Moparts

ECU problems?

Posted By: 73ChargerSE

ECU problems? - 02/01/09 02:20 AM

Was having a misfire problem with my Charger. Got the plug wire fixed and was driving it a bit. While I was driving it seemed like it was a bit shakier than normal. After I got the car parked again, it wouldn't start anymore, just keeps cranking.

-The car has fuel (clear bowl sights)
-Thought it was a coil or coil wire, tried both of those, didn't work
-For a while my oil pressure gauge wasn't working at all, finally got that to come back (engine harness related)
-I've messed around and unplugged the engine harness connector a few times and plugged it back in and that didn't help.
- I am getting full voltage from the blue ballast wire
-HOWEVER, I am only getting from 4-5 volts at the coil. I tried 3 different coils, same story.

What could be causing it not to start? Would it be my ECU? Voltage Regulator? Distributor?

Thanks for any help
Paul
Posted By: denfireguy

Re: ECU problems? - 02/01/09 02:27 AM

Quote:


-HOWEVER, I am only getting from 4-5 volts at the coil. I tried 3 different coils, same story.

What could be causing it not to start? Would it be my ECU? Voltage Regulator? Distributor?

Thanks for any help
Paul


With the key in run position, that is the right voltage with the engine not running. In start position with the engine turning over, it should jump to 12V. The voltage should return to 6V with the engine now running.
Take a plug wire off and see if you have any spark while the engine is turning over. If you do not, suspect the ECU or the distributor.
Craig
Posted By: moparsquid

Re: ECU problems? - 02/01/09 02:28 AM

sounds to me like to much ohms resistance in the balast resister,a friend had a 440 in a dart and it would not start until i changed the b/r to a lower ohms unit.
Posted By: zrxkawboy

Re: ECU problems? - 02/01/09 02:32 AM

might be helpful:

http://www.moparaction.com/Tech/archive/roadside.html
Posted By: 73ChargerSE

Re: ECU problems? - 02/01/09 02:35 AM

Ballast resistor was a NOS unit, I tried another ballast resistor (not sure if it was good or not) and that didn't work either. I am not getting any spark at the distributor cap. I thought I should be having about 9 or 10 volts at the coil at the run position.
Posted By: RapidRobert

Re: ECU problems? - 02/01/09 02:46 AM

(1) take the primary wire off of the coil (-) terminal & w key on tap it to a metal ground & see if the coil secondary wire(held 1/4" from ground) sparks (2) Jump 12V from battery positive post to the upstream side of the ballast & crank it w the key & see if it starts.
Posted By: denfireguy

Re: ECU problems? - 02/01/09 02:57 AM

Quote:

Ballast resistor was a NOS unit, I tried another ballast resistor (not sure if it was good or not) and that didn't work either. I am not getting any spark at the distributor cap. I thought I should be having about 9 or 10 volts at the coil at the run position.


No spark, ECU or distributor. Probably ECU.
Ballast is out of circuit on switch in start position.
Low voltage on coil is a red herring.
Craig
Posted By: 73ChargerSE

Re: ECU problems? - 02/01/09 03:34 AM

Well I swapped out the ECU for one that was in a running Duster that I've got. No go on that one either. The thing that freaked me out is I realized that when I turn the key off from the start position, the motor reverses it's rotation a small amount and pushes air out of the carburetor.

What the heck is going on with my car
Posted By: RapidRobert

Re: ECU problems? - 02/01/09 02:45 PM

Quote:

when I turn the key off from the start position, the motor reverses it's rotation a small amount and pushes air out of the carburetor.

I've seen that a few times, I just assumed it was from the eng being tired.
Posted By: Anonymous

Re: ECU problems? - 02/01/09 02:57 PM

Quote:

Quote:

when I turn the key off from the start position, the motor reverses it's rotation a small amount and pushes air out of the carburetor.

I've seen that a few times, I just assumed it was from the eng being tired.



No what usually causes that, either key on or off, is that a residual spark occurs, is fed through to a plug, and fires a small amount of "compression" in a cylinder
Posted By: RapidRobert

Re: ECU problems? - 02/01/09 03:02 PM

got it, that makes sense.
Posted By: Wedgeman

Re: ECU problems? - 02/01/09 03:26 PM

Hi,
Running from the start, may be you overlooked something obvious ( it is often the case, by experience !)

IF it fires back in in the carb, it means you have spark.......non ?

Voltage is normal,
Ecu is ok...
wires are fine

Is the cap worn or damaged ? if not...
The advance plate moving freely? (not stuck)

Lessen the advance just a notch on the dist to start..(not supposed to turn backwords when turning off)

Did you check the level in the carb ?
Clogged primary jets ?
Have you tried putting gas in the carb and start it? if it does you'll know where to look..

Dan
Posted By: ThermoQuad

Re: ECU problems? - 02/01/09 06:39 PM

It's either the pickup in the dist or the timing chain. I'll go with the
stretched /jumped chain crystal ball guess
Posted By: 73ChargerSE

Re: ECU problems? - 02/01/09 06:41 PM

The motor is brand new with new summit double roller timing set. It has less than probably about 50 miles on it. I haven't even had the car on the street enough to get it registered. I'm hoping it's not my timing chain.
Posted By: 73ChargerSE

Re: ECU problems? - 02/02/09 05:18 PM

Posted By: denfireguy

Re: ECU problems? - 02/02/09 06:54 PM

Quote:

Well I swapped out the ECU for one that was in a running Duster that I've got. No go on that one either. The thing that freaked me out is I realized that when I turn the key off from the start position, the motor reverses it's rotation a small amount and pushes air out of the carburetor.

What the heck is going on with my car


You did not say if you have a spark yet with the substitute ECU. I forgot to include coil as another possible culprit. To trouble shoot the coil, disconnect the wires going to the negative terminal of the coil. Hook a piece of wire long enough to get to a good ground. Pull the high tension wire that comes from the coil out of the distributor. Place the wire within a half inch of a ground. Take the wire from the negative terminal and tap it to ground. It should develop enough voltage to produce a spark on the coil secondary.
Or take the coil out of the donor car you got the ECU from and swap it out. If the coil is working, and the ECU is known to be good, then the problem is in the pickup in the distributor.
Craig
Posted By: 73ChargerSE

Re: ECU problems? - 02/02/09 08:54 PM

Well I put the substitute ECU and put a new ballast resistor on it and it fired right up. So I think both of those were bad.
Posted By: RapidRobert

Re: ECU problems? - 02/02/09 10:48 PM

you might sub both of the bad items back in there(1 at a time) that way if only 1 was bad(which'd be my guess) you wouldn't be tossing a good part that could go in your glove box as a spare. but maybe after this you dont want to lay eyes on an ecu or a ballast for quite awhile.
Posted By: denfireguy

Re: ECU problems? - 02/03/09 01:31 AM

I don't know, I think I would leave them both in there and walk very quicly away.....
Posted By: 68CoronetRT

Re: ECU problems? - 02/03/09 02:02 AM

Quote:

Well I put the substitute ECU and put a new ballast resistor on it and it fired right up. So I think both of those were bad.



My money is on the ballast being bad. You said the ECU worked in your Duster right?
Posted By: 73ChargerSE

Re: ECU problems? - 02/03/09 02:31 AM

I ordered a new ECU box. Went with the Mopar Orange. It was only $45 compared to the $58 Checker wanted for a Niehoff. I had to put the ECU back on the Duster, but when I get the replacement, I'll check the ballast resistor and test the one I took off. We'll see what happens
Posted By: RapidRobert

Re: ECU problems? - 02/03/09 02:35 AM

The MP chrome box would be a much better deal(more dependable/doesn't retard timing) than the orange box. any way you could call & change your order. Trust me on this one.
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