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Car starts then immediately dies

Hi, I have a 1973 Dodge Challenger with rebuilt 383 4bbl. With the key in start position the engine “starts” but then immediately dies when I let the key off to run position. Has spark (did spark test and actually put in new plugs) and fuel going into carb. Tried spraying in carb cleaner while trying to start but no luck. Just got flames eventually!! Battery is new and ignition switch was recently changed.

I did try attaching a jumper wire from the + battery post to the + side of coil and it started and ran. Had it in for less than a minute but thought that meant is was the ballast resistor. Changed that but still the same problem. Thinking then it was maybe some weird wiring issue, I ended up just swapping out the engine wiring harness but that still didn’t work.

I think I’ve exhausted all YouTube searches so any suggestions would be greatly appreciated!!

The ballast resistor may be bad,

Tester

Did replace the ballast resistor but unfortunately it didn’t fix the issue.

allpar.com is my go-to place for Chrysler info. There are several forums there and one or more apply to the older vehicles. Good luck!

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Can you jump the ignition switch (run position)?

Not sure if this is what you mean but did connect a wire from the + coil and + battery terminal and it did start and stayed running. Changed the ballast resistor thinking that was the problem but it didn’t solve the issue.

I would be looking for an electrical diagram, and tracing that + terminal backward to see what feeds it. One of the things that surely feeds it, at least indirectly, would be the electrical side of the ignition switch (not the mechanical lock part). It sounds like the switch is feeding it in the start position, but not in the run position. But, be sure to measure the resistance of your old and new ballast resistors. You might have gotten a bad one, or fried both.

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One additional fact I should mention is the car was starting and running fine working before the current start/no run issue. Worked for a while after the ignition switch and battery were replaced so wasn’t thinking it would be an ignition switch issue but I’ll check that. New ballast resistor is also reading 0.5 ohms which I think means it’s working…

That’s very little resistance. What is the spec for that resistor?

Maybe you mean 0.5K ohms or…

With the ignition in the run position measure the voltage at both ballast resistor connections.

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BR is rated 0.5 - 0.6 ohms (meter scale set at 200 ohms).

Do you mean flames shooting from the carburetor?

Yes, shot in a bit too much carb cleaner I think…

Any reasons why I would get no voltage reading other than I’m measuring incorrectly?..

Just a WAG, timing Chan jumped a few teeth.

That’s definitely beyond my DIY skills!!

You need to consider a faulty ignition switch or a poor connection at a bulkhead (also known as a firewall) connector.

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This is the classic sign of a bad ballast resistor. Since you’ve replaced it, check the wiring to it very carefully.

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Then the problem might be with ignition control module.

Tester

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Will try this.