Has anyone ever seen a problem where an apparent short in the starter circuit randomly engages the starter while the engine is running? I think this is an issue with my car.

My current 914 had starting issues from the day I got it a year ago. Since I had a Raby engine in the works I wasn't too inspired to troubleshoot the problem. I installed a starter booster relay and it worked fine. Then some time later while out driving there was a horrendous screeching noise. I shut off the engine and pulled over scratching my head. After a couple of minutes I tried starting it again. Afterall, the Raby engine was coming and the worst that could happen was I would have to be towed home. Miraculously the engine started and ran fine. I pulled away and things were fine for a short while. Then it happened again. I let the engine run and jumped out to try and isolate the noise but could not. Then the noise quit. I made it home without any problems determined to find the problem.

The problem became apparent the next time I tried to start the engine. The "clunk" in the trannie told me the starter was ruined. I pulled it off and discovered the starter and flywheel gears were ground off to nothing. Without further troubleshooting I blamed the booster relay since the problem only surfaced after its installation. I pulled the trannie, replaced the flywheel and starter, and drove the car only occasionally while awaiting my new engine, transmission, and just about everything else.

The new engine arrived, went in with all the other new stuff, including starter. There were some issues getting everything together but nothing mechanical. Plus, I replaced the ignition starter switch, just "in case."

Everything was fine until tonight. Shortly after starting the car I heard the screetch again. It wasn't quite as horrendous as with the other engine but I was shocked. Just to be sure I wasn't hearing things I fired it up again and as soon as the engine caught there was the noise.

This time my troubleshooting included disconnecting the yellow starter wire and starting the engine via the screwdriver method. Quiet, no screetching or grinding. This weekend I'll pull the starter and confirm it truly did engage the flywheel while running.

Has anyone ever experienced this problem? Any recommended solutions? I'm thinking of by-passing the solenoid wiring circuit and installing a 911-type starter button.

Just for kicks, here are the old and new engines:

Click to view attachment Click to view attachment

When you replaced the ignition switch, did you only replace the plastic part?

Yes.

Replace the whole assembly. I'll bet it solves the problem. Somebody here should have a good used one.

sounds like a ignition switch disassembly is in order. maybe a new one?

You're talking the metal key portion? I'll check my spare parts stash. I think I might already have another one. I'll just have to re-key the switch.

What about the seat belt warning relay? Perusing the wiring diagram tonight shows the yellow starter wire going to and from this unit. I think it's under the passenger seat in my '74.

It's a '74, even if you "forgot" to give us that information so we could give you a correct answer. Look at the wiring under the passenger seat. Clean it up. The Cap'n

Yeah, after sleeping on it and probably wrestling subconsciously with it all night I woke up certain it's the underseat wiring. At that point I even recalled sliding the passenger seat forward to reinstall the little piece of carpet behind it just before starting the car. Certainly there must be switched power somewhere in that jumble of wires and it wouldn't take much to get a short to the yellow starter wire, engaging the solenoid. Thanks Cap'n.

Found the problem, it was in the seat belt warning relay board under the passenger seat. The previous owner had removed the relays and installed a jumper across the starter wires. Another wire had come loose from the circuit and was laying against the starter circuit wire. This wire was switched 12-volts positive and engaged the solenoid when it bounced around and rested against the starter circuit wire. As the Cap'n suggested I removed the entire unit, permanently bonded and insulated the starter wires and isolated the other wires. Car starts fine now.

Would these same wires be a cause of a crank, but no start condition on a 75 L-Jet?

My car has been experiencing random no-crank episodes. The other night I parked it and when I tried to start it it did not crank. I did the natural thing and tapped on the starter solenoid. The car now cranks, but does not fire.

It almost sounds like the wiring under the passenger seat could be the whole cause of this as well?

Dunnow,

But I can testify that if you have a relay box plugged in, you are driving along, and you hit a bump, the engine can stop.

Quick slide the seat forward, nudge the box, and it would start running again.