Good Evening,

I am working on my 1972 Charger with a 440 and have run into a problem that is a bit odd.

The car runs very well, but will periodically die. I can then not get it to start, I am not getting any spark at the coil. I have replaced the coil and balast resistor (it has several cracks along the back). I have also replaced the battery cables and ends, and cleaned the engine and body grounds. I have traced the wiring harness to see if there were any wires grounding out.

Here's the odd part, if I disconnect the battery for a few minutes and reconnect it, the car will fire right up. Coincidence?

So, does this suggest the voltage regulator or the electronic ignition control?

I'm stumped. Also, if anyone has any good diagrams of the wiring and voltages I should be getting at critical components, that would be great.

Much Thanks, Jake

 

I am no electrical expert, but let me get the ball rolling. Is it possible there is an issue with the starter? Have you tried a different battery? I know these are very simplistic suggestions, but maybe they are worth checking.

 

There is a nice simple diagram at the end of this article for the electronic ignition.

Here are some nice diagrams for the charging system.

Joe.

 

Those are some great articles. I will definitely review those.

As for the starter and battery, no, they have not been replaced. The battery is fairly new, I don't know how old the starter is. The car will crank until battery dies. I could see the battery being a possible issue, but that wouldn't explain the car dying while at idle. Or would it? I am not an electrical expert either, so I am not sure where else to look.

Thank you for the information.

Jake

 

It sure might explain it dying if the alternator is not charging the battery. Get her running and pull the positive battery cable, good alternator and you should stay running, bad alternator means you been running off the battery and the engine will die.

I had a car that acted like it was running out of gas, it was running out of juice in the battery ..... Bad alternator.

Joe.

 

This really sounds like a ballest resister but you said that it was replaced. Assuming that you replaced with the correct one I would go with the ECU. Check ECU grounds and connections. You say that when it dies you have no power at the coil, is this checked with a voltmeter? With no power at the coil do the headlights come on? If so I would rule out a dead battery but if you wanted to check charging when you can get the car running take that same voltmeter that you used to check coil voltage and check battery voltage. Should be around 14.2v (+/- .5) with car at idle no load. Speed up RPM to about 1500rpm and turn on all accessories, lights, fans ect.. voltage should still be around 14 or so and your on dash amp meter should be to the positive. Hope this helps a bit any way.

 

One more thing here about removing the battery cable while running. If you do decide to do this always remove the negitive cable not positive. Also, do this quick do not leave the cable dissconnect for more than a few seconds (assuming the car stays running). the battery is what stabilizes the voltage and if removed from the circuit (by disconnecting) charging voltage will continue to climb and can burn out lights, ECU's and even stereo's if on at the time. This procedure is not recommended in any vehicle with a ECM because of this.

 

Just my luck. I am trying to get the car to the shop this morning to get the front end aligned after installing my fresh front end and it won't start.

My previous battery disconnect theory was wrong. I tried it again this morning, let it sit, but still no joy. I checked all the connections at the ECU, battery, start, etc. Everything is clean and connected.

I believe it's the right balast resistor, not sure how to confirm that. I bought it at a regular auto parts store.

The car cranks over very well, so I think the battery is ok. Also, the no start would likely rule out the alternator since the car depends on the battery at start up? Right?

So, I think that leaves me with the ECU.

 

Your probably right but it could be in the distributor too. Can you check for voltakge at the coil + terminal with the ignition on?

 

Ok. Here is a quick update. I pulled the ECU and cleaned the contacts again, however, this time I also cleaned the mounting surface where it mounts to the firewall and the surface on the back of the ECU. Damn car fired right up....

So, does the ECU actually ground thru it's mount to the firewall and not a wire ground? Both? Or did I just jiggle it enough to get it to fire once?

Jake

 

Good catch and yes it does as does the voltage regulator you may want to clean that up also

 

There I go, forgetting to include a standard disclaimer when giving electrical advice "never trust your property or well being to some nut on the internet".

 

Thank you everyone for the advice, it's all very useful. It's really nice to have people to bounce ideas off of and get new ones.

The good news is, the car is at the shop getting the front end aligned, so I should actually be able to enjoy some cruising this weekend. No more projects for a while and hopefully I hae solved the ignition issue.

Thanks, Jake

 

That was a wierd one! Glad you got it working. Have fun crusing!!!