Electrical problem
1980 Other GMC Models V8 Four Wheel Drive Automatic
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I have a 1980 GMC K2500 that has all of a sudden developed some strange problems. I started it up and the alt gauge buired the needle past 18 volts. I then shut it off and now the truck will start and fire but not run. I assumed there was an electrical short and began to diagnose the problem. Upon trouble shooting I disconnected the starter wires and the alt wires from any contact with the rest of the positive system or ground. I began running tests with my DMM meter and found that in the run position, on the ignition switch. With the meter connected to the junction block and to ground there is a direct connection to ground. Is this correct in the wiring. If not, and I assume not. Is it possible that the ignition switch is the problem? I have checked all of the wiring under the hood to the fuse box and all is ok. How would I go about testing the ignition switch?

Thank you

I have a 1980 GMC K2500 that has all of a sudden developed some strange problems. I started it up and the alt gauge buired the needle past 18 volts. I then shut it off and now the truck will start and fire but not run. I don't get it please be specific is to the problem especially this one I then shut it off and now the truck will start and fire but not run are you talking about it won't move an inch?????????



Alternator gauge going whack- could be a problem with the internal voltage regulator.

As indicated in my previous posting the starter wires and the alt wires are not connected i.e. phisically disconnected for the purpose of this test.There is a contuninuty directly to ground thru the junctuion block. I this correct for the wiring? I have inspected all of the wiring under the hood to the fuse box connector and all is good. As far as start but no run goes the engine fires at the start position but as soon as I let the key go to effectively let the engine run. It the engine shuts off.

Its pointing towards a bad ignition switch test it out-when you let go the key from start the ignition circuit should power the ignition system but its not that's why it dies out. No power to coil