Chrysler Repair: 2000 3.8L: intermittent spark, crank sensor, haynes manual

Question
Hello,

Thanks for taking the time to read this over. I am having an issue with a 2000 grand caravan. It has a 3.8L engine and Automatic transmission (I think they are all automatic).

The van was running fine (don't they all before they break) until we stopped for gas. Turned it off, gassed up, and would not restart.

Got it back to the house and noticed that the spark was intermittent. Also noticed the plugs were in poor shape while I was checking spark. Appeared to have fuel at the plugs.

I have done the following so far:

Changed the plugs (not the problem, but they were worn)

Changed the wires (after getting all the way to the back three nothing used was going back on, wow that was an adventure)

Checked the coil pack and found the resistance was a little off the top end (per the haynes manual .45 to .65 ohms at 70 to 80 degrees, was reading .69 ohms at 71 degrees) Changed it out with a new one.

Checked fuel pressure at the rail and got 50 psi on attempted startup, book called for 49. First thing I checked actually since we had just gassed up. I was thinking possibly fuel filter or pump.

Where I am now is, I get one spark for every 3 or 4 compression strokes. I tested this on plugs 2, 4, and 6 with pretty much the same results on each.

I am left thinking it's either the computer (which was clear of codes using my handheld scanner) or an input sensor of some sort. Unfortunately i am way over what the haynes manual covers on this one. I don't know what sensors would effect it, or how to test them.

Any advice would be greatly appreciated.

Thanks again for your time,

Brad  

Answer
Hi Brad,
Thanks for the complete history. It could very well be either the cam or crank sensor. You can test them with a voltmeter while turning the engine over by hand with the ignition in "run". The sensors have 3 wires: orange with 8V on it, a black/light blue which is the sensor ground, and third wire will be the signal which should oscillate between 5V and 0.3V when measured against the ground. The voltate should pulse multiple time per revolution, more frequently on the crank than the cam. Use fine needles to probe the wires at the plug/wire sockets. I believe the Haynes discusses this as a test for sensor function. Let me know what you find, please.
Roland
PS Sorry for the delay, I just found your question in the 'pool' to which it had been referred.