Starter engages but engine stalls when key is released

[crushers]

You are getting voltage through the starter (Key in Start Position), but not through the regular ignition via the Ballast Resistor. You may have a broken wire, or a bad ballast resistor.

There is a black wire that comes off the starter solenoid and goes to the (+) side of the coil. This provides 12V when the starter is engaged.

There is another wire that comes from a metal box (Ballast Resistor). This should be "Hot" (+12 V) wne the ignition is in the ON / RUN position.

Put a meter on the coil (Black to Ground, Red to Coil (+)) and test my theory.

You can run a wire direct from +12V to the Coil (+) and if the ballast resistor/wiring is the problem - the engine will continue to run after you start it. Don't run it like this too long, or you may burn up the coil.

Regards -

Rocky

it has been about 3 decades since i drove gasser 40s. i picked up an old 1974 that would sound like it wanted to run but as soon as the key was returned to "run" it would die. this post saved me a lot of headaches. thank you for posting it up.