut off the pulsing except a lack of valid signals from the cam and crank sensors which will cause the pcm to disconnect the asd and thus kill the 12v to the coil, fuel, injectors as a safety feature against a fire.
The egr is not related to the ignition at all, just the mixture, and not really to your present issue.
I would expect a code 54 from the fault code readout if the cam sensor were "out", but it might be a weak pulse rather than no pulse.
When you put in the cam sensor did you leave the paper spacer on its tip, and did you press the sensor against the cam surface and hold there while you tightened it down? That is what you are supposed to do.
So I think you have your finger on the issue, its just a matter of proving you don't have good pulses from the cam sensor, and then correcting that. Let me know what you learn, thanks.
Roland
