I have a 1980 242 DL. I recently replaced the heater core and blower motor after two years of no heat. I get in my car, start it up and after running for about 20 minutes the starter begins to engage and make a horrible noise. I turn the key to the off position, pull the key out and the motor continues to run. I have replaced the ignition switch and ruled out the ingnition lock cylinder. I have been looking at some exposed wiring under the hood and trying to tape it up. Is there anything I am missing?

have seen exactly what you describe several times b4 and it has in my cases always come down engine wire harness

Oi! I was going to say that your ignition switch was probably sticking in between KP2 and KP3 like my 740 did, but I guess that's not the case!

I would carefully trace the wiring from your battery to starter and make sure it's intact. Then, rather than trying to trace the wiring for the starter from the ignition, I would run a completely new wire (encased in that black wiring tubing) to the starter.
I would also double check the way the wiring attaches to your ignition switch. I don't understand how the engine could stay running if you cut its spark and fuel supplies. By the way, how did you get the engine to stop running?

I would also point out that if this wasn't happening before you did the blower motor and heater core, there is a possibility you moved some wires into a position where they started shorting out or making contact with each other in the course of the job. Does everything else work right?

How did you rule out the ignition lock cylinder?

Oh, and congratulations on completing two of the worst (longest) jobs in the book. The car is not doing a good job of being grateful.

Good Luck!
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1990 740 Turbo, on its way to stock specs, maybe beyond

I ruled out the lock cylinder by disconnecting the ignition switch and starting it with a screw driver rather than the ignition key in the cylinder. I really do not know how it kept running after I removed the key, that is what made me think it was either the switch or the lock cylinder, but I replaced the switch and ruled out the cylinder. I looked in my haynes manual at the diagram of the charging system, after the wires from the switch go through the firewall they go to a connector that is mounted on the firewall directly behind the block. There is about 5 or 6 wires in this connector and all of them have exposed wire. I started taping them up.

The problem did not start till after I replaced the heater core and blower motor, I am inclined to agree with you that I most likely moved some wires around when I was putting everything back together. After doing a nightmare job like that, I am not about to give up on OLGA yet. She runs like a top.

Thanks,
Jacob

Ah, hey! Great! I'm glad you found the issue. Have you tried it since then?

Heat shrink tubing may go on the wires pretty easily and give you a lot less hassle than tape. You'd have to pull the connectors loose to get the tubing on them (You can't cut it, or it won't shrink in a circle).

Is the insulation rubbed off, or is it crumbling apart? If it's crumbling apart, the rest of those wires may not be far off from coming apart.

If you need to shut down the car because it won't turn off again, pulling the fuel pump fuse should do it, but it will take a while.

Good Luck! Hope you're enjoying the free-flowing air and heat now.
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1990 740 Turbo, on its way to stock specs, maybe beyond

The wires were the worst at the connector that is attached to the firewall behind the block. I taped all of them up and olga is running now and the starter is not engaging. Lets pray that she plays nice. Another question: since I bought the car the temp gauge has not worked. I have replaced the temp sensor and the wire going to it. The gauge goes all the way to hot as soon as you turn it on. I know that it is not running hot because I took it to a radiator shop and he tested it electronically. Do you have any suggestions? Someone had once told me that the voltage regulator in the alternator could cause this but I dont know.

Thanks,
Jacob

If the wire to the sensor touches ground it will read full hot at the gauge.The square blocks to the right of the speedo are a great place to install an aftermarket gauge,some of the digital ones are pretty cool.