Electrical issue question starting car

[transam]

Hi,
Car started fine yesterday. Today I turned the key, car started right up and as soon as I released the key she died. Did this several times with the same ending. If I hold the key all the way in the start position, it appeas to want to stay running until I release the key. Seems this happened on another mopar I had. Am I correct that this is caused by a faulty ballast resistor?

 

[pschlosser]

Am I correct that this is caused by a faulty ballast resistor?

You are right. This is the first thing I would check. If the ballast resistor looks good, then check the wiring through it, all the way back to the ignition switch.

While cranking, the ballast resistor is bypassed until you release the key to run position.

 

[540HemiCuda]

Yep. We used to carry a spare ballast resistor in the glove box. They were that unreliable.

 

[transam]

You are right. This is the first thing I would check. If the ballast resistor looks good, then check the wiring through it, all the way back to the ignition switch.

While cranking, the ballast resistor is bypassed until you release the key to run position.

Changed ballast resistor and still having same problem. As long as I hold key in the start position the car will run. As soon as I release the key the engine stops? I think my ECU may be faulty.

 

[540HemiCuda]

Check your incoming power on the run circuit TO the ECU first.

 

[Challenger RTA]

Bulkhead connector and steering column plug. DBL WHT tracer. Push the connectors together first. Might be loose.

 

[pschlosser]

on these 50+ year old cars, the connector points through the electrical system can get "iffy." A good cleaning of each connection point can give you piece of mind and may last another 50 years. There are some spiffy tools to help you remove the crimped (bullet and spade) connectors from the plastic connection points without harming them. They look something like:

 

[transam]

You are right. This is the first thing I would check. If the ballast resistor looks good, then check the wiring through it, all the way back to the ignition switch.

While cranking, the ballast resistor is bypassed until you release the key to run position.

OK folks. Got it. I read a post on here about the connectors to the ballast resistor and elsewhere. So I went out and just wiggled the wires on the ballast connector and the car started right up. The wires looked brand new, but I guess when these cars sit they have a way of corroding inside the spade where eyes cannot see. So I will spend some time and remove the spades and clean and install some dielectric grease on them. Problem solved so far.

 

[transam]

You are right. This is the first thing I would check. If the ballast resistor looks good, then check the wiring through it, all the way back to the ignition switch.

While cranking, the ballast resistor is bypassed until you release the key to run position.

Well I thought I fixed it with a new coil, but today changed everything. So I installed a new ballast resistor and it would crank over fine but no fire in the hole. So I changed the ECU orange box with a new one I bought from Mancini Racing. So now, I can crank and crank but when I let go of the key, the car fires right up and seems to run fine?? This has to be a loose connection somewhere. I pulled and plugged the bulkhead connectors in and out and they look fine. Could my start relay be screwed? My next move is to try and go down under the dash and check connectons there. I did recently install a new ignition switch due to a lost key. Car ran fine with the new ignition switch. I still have the instrument lighting panel out of the car and I don't think that would have anything to do with maybe losing a ground. Any ideas. Endine turns right over and won't fire until I let go of the key?

 

[pschlosser]

Well I thought I fixed it with a new coil, but today changed everything. So I installed a new ballast resistor and it would crank over fine but no fire in the hole. So I changed the ECU orange box with a new one I bought from Mancini Racing. So now, I can crank and crank but when I let go of the key, the car fires right up and seems to run fine?? This has to be a loose connection somewhere. I pulled and plugged the bulkhead connectors in and out and they look fine. Could my start relay be screwed? My next move is to try and go down under the dash and check connectons there. I did recently install a new ignition switch due to a lost key. Car ran fine with the new ignition switch. I still have the instrument lighting panel out of the car and I don't think that would have anything to do with maybe losing a ground. Any ideas. Endine turns right over and won't fire until I let go of the key?

I want to emphasize one point. Understanding. For me, when I understand how something is supposed to work, I can more easily test and validate function, and often find the problem.

One side of the ballast resistor has two (Dark BLue and BRown) wires. The other side has one (Dark BLue) wire.

The one-wire side sees +12V when the ignition is on (but unsure during cranking) and during RUN, the 12V goes through the ballast resistor and out the (two-wire) side where it connects to the ignition coil with (typically) a reduced voltage varying with engine RPM.

On the two-wire side, the other (brown) wire (not connected directly to the coil) is the one that feeds back to the ignition switch, where, during cranking-only (START) it is fed a full 12V.

With that (presumed correct understanding), you are invited to use the wiring diagram and a volt meter to test the RUN and START voltages at the ballast resistor.

What you describe sounds like during cranking, that brown wire is NOT being fed 12V, and when releasing the key to run, the ballast resistor THEN sees the 12V on the one-wire side, and is able to fire up and run before the engine stops spinning (by releasing the key)

 

[Challenger RTA]

Could my start relay be screwed?

No. The starter relay is only for the the starter motor.

 

[Challenger RTA]

Start is Brown and Run is Blue. Don't forget the grounds.

 

[Challenger RTA]

loose connection somewhere.

Ignition switch maybe yes maybe no? Ignition sw plug under the steering column loose? bulkhead connector loose? Spade connectors on resistor and coil loose? Mounting screws for ECU bad connection.

Hot wire it again. it can be done with the bullhead connector under the hood disconnected.


To start the car jump power to the brown wire for starting and at the starter relay were the yellow wire connects. That will turn the starter motor over.
Take note the Brown and Yellow wire only need power when starting.

Run power from the battery to the blue wire on the bulkhead connector. ign 1

It will keep running until you remove the jumper wire on the blue wire.
When the motor is running move the engine harness around. That will tell you if there is a broken wire in the engine harness.
The same thing can be done with a test light or meter when harness is disconnected. Ground the end of each wire and test with test light feeding power to the other end of the wire.

Under the steering column at the plug the same thing can be done. With Yellow start. Brown start and Dark Blue with white tracer run.

 

[moparleo]

 

[70 STARTE Chall]

With the key in run, check if your coil is getting positive voltage. Then check if it is getting positive voltage when you are cranking the motor.