Was running very poorly. Would start right away, idled semi-OK. Ran very rough when pushing on gas pedal. Could barley move under it's own power. Used car lot owner had changed the transaxle and couldn't get it to run right again. He eventually gave up sold it to me at a loss for far less than book value.

I replaced the crankshaft position sensor, no luck. Found a loose bolt in one of the extra holes in the flexplate that was not screwed into anything. Removed it and did some other diagnostic work mainly tracing wiring, looking for short or open curcuit. Never found anything but at some point everything suddenly seemed fine. I put the old crank sensor back in and it still ran fine. Engine started and ran 100%, getting 22 MPG for 6 months and thousands of miles then it suddenly started acting exactly the same as when I bought it.

I tried the crank sensor that I had previously put in/taken out with no luck. Wiggled wires and checked everything again as before. It still started and idled OK but ran so rough when applying the gas pedal it would barely move under it's own power, stalling/missing/backfiring, instead. I parked it for lack of knowledge and experience enough to fix it. Bought a 4WD kia. We need 4WD or AWD becasue we live at the bottom of a big hill and when it snows ... well ... you know.

Fast forward about 6 years and I'm trying to get this back on the road so I can retire our "second car" a 250,000 mile '91 GC. I charged the battery and it started right up, idled semi-ok and barely got istelf into the garage. After poking around and trying to remember what I had done sevral years ago, now it won't start at all and there is no spark. Starter circuit is fine. There is plenty of spark when testing with Snap-On MT2500 scanner via diagnostic connector so I'm assuming the coil pack, wires and plugs are all good. Checked wiring continuity from (3) connectors at crank sensor/cam sensor/coil pack to ECM connector, all good. Scanner showing intermittant crank sensor signal when cranking on starter. Tried new crank sensor, same result. Tried remanufactured ECM, same result.

I could find no cracks in the flexplate after removing inspection plate and starter. I read elsewhere that the flexplate can detach at the center. Is there a way to check this without removing the transaxle ?

This engine has a remote keyfob/door lock controller and factory alarm. I cannot find any info about this system. Could it be the main source of or at least contributing to my trouble ? Come to think of it, way back when I first got it going correctly, I had the top of the dashboard off and looked at the alarm system controller. OK so I do know that much about the system, where the controller is but that's all I could find.

I'm thinking I should have spent the money on a factory repair manual instead of a remanufactured ECM. Anybody have any ideas for me to try, I'm listening.

 

The alarm system shuts off fuel so if you don't have spark it is not the issue. If you have no spark, go to the coil connector and disconnect it. With a test light, and the key on, check for power to the dark green and orange wire. It should have power for a couple seconds after turning the key on and while cranking. Also check the other 3 wires by connecting the test light to battery positive and probeing the wires while someone cranks it over. The test light should flash. Let us know what you get.

 

here are the diagrams you wanted

 

Thank you Jumpdrive2. I'm going to print these out (hope that's OK) and double check the colors and continuity.

 

Tizzy1, I did the first part of the test as you described. I put the test light into the coil pack connector testing the green/orange wire. The test light came on for about two seconds when I turned on the ignition switch.

I do not have a helper today so I modified the test slightly from what you told me to try. I was able to secure the trest light probe into the connector, one wire at a time, the same as I did when doing the first part of the test. I watched from where I was standing next to the driver's door, reaching in to operate the key while holding the headlight dimmer stalk/switch back (factory alarm) and craning my neck so I could see the test light. The test light did not flash while cranking the engine over on the starter. I hope this does not effect the outcome of the test. The only way I can see it would is if the engine has to be cranking over first for a couple of seconds before probing the "other three" wires in the coil pack connector ? Lead on and I'll keep trying whatever you suggest.

 

Not sure what else to do, I measured the resistance across the pins on the Crankshaft Position Sensor. I did the same on a newer aftermarket sensor as well. They are not the same but similar. I got 5K and 20 K on the original one, 30K and 40K on the newer one.

Taking a day or tow off to enjoy the holidays and then I'm going to pull the wiring harness apart to inspect evey inch or wire going to the sensor.

 

I unwrapped the wiring from the ECM to the crankshaft and camshaft position sensors. The tricky part was undoing the injector plugs underneath the intake manifold. I finally managed to get them undone and pull out the harness. Found nothing wrong, no short circuits, no broken wires.

Tizzy1, I redid the second part of your test - correctly this time. I misread it at first and had the test light grounded, instead of on the battery positive post. I used a starter button plugged into the starter relay socket and the ignition switched on. The test light flashed but seemed intermittant and did not light at all, everytime I cranked the engine over. I ran the starter for about 10 seconds each time.

I also found in the Snap-On Troubleshooter cartridge a cam and crank position sensor test procedure. With the ignition switched on and cranking the engine over on the starter, both sensors intermittantly flashed yes/no. A steady "Yes" meaning good. A steady "no" meaning bad. They both were intermittant. The test procedure had me unplug the crankshaft sensor and repeat. The cam sensor showed a steady "yes". I followed the test procedure and next plugged the crank sensor back in and unplugged the cam sensor. The crank sensor showed a steady "yes" also. When either sensor was unplugged, the other one tested OK. When both were plugged in, they both were intermittant. My guess is they are not synched up correctly ?

Both sensors seemed to operate perfectly when not installed. This includes the new crankshaft position sensor I had put in for a brief time, years ago and the original cam sensor that came with the car. I checked each with the oscilloscope and they switched from 0 to 5 volts and back to 0 volts everytime I passed a screwdriver near the end of the sensor. The old sensor switched from 0 to 5 Volts and stayed at 5 Volts until I passed the screwdriver near the end a second time. For some reason the voltage switched and then latched on until I passed the screwdriver near the end, again.

The oscilloscope I have is not an automotive one but it seemed to work in these out-of-the-car tests to verified that both sensors function. I was not able figure out how to trigger the scope to produce a stable image. Instead, the image kept moving across the screen fairly rapidly. What I could see however looked like solid square waves that seemed to be fairly consistant. It appeared there was a series of four square waves from the crankshaft sensor. I was unable to determine how many from the camshaft sensor because by now the poor tortured starter motor was getting hot and the battery had been almost completely discharged.

I took the battery out an put it on my trickle charger and will go back at it tomorrow.

Oh, one more thing I did a compression test on one cylinder. 112 PSI after 4 power strokes. The engine sounds normal while cranking over. I don't believe the camshaft jumped timing. I beginning to believe the timing ring has somehow slipped on the flexplate. I'm really not looking forward to taking out the transaxle only to find nothing wrong there either.

Does anyone have any more suggestions what to look for ?

 

When the test light flashes, that is the PCM grounding the coil packs. When it stops, it must be loosing signal from one of the sensors. When the flex plate cracks, it does so near the mounting bolts so you would have to pull the transaxle back to check it. It was pretty common back then. Otherwise one of the sensor wires could be shorting to ground but sounds like you have checked them pretty well.

 

Tizzy1, I appreciate your input. I hadn't thought of just moving the transaxle a little to look inside the bellhousing. I was thinking I had to remove it completely but what you say makes sense. Obviously I am still hoping it's something requiring less work but I would have had it out and in again by now. Stubborn, I guess.

Now that I know where to look for the cracks, I'm encouraged. What has me thinking it's not cracked is, I never heard any of the typical loud rapping/clanging noise cracked flexplates usually make. I've run across a few in the past on other makes and the noise is unmistakable. I'm assuming the flexplate in the is Dodge would have been making the same helatious noise I've heard in other cars, if it is cracked. Am I wrong about that ? Are they sometimes cracked but remain silent even while under a slight load.

If I could find a mechanical discrepancy between the crank timing windows and cam timing groove, I'd be convinced I need to pull the transaxle. Trouble is, I cannot find info on where the flexplate timing windows or cam timing groove are in relationship to TDC. Is this info published anywhere ?

 

If you had a lab scope, you can put it on the sensor and see what is missing.

I have seen many flex plates cracked and not make noise. It's a tough situation, been there, don't want to waist my time pulling it to find out it's not cracked. I look at it this way.....it's probably either that or the harness to the crank sensor. Much easier to check the harness with the trans on the floor.

Have you watched the flex plate through the crank sensor hole? Does the plate appear to be centered and run straight?