Stalls immediately upon releasing key at start up

[Pkdupont]

My bronco had been running fine for @ 6 months after replacing the starter.

Now it refuses to stay running upon start. She fires up immediately but as soon as I release the key dies out.

The only obvious wiring issue I found was a broken ground wire in the distributor which I repaired.

Everything else is connected nice and tight. No loose grounds that I was able to find

So far I replaced:
Distributor Cap
Distributor rotor
Coil
Starter solenoid / relay
ignition switch & key cylinder

Testing after every swap and the ground wire repair I have the exact same symptoms. Fires up quick then dies immediately when I release the key.

Any tips for additional trouble shooting options very much appreciated.

 

[75MIKE]

I had a bad Ignition module, but it was just opposite. No start at cranking, but would start when I let off the key. A new module fixed it. Seems like electronic stuff is good for out of the blue problems.

 

[Crush]

My 77 module went bad and did just what you are describing

 

[Broncobowsher]

Points or electronic ignition?
Could also be a bad ballast resistor. Starts on the bypass but has no power in run.
Turn the key to run, use a volt meter or even a test light and check for voltage at the positive post of the coil. Should be 8-12V depending if the points are closed or open.

 

[ared77]

+1 There is a voltage supplied to coil on start up (full 12 volts or so) for better cold start, then a separate lower voltage to keep it running. They do this to make the points last longer. Sounds like you are missing the "run" voltage and you need to use a voltmeter or test light to track down problem. Good luck!

 

[EPB72]

What bowsher said ..then i'd be looking at connections at ignition switch connector then through resistor wire all the way to coil ,,,depending what you find with voltage input at coil.

 

[jckkys]

What ignition module do you have? The '75s should have a green strain relief. Your symptoms sounds like a bad module. The harness between the distributor and module has to be in good shape. There is only a small fraction of a volt generated by the magnetic pickup. Any resistance will it.

 

[Pkdupont]

Thanks for replies

I should have clarified I have the Pertronix 1281
Was hoping to follow up with trouble shooting today but don't think I'm going to get to it.

 

[Broncobowsher]

The points diagnostic (questionable ballast resistor) apply to the Pertronix

 

[Bronco4x4]

Make sure your coil wire is on “run” position from the ignition switch. If you have it on the “start” circuit it will happen. Not sure how much wiring changes were made.

 

[triracer67]

As mentioned, check for 12v to Pertronix in on/run position. They require 12v to operate. Some folks run a separate power source just to Pertronix to ensure solid power. Also, they are finicky and may have gone bad.

 

[Teal68]

Did you change anything right before this started happening, or did it start on it's own?

 

[DirtDonk]

You can also disconnect the small Brown wire from the starter relay/solenoid's "I" post.
When you do this and the problem stays the same, you can look to the wire between the ignition switch and coil.

Some Pertronix Ignitors work fine on lower voltage, while others work very erratically. If your voltage has dropped at the Red wire due to something going wrong with the wires being used, it's possible that this issue cropped up due to that.
When you turn the key to START, you get the extra voltage from the starter relay and things work at that point.

So as was said by the others, with the key in the ON position, measure voltage at the coil's positive side.
Is your Ignitor distributor module's Red wire sharing the same connection with the coil? Or was another wire run for the distributor power?

Paul

 

[DirtDonk]

And keep your old parts until you determine the problem. Of all the parts you replaced usually only the starter relay and ignition switch are common culprits. But new parts become problems of their own when you think you've got one aspect fixed, only to find out a new part was bad.

Paul

 

[abn373]

This happened to me when I switched to a GM HEI distributor. Damn, I am trying to remember what the issue was, but I know it was 100% wiring problem. In my case I wired something back up wrong.