76 2.0, 120k miles, all stock engine parts except for Crane Ignition. Engine runs on after shutdown for 3 to 5 seconds. All engine parts working, thermostat, aux air regulator, no vacuum leaks, motor runs beautifully and pulls hard, engine idles after warmup at about 600 rpm. I tried adding a diode to the lead from the alternator to the generator light, that made no difference to stopping the run on after shutdown. Any other ideas to suggest that might fix it? (besides popping the clutch to stop the engine)

timing too advanced ?

Would running higher octane gas help?

Did you change your tail lights recently? Using a single filament bulb instead of the correct dual filament can make the engine continue to run.

Edit - Never mind I just reread your post it only runs for '3 to 5 seconds'. I don't think the tail lights would affect this.

I second timing.

I removed the dizzy recently to install new trigger points. I did not loosen the adjustment bolt, only removed the hold down bolt to get the distributor out. But that may have altered the timing slightly non the less. I am taking the car in to a very good mechanic next week for it's required smog check, so I will ask him to check the timing before running it for smog. Thank you for your suggested solution.

Ignition switch.

I disagree with the timing being the culprit.

If the ignition is OFF then the "sparks" should not be firing and it wouldn't matter where the timing is set.

Another thing that can cause run-on (other than an electrical problem) is if the heads are way too hot.
Do you have a temp sensor to tell you if the engine gets hot?
Does it run-on after a very brief startup or only after a long drive?

I think I read something here a while back about the same issue and it turned out to be the Crane ignition.

It runs on even after short drives. The temp outside has been cool and I don't think the engine is running hot. Since I removed the rain tray the engine has been running cooler than ever. The cylinder and oil temps seem fine. Will check timing before smog check and go from there.

Injected, right? In theory, all fuel should cut off instantly when the key is turned off. That means no run-on from ignition or hot-spots. You need fuel for run-on.

So, either you have a lot of fuel loaded up in the intake, or your FI is continuing to add fuel.

I would suspect the ignition switch. Or maybe something else is feeding back into the ignition circuit?

You'll want to isolate the problem. See if unplugging the trigger points or the four-pin plug at the relay board kills the engine. If so, you've got something continuing to power the fuel injection.

--DD

Yes, FI. Dave, can you be more specific on location of 4 pin plug/relay board location you're referring to? Want to be sure I'm pulling the right thing to check, thanks.

Here's relay board, pull what?
Click to view attachment

Bottom-right on your photo. (Left-rear as it shows in the car.) Four pins, white wires.

--DD