Moparts

ECU Dead? Why?

Posted By: cjskotni

ECU Dead? Why? - 10/18/12 10:27 PM

Guys,

I have been troubleshooting electrical gremlins on my Charger now for a few weeks and I thought I had them figured out...

Right now I have an issue where the car will die after 10-15 minutes of running. The idle will start getting real rough and she just dies.

This was the case before and I swapped out the ECU on the firewall and problem solved or so I thought....

No the problem is back. This time I can restart the motor but it won't idle (cuts off) and if I rev it up, it goes up but then after coming down it dies.

Cranking the car from cold, everything acts normal until it warms up.

Now, what I did do (stupid me) was leave the key in the run position over night (12hrs or so) and needless to say, my battery was dead. I charged it back up with a battery charger and fired it up and now the issue is back.

Could that kill the ECU? Could this be a coil issue? This is a brand new $20 parts store ECU. I can't imagine that sucker was bad outta the box. I drove it 20-30 minutes on it before this incident and the Charger ran fine...

Can anybody help point me in the right direction? I have pretty much ruled out grounding issues and the charging system. System was charging when it dies so its not a dead battery...plus I can crank it after it dies all day.

Please
Posted By: meepmeep70

Re: ECU Dead? Why? - 10/18/12 11:00 PM

ECU, your describing exactly my problem,and mine was brand new as well. for 20.00 grab another new one and another for your trunk
Posted By: dogdays

Re: ECU Dead? Why? - 10/18/12 11:01 PM

Coil is failing. I've seen it before. The engine starts fine and when the coil reaches a certain temperature the coil stops working.

R.
Posted By: mikemee1331

Re: ECU Dead? Why? - 10/18/12 11:06 PM

Quote:

Coil is failing. I've seen it before. The engine starts fine and when the coil reaches a certain temperature the coil stops working.

R.

and leaving it powered on for 12 hours with no discharging is the reason.
Posted By: dogdays

Re: ECU Dead? Why? - 10/18/12 11:30 PM

Could be, or it could just be a failure.

The second time I saw this was on a friend's boat, he'd almost get out of the "wakeless speed zone" and the engine would die. It was an inboard-outboard. When I changed the coil with a junk coil I had laying around and solved the problem, he looked at me as if I were Einstein.

R.
Posted By: scratchnfotraction

Re: ECU Dead? Why? - 10/19/12 12:45 AM



this is where i yank the ecu plug and ditch the ecu.

drop in a points dist hooking the dist wire to - side of coil,just remove the stock wire that is there on the - side of coil.

hit the key and ride. when I get the funds up, I jump the BR for a full 12 volts to coil and add an pertronix points conversion with the 40,000 volt flamethrower coil.

done this a bunch of times on mine and others mopars on the side of the road with a points dist. but once converted to pertronix I have never had to work on any ign., problems again.

if I stay with points,i do have to reset them every 3 months or so but thats the way point are.

been running the pertronix set up for the last 17 yrs now and for a tune up it gets a cap/wires/plugs only. never mis-fires and will spin 7000rpm+

good luck changing stock ign. parts out.

Posted By: 72sat

Re: ECU Dead? Why? - 10/19/12 12:49 AM

before you replace anything make sure you ground you ECU, with a wire from your battery. destroyed 2 ECUs because they were not grounded good thru the mounting screws. would start up fine, drive some where would not start. wait, or get a jump; start fine.after you ground it you may still need to get an ECU.
Posted By: ahy

Re: ECU Dead? Why? - 10/19/12 02:15 AM

I would have a spare ECU, coil and ballast. In your shoes, I'd probably change all at once. Not good trouble shooting procedure but a sick coil can hurt the ECU and vica versa.
Posted By: Supercuda

Re: ECU Dead? Why? - 10/19/12 03:28 AM

I don't know where you all are buying your parts, but in over 20 years of driving MoPars I have replaced 1 coil, zero ecu's and zero ballast resistors. Quit buying junk.
Posted By: dart4forte

Re: ECU Dead? Why? - 10/19/12 05:34 AM

Try checking your grounds
Posted By: cjskotni

Re: ECU Dead? Why? - 10/19/12 11:57 AM

Quote:

Try checking your grounds



Before this problem crept up again, I did notice my ground wasn't good on the ECU but I fixed that.

Problem unchanged. I am guessing maybe I smoked it or I am getting lucky with bad parts here...

I went ahead and put nuts on the back of the bolts that secure the ECU to the firewall as my holes are about stripped from all this ECU musical chairs.

This problem really is a PITA because I don't know if it's going to cut off until the it does which leaves me stranded on the side of the road until I can get her to crank.

I guess my car will get a lot of press around town as it seems to be stuck on the side of the road more often than not.
Posted By: RemCharger

Re: ECU Dead? Why? - 10/19/12 04:12 PM

You have a ballast resistor?
Posted By: 70Cuda383

Re: ECU Dead? Why? - 10/19/12 04:26 PM

hard to say for sure, could be anything. but, something electrical is not likeing the heat.

what happened to me was similar, when the car got hot, it started missing, backfiring, and running like crap. it finally stalled and wouldn't re-start.

after it all cooled down, the car started right up.


I replaced the coil because someone here said the coil was breaking down when it got hot.

problem never came back.
Posted By: dogdays

Re: ECU Dead? Why? - 10/19/12 04:26 PM

Swap coils.
R.
Posted By: AdventurerSport

Re: ECU Dead? Why? - 10/19/12 04:31 PM

Quote:

Quote:

Coil is failing. I've seen it before. The engine starts fine and when the coil reaches a certain temperature the coil stops working.

R.

and leaving it powered on for 12 hours with no discharging is the reason.



turning the key to "RUN" energizes the coil, leaving it there for 12 hours can ruin a coil. Swap coil and you'll be fine. I've had the same problem with my black '76 Power Wagon years ago. Good luck!

JS
Posted By: cjskotni

Re: ECU Dead? Why? - 10/19/12 04:55 PM

Quote:

You have a ballast resistor?



Yes I do! I went ahead and swapped the coil and ECU after the car got hot and died.

Basically the same deal...doesn't want to start and when it does, idles like crap and dies out again.

I pulled the ballast resistor. Looks like maybe mine has died? I am thinking this could cause my issues...

The "bad" set of terminals (actually used) = 1.8 ohms
The other set (not used) = 5.8 ohms

This is with the ballast cool now. Normal? Needless to say I have one on the way the afternoon.

Attached picture 7427334-ballast.jpg
Posted By: AdventurerSport

Re: ECU Dead? Why? - 10/19/12 05:13 PM

those can expand when hot as well, causing your problems. Sorry, I thought with Mopars everyone always had spare resisitors and swapped 'em at the first sign of ignition trouble! I had a Power Wagon with wiring issues, and it would eat resistors and ECUs like candy before I figured out the wiring problems.

JS
Posted By: cjskotni

Re: ECU Dead? Why? - 10/19/12 05:23 PM

Quote:

those can expand when hot as well, causing your problems. Sorry, I thought with Mopars everyone always had spare resisitors and swapped 'em at the first sign of ignition trouble! I had a Power Wagon with wiring issues, and it would eat resistors and ECUs like candy before I figured out the wiring problems.

JS



I know they can cuase issues with the ignition, but I thought when they failed, that was it....no engine run at all...even when cool.

Guess maybe a partial failure that heat brings about?
Posted By: RemCharger

Re: ECU Dead? Why? - 10/19/12 05:32 PM

Resistance=heat. the winding could be broken,,but still touching.
The ecu switches the neg side of the coil circuit. so if there was no reduction of voltage,,the ecu would be switching up to 14v instead of 9. But you have a resistor so,, carry on.
Posted By: cjskotni

Re: ECU Dead? Why? **UPDATE** - 10/19/12 11:44 PM

OK so replaced/swapped:

- ECU
- coil
- ballast resistor

The problem is still there. Car will run for about 10-15 minutes...I can rev it up idle it just fine.

Once thing I noticed is that when the electric fans kick on, the engine tends to want to idle lower. I am not sure if the draw from the fans is making this problem worse or not.

Funny thing is, I had run fine with these fans and the OEM 60 amp alternator just fine before. I can't see why this would be a charging issue. Also, despite this, the ammeter doesn't show a dicharge at idle until the fans + light are on. The it starts losing and the battery begins to discharge a bit.

Still this shouldn't kill the engine. After it cuts off, the motor can still crank so battery isn't dead.

Could this be a wiring issue? If so, which wire would cause this so consistantly?

I am stuck here. I don't know what else to check. The only thing that has changed since this issue began is the alternator (went to 100 amp unit). However, as I have said before the car dies even when it's reving up (charging) and the battery has PLENTY left....

Checkd grounds, etc...all good. Plug wires are new. Plugs are pretty new as well.

Any other ideas??? What else can stop a running motor except for a bad ignition circuit?
Posted By: RapidRobert

Re: ECU Dead? Why? **UPDATE** - 10/19/12 11:50 PM

Quote:

Any other ideas??? What else can stop a running motor except for a bad ignition circuit?

dist pickup. I'm assuming the bulkhead has been checked/brass terminals cleaned (small metal bristle brush on the male ones/725147 NAPA male brass 1/4" terminal to clean the female ones)
Posted By: dogdays

Re: ECU Dead? Why? **UPDATE** - 10/20/12 12:10 AM

It's either that or a grounding issue, or a broken wire somewhere, but I'd swap distributors or pickup coils because you've done about everything else.
What kind of slop in the distributor? Can you wiggle the reluctor sideways enough to cause a misfire situation?

I am currently fighting with a ford 400 engine that has a hard miss in the #3 hole, everything else is fine. I'm pretty sure it's either how I put the distributor in or else the pickup is somehow missing that particular tooth, maybe by a few thousandths of an inch.
It can be very irksome.

R.
Posted By: Supercuda

Re: ECU Dead? Why? **UPDATE** - 10/20/12 12:42 AM

If you want to rule out most of the wiring as an issue, simply run a jumper from the battery + to feed side (switched 12V) of the ballast resistor.

This will eliminate everything from the battery to the the ballast. Heck, you could jumper out the ballast to eliminate that too as a temporary test.
Posted By: cjskotni

Re: ECU Dead? Why? **UPDATE** - 10/20/12 12:44 AM

Quote:

Quote:

Any other ideas??? What else can stop a running motor except for a bad ignition circuit?

dist pickup. I'm assuming the bulkhead has been checked/brass terminals cleaned (small metal bristle brush on the male ones/725147 NAPA male brass 1/4" terminal to clean the female ones)



How does one test a pickup to see if it's bad? Can I look at it and see or just odomething you have to swap to find out?
Posted By: Supercuda

Re: ECU Dead? Why? **UPDATE** - 10/20/12 01:24 AM

Quote:


How does one test a pickup to see if it's bad? Can I look at it and see or just odomething you have to swap to find out?



In order of best to worst.

If you have an oscilloscope, you can pull the distributor, hook the O scope up to the leads, rotate the distributor by hand, or with a drill at slow speeds and observe the output. Maybe heat it up with a hair drier to see if it fails when hot.

If you have an analog voltmeter you can put the range to it's lowest setting and do the same test only you will be looking at needle deflection.

You can ohm it out as well, maybe use the heat idea to see if the resistance changes substantially when hot.

If you have none of the above you can swap it out with a known good unit.
Posted By: RapidRobert

Re: ECU Dead? Why? **UPDATE** - 10/20/12 02:26 AM

You could ohm it at the pickup pull apart connector & do it fast while it's still hot. The spec is in the archives. Also put your VOM on low AC volts scale & see if the pickup will generate iirc ~1 volt AC while someone cranks it. Could sub in another pickup/plate or another dist depending on what you have available
Posted By: 70Cuda383

Re: ECU Dead? Why? **UPDATE** - 10/20/12 01:09 PM

Ok, so you've replaced the ECU, the coil, the ballast, and are now checking the distributor.


any chance that this is NOT ignition related? maybe it's fuel related? is your tank vents plugged up putting a vacuum on the fuel system, which then causes air to suck in from the carb to relieve the vacuum in the tank. or maybe your carb is heating up too much and you're getting vapor lock?

next time it happens, quickly check for spark. if you have spark, then maybe your problem is not in the ignition system.
Posted By: dvw

Re: ECU Dead? Why? **UPDATE** - 10/20/12 01:39 PM

Quote:

You could ohm it at the pickup pull apart connector & do it fast while it's still hot. The spec is in the archives. Also put your VOM on low AC volts scale & see if the pickup will generate iirc ~1 volt AC while someone cranks it. Could sub in another pickup/plate or another dist depending on what you have available



Also swap the box and coil with your original parts during the time when it's failed. My bet is neither part will make it start but you should check. The resistance spec for the pick-up coil is aprox 270 ohms. Ohm testing wiring itself is a poor method. It puts no load on the circuit(amperage). Rig a simple tester with a new style head lamp bulb. Disconnect the circuit you want to test from both ends. Hook one end of the bulb to battery positive, the other end of the bulb/tester to one end of the circuit you want to test. Now ground the other end of the circuit you are testing, the bulb should light. I can't tell you how many wires I've found that went open circuit when heated or placed under load. You can check your entire key fed circuit by placing the bulb after the ballast resistor and grounding the other side of the bulb, then key on. Your problem really should be very easy to find. I bet less than 1 hour.
Doug
Posted By: cjskotni

Re: ECU Dead? Why? **UPDATE** - 10/20/12 01:42 PM

These are possibilities but I don't think this is fuel related. This is why:

- fuel bowls on the carb on a HOT (95 deg) day after running the motor in traffic 30+ minutes were maybe 145 degrees. I don't think that would be hot enough to boil the fuel? Maybe I am wrong here Either way, then it didn't make the motor die or hard to start...

- car was running fine for quite awhile and I have done NOTHING to the fuel system to cause this. Same tank/vents/carb/pump everything.

I can try to check for spark next time this happens on one of the plugs and see.


I have a new distriibutor pickup on the way. For $20 I will just get a new one and swap it in to see if that fixes my problem. I read some people online had the exact same problem as me ( car would run until warm then die until cool) and it was the dist pickup.

Worth a shot I guess. Any other ideas if this doesn't work?
Posted By: cjskotni

Re: ECU Dead? Why? **UPDATE** - 10/20/12 08:55 PM

I popped the distributor cap today and found this on the rotor. What would cause this to happen and do I need a new rotor now or can this clean up? Would this cause my warm engine dying issues?

Please advise me guys. I am still learning this car and ignition system!

Attached picture 7428836-IMG-20121020-01039.jpg
Posted By: RapidRobert

Re: ECU Dead? Why? **UPDATE** - 10/20/12 10:44 PM

The rotor looks bent in the pic. I had one like that & I believe it was caused by my carelessness in not setting the cap straight down. I tried to rebend it with no success. It was misfiring/snapping badly. New cap/rotor & all was good. Dont know if I needed to replace the cap as that violated my rule of only 1 part change at a time but I had one handy
Posted By: cjskotni

Re: ECU Dead? Why? **UPDATE** - 10/20/12 11:35 PM

Quote:

The rotor looks bent in the pic. I had one like that & I believe it was caused by my carelessness in not setting the cap straight down. I tried to rebend it with no success. It was misfiring/snapping badly. New cap/rotor & all was good. Dont know if I needed to replace the cap as that violated my rule of only 1 part change at a time but I had one handy



I think you are on to something. I looked in the cap and the button is all chewed up, thats what those filings are all over the rotor it looks like. I am guessing the bent rotor sanded the button down and maybe enlarged the gap to where the spark couldn't arc across it?

I am guessing maybe when hot, this enlarged gap got wide enough to cause this?

I popped the cap a month or so ago (before this started happening) and the rotor was squeaky clean. I guess I got a bit over excited when I put the cap back on.

I have a new cap/rotor on order so we will see if this fixes the problem.
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