Car Starts, Dies

[tricky lugnuts]

Hey everyone . . .

Looking for some feedback on an an electrical issue in a 1971 Dodge Charger.

I just got done putting the engine back together with new cylinder heads, new intake, new carb, new alternator. The car starts right up, but dies immediately.

I've already replaced the ballast resistor (my first thought) and double checked all the wiring - seems to be intact.

The one thing I noticed is that if I hold the key in the start position the car will keep running until I let go of the key, then it dies right away.

I've got a new ignition switch on the way from NAPA. Is this going to solve my problem?

Also, it's just the switch - can I just reuse my old key and tumbler in the new switch? And how big of a pain is the switch to replace? I've got the factory service manual, I just haven't taken a look yet.

[John_Kunkel]

The firewall bulkhead disconnect is the most likely source of your problem, find the double blue wire connector on the ballast and trace it back to the bulkhead, remove the connector and clean the contacts.

The brown/blue wires on the opposite side of the ballast provide ignition power in the Start position but shut off in Run; Run is powered by the double blue connector.

[tricky lugnuts]

Thanks -

I was planning on doing that tomorrow, because of all the stuff I moved around and pulled around and wiggled around changing all the parts, something may have come loose.

Got the ignition switch coming just in case, though. . .

[tricky lugnuts]

Alright - so this is getting kind of annoying . . .

Checked the bulkhead - everything seems kosher.

I'd already been in there: cleaned everything up and slathered it with dielectric grease to protect it.

Went ahead and got a new engine wiring harness (my old one was really brittle, cracked, spliced together and generally in poor condition).

That's all plugged in now.

Car still cranks over just fine and starts right up, but the engine dies as soon as I let go of the key. If I hold the key in start position, engine will keep running just fine.

But I've got power at the ignition coil with the key in the run position, which I take to mean that the ballast is doing its job and the wiring is doing its job.

What is going on? 

[nvrbdn]

almost sounds to me like the tumbler isnt sending voltage when the key is in on position.with the key on, is the blue wire powered up?

[tricky lugnuts]

Yep. That's what's killing me.

Start works just fine.

Then, with key in the "run" or "on" position (just back from start), I've got power at the ballast resistor and at the positive connection on the ignition coil.

But the engine dies every time just as soon as I let go of the key and it falls out of the start position. If I hold the key in the start position the engine will continue to run.

[nvrbdn]

ok, im thinking out loud,but the function of start is to send voltage to turn starter. the tumbler has already connected the running components and wouldnt start without them. just crank. so when the motor fires up it is already fulfilling the needs. returns back to run and car dies as if the coil is shorting out. but we already established current with the key in start. i know im already repeating everything you have been beating yourself up over. the coil would have to be loosing power.

[tricky lugnuts]

Hey, I promise not to make fun of ya!

I've been beating my head against the wall on this for a while now - which means it's probably something amazingly stupid!

The coil obviously has juice and is working with the key in start position, since the engine fires up and runs as long as I keep the key in the start position.

So start, everything seems golden.

The coil has juice at the positive terminal with the key in the on position, too - but the engine dies as soon as I release the key from the start position and the key falls back into the "run" or "on" position, even though I still show juice at the coil.

So something must be screwing up in that "start" position to "on" position transfer - even though I have juice at the at the ballast resistor and coil in both key positions. 

[nvrbdn]

if you still have power at the points (im assuming you still have points) and you have power at the coil when the car is in on pos. i am lost. unless you are running electric fuel pump that looses power, but it would still have a lag in time. ill check my wiring book when i get home today.

[tricky lugnuts]

Nope, no points here. I'm running electronic ignition, so I've got an ECU and all that . . .

Everything worked before I took the top half of the engine apart. Problem popped up when I went to start the engine for the first time.

Fuel pump is mechanical, so I don't see how that could be the issue.

I'm with you! 

[squeakfinder]

 Oops. Nevermind.

[FLG]

Could be bad ignition switch.

Try running a wire from the battery to the other side of the ballast resistor (essentially bypassing it) and try to start the car, if it stays running your problem is somewhere on the blue wire coming to the resistor either at the bulk head or before.


Also on 3rd gens the blue wire is spliced off to other things, do you have power windows? see if they work in the run position, or the brake light on the cluster. If either work your problem is at the bulkhead.

Thank Nacho for the knowledge, read WAAAY to many of his posts.

I know you have cleaned and checked the bulkhead but ya never know.

If the wire bypassing the ballast resistor does not work than id say bad ignition switch.

[squeakfinder]

  Allwright. I thought it was 72 when they "started" to place Ecu's in mopar's, and that maybee this was added to this car later. Just thinking something was wired wrong being that it has a new ignition switch and is doing the same thing.

[Nacho-RT74]

If the wire bypassing the ballast resistor does not work than id say bad ignition switch.

still with bad ign switch, bypassing directly from batt the ballast car will start as far engine cranks

[John_Kunkel]

How are you measuring the power at the coil? A faulty upstream connection might allow enough current to light a test light but not enough to run the system.

A jumper direct to the battery as suggested will tell.

[1BAD68]

Sounds stupid but have you checked the engine to body ground strap?
Automotive electrical is my worst area of knowledge but with the key in start position you would have the run circuit grounded through the start circuit but when the key is in the run position, you would then lose the ground from the start circuit.
If the run circuit ground is bad it would have the symptom he's describing. Or not?