Wits end 1992 Dodge D150
 

5.2L, MPFI & automatic transmission.
I've been beating my head on this vehicle on and off for 5 years. After letting it sit for the last 2 years I figured I'd attempt to find the problem AGAIN.
In the past the truck would crank up and run flawlessly but at some point it will shut off and not restart, having to be wreckered in. It might sit up and then by some miracle start running fine or even replacing a part might make it run fine only to be wreckered back in.
NOW, it will crank up and run for several seconds, then shut off and not restart. After that if the key is left in the on position the coil stays energized and the injectors appear to be spraying fuel into the cylinders.
The reason I say this is I removed the coil wire and attached another coil wire with a spark plug on the other end, it would jump a continuous arc for 2 inches to anything it can ground to. I also drained the crankcase of 9 quarts of fuel.
This has been going on all along but I couldn't get the vehicle to reproduce the problem to where I could catch it.
Any Ideas??
Timing and chain appear to be good, compression stroke at TDC on mark. Fuel has been drained and replaced.
This is a list of replaced parts (somewhat it order) from the last 5 years with probably less than 500 miles of operation trying to find this problem. Other minor things also have been replaced.
Distributor ignition pickup
Crankshaft position sensor
Powertrain control module
Fuel pump
Auto shutdown relay / fuel pump relay
Ignition switch
Idle air control valve
MAP sensor
Coil
Oxygen sensor
Throttle position sensor
Fuel pressure regulator
I've got over $850 just in parts, some replaced twice.
I'm way past arbitrarily replacing parts, just give me some ideas.
In reference to the above mentioned continuous arc/injector spraying situation, if I unplug the 2 wire connector to the coil and stick a test light from the battery positive to one of the wire terminals I get a very rapid pulse. This indicates to me something is signaling the injectors and coil to operate at a high frequency much like full throttle situation.

Any ideas?

Since you say the problem persisted after PCM replacement, about the only thing that comes to mind to me is a bad ground. The early SBEC is pretty basic, but normally reliable. They can be shorted out and do funky things if the crank sensor gets shorted out, but I've never heard of one firing the injectors and coil at the same time. So either you have a bad ground allowing the board to backfeed somewhere, or you got 2 bad PCM's in a row. The only other thing I could think of is a short to power on one of the sensors freaking out the PCM. I can honestly say I have never heard of a single case like this before though. The most common problems on those early trucks was shorted out crank sensors causing a no start.

step one unplug EVERYTHING... all sensors and fuel injectors except the coil.... see if condition persists.... If yes then you are left with bad ground, damaged harness or bad pcm (my bet it's this one) if not then start plugging things in one at a time till problem returns....

either the pcm it possessed or being fooled by outside forces

Thanks guys, I actually took a short video of the coil being possessed.
We have done numerous things in numerous sequences trying to get it to reproduce this problem, at lease we are that much closer.

A search for a bad ground began after the DIP, PCM and CPS were replaced. So far nothing. We even grounded from the battery to the block, to the frame and then to the firewall, still no difference.
We could tell during the first cession of checking wires that someone else had the same thought process.

Replacing the CPS and PCM again is not out of the question. We just replaced the DIP, distributor cap and rotor again. The distributor cap had two burned places that looked like a welding arc hit it.

Getting another book is probably going to be the next purchase as we have found several things not covered in the one we have.
I'll also see if I can get some real readings and write them down in the sequence tested.

Can I say it? I dont wanna say it but I have to.......ITS A DODGE!!!!

Gettin rid of mine before it killed me was the best thing I ever did. I cant tell you what it feels like to have to slam on brakes and have your vehicle shutdown on you and steering lockup, meanwhile you throw it into neutral, restart, put back in gear and barely avoid the wreck.

......and thats why they call it a DODGE

The bad ground would be somewhere in the engine/PCM wiring.... Personally I think this is unlikely

DODGE didn't have as many ground issues as GM, but they did happen. The early SBEC PCM's did fail alot though, and would do strange things if a pickup shorted out.

Well crap, I traced the ground from the negative battery post to the eyelet/body ground to a harness connection to two wires labeled as ground to the PCM.
Also along the way traced another spliced ground from the above wire to another harness connector to a diagnostic connector and to the PCM.
All these tested to be fine.

Another PCM is on order. It's really gonna piss me off if it cranks up and runs fine after replacing it.

Please let me know if the link works.
I ain't real sure about this newer photobucket.
It ain't but a 3 second video, had to edit the beginning and end due to immature language.
http://i175.photobucket.com/albums/w...psjhui0irv.mp4

Yikes....

I'll take that as you could view the video!

Yeah... It says image moved but the play button is there and works.

Have you tried unplugging the crank sensor and cam sensor when it does it? Those are teh 2 biggies that the 5 volt reference feed. If it still does it, then unplug them, plus the MAP, TPS, CTS, and IAT Try isolating the PCM back to just power and ground to eliminate as much of the vehicle as you can. Also, does this truck have a tach? I'm wondering if the tach shows the RPM's or not when it fires the coil. Lastly, it may be worth swapping the ASD relay with another. The ASD circuit is what powers the coil and injectors, and it could be energizing when the PCM is not commanding it to and casing some issues.

Never mess with Dodges but it sounds like a computer problem to me.

I'm going to need to do like you and smoke suggest, make up a sequence, go through it and write it down in order to describe it correctly.
No tach on the truck.
Swapping the ASD and fuel pump relays did nothing different, nor did replacing them.

This is the way I remember it the very first time we started looking for this problem:
It would crank up and run for a few seconds then shut off. Leaving the ignition on you could hear the arcing in the distributor.
If you unplugged the DIP (cam sensor) the noise would go away. Reconnecting the DIP sensor before turning the ignition off, the engine would not start.
Turning the ignition off and then reconnecting the DIP sensor, the engine would crank up and run for a few seconds then shut off.
The sensor then got replaced but the problem persisted.
Doing this too many times would flood the cylinders.

We then thought the CPS (crank sensor) may need replacing and did so, the problem was still there after replacing it. We did not go through any sequence of tests with it.

Replacing the PCM seemed the next appropriate candidate, after doing so the problem was still there.
Now the aggravation really begins. After sitting a week or so and checking wire connections literally everywhere beneath the hood and dash, the damn thing cranks up and runs fine for a few months.
Then we start this cycle again at least 3 more times but replacing more different parts.

Another PCM is scheduled to be here today, hopefully I'll be able to get together an actual written test sequence.
Amongst doing other things.

Thanks guys! I do appreciate it.

When it does run, do you get any trouble codes? Next time you start it up, unplug the cam sensor and see what happens. It should stay running after the engine has started. It sure sounds like your shorting your 5 volt reference to power somewhere from this description as that is the only thing I oculd think of that would cause it to engage the drivers like this. I do know the SBEC was funny about to much resistance on a hall effect type sensor, and is one of the reasons CHRYSLER swapped to JTEC for 96 as it had dual power supplies in it VS the SBEC's single.

Matches are real cheap!!