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IGNITION SWITCH Problem or Hmmmmmm

Contributed By: Joe Sego

This is a tale of how an intermittent problem can cost you a fortune and make you crazy.

I bought my 79 Cherokee Chief in late summer 1996. It was sitting in a field for some time without a gas cap. The carb was all grunged up etc. After having it towed home. We put a Motorcraft 2100 (carb) on it off my 78 J-10. We changed fuel filters and got it running in no time. The previous owner told me they were selling it cause they couldn't keep it running. (hmmmm)

After letting it warm up I drove it and it seemed fine. I'm a happy guy. One day on a 10 mile trip to my mother's house, the engine died. It was raining heavily so I figured something got wet. Pulled off the road, waited a couple minutes and it fired right up. (hmmmm) I had forgot about this until late December with blowing snow and falling temperatures it died again. Pulled over, and started it right up. That night I decided to investigate further.

I decided maybe the new fuel filter was getting clogged up. Remembering the earlier incidence we changed the filter, plug wires, distributor cap, rotor. Took it out for a spin and died after 4 or 5 miles. Restart it and get it back home in the garage. At this point I thought it was fuel related and decided the gas tank must be in poor condition. We pull the tank, clean and flush it, blow out fuel and return lines and replace rubber fuel lines. The tank had a lot of rust and crude in it. Drive it, she dies after 5 or 6 miles. hmmmmm

At this point I decide the fuel pump must be clogged with all the junk from the tank. We replace the fuel pump. Drive it, about 7 miles and it dies. Wait a few minutes and starts right up. Next we rebuild the carb, no luck. Now I'm getting angry. I decide to let a real mechanic troubleshoot it. "What's she doing?" "Well I'm driving along and it's just like you turn off the key" "Heck, I'd replace all the electronics, "Ok" they replace the coil, the distributor trigger and brain box. Now it has to be fixed!!! WRONG. Drive it a total of 6 miles and it dies!!!! Now we're all stumped. Mike Baxter off the FSJ lists says hook a timing light to it and tape it to the hood with trigger taped the light as you drive. I do this and as it dies I notice no flash...hence, no spark. As I try to restart it I see with the key in the start position it's firing, as soon as I release the key to the run position it doesn't fire. Hmmmmm

I learn that most cars have two circuits, a start circuit and a run circuit. (why didn't that mechanic know this???) I check for coil voltage with key on....ZERO...I check coil voltage with engine cranking...12 V !!!! The coil is losing voltage in the run position. In the run position the coil should have 6 V +- (lower voltage keeps coil cooler) I hot wire the Chief and it starts and runs great! never stutters or dies. Studying the wiring diagrams it all points to the ignition switch. $12 and a trip to NAPA and all is well. I'm a happy guy.

Morale- I never gave up...I replaced almost everything. The previous owner sold me a great truck for $300 because of a $12 ignition switch. btw, the ignition switch is NOT the thing you pt the key in, it's a ceramic switch mounted on the lower steering column. yeah I know, a REAL mechanic would have found that in no time. Well I say a REAL mechanic missed it too. After telling this story several times I learn that faulty ignition switches are a common problem with older vehicles. They can be cleaned, but for $12, why bother?

So, if you experience an intermittent problem such as I did, check that coil voltage post haste!!

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