Electrical gremlin exorcized

[67since67]

This is for you Mitch...I will very much abbreviate the diagnosis trail.

In 2020 I finished up what amounted to an on-frame restoration on my '67 L34/M21 El Camino. With it's Southern CA heritage the bottom side is so clean I didn't feel the need to pull the body.

With some driving an issue developed where it would occasionally shut off and instantly restart with a twist of the key. Then it became more frequent but still elusive. Process of elimination ruled out the coil and distributor. Suspected were the ignition switch, the resistance wire in the new AAW engine harness, and fuse block connections. Then it lost ignition and fried the engine harness. Now diagnosis can get serious. Pulling the yellow wire off the outside post of the starter solenoid revealed that that post is grounded.

Opening the solenoid showed that the tang off the outer post was installed on the wrong side, back side of the contact disk and making intermittent grounding of the ignition circuit. When I would engage the starter the ground was interrupted and it would fire right up.

So a new solenoid on the original starter and a new AAW engine harness, problem solved. - Bill W

[dykstra]

Glad you figured it out Bill. I look forward to seeing this beautiful ElCo again! If I remember correctly this ElCo had AC too right?

[Lynn]

What brand was the solenoid?

[TimG]

Wow, what a nightmare to diagnose. I'm glad you discovered the issue.

[napa68]

I now feel better. I had the same problem with a 67 Corvette. I had the original starter rebuilt (including the original solenoid). Chased the same problem as you describe Bill. Even went so far as to replace the engine harness in the car figuring a wire got disturbed. In frustration, I went back thinking to my self......what changed? I shot gunned a solenoid at it and voila.......problem solved.

[Woj]

Wow Bill, that was one buried gremlin. Thanks for sharing. A buddy has a similar problem with his 64 GTO. I will pass this along. Thanks. Phil

[A12pilot]

That's some good sleuthing, Bill. Nice work!

Cheers
Dave

[Too Many Projects]

Yep, that's a new one for me. I've chased, and repaired, a lot of electrical issues in my years of repair and restoration, but never a defective solenoid.

In the seventies, if an intermittent starter engagement issue came up, I would disassemble the solenoids, carefully file the burned contacts, sand smooth and reassemble, all to save about $10 for a genuine GM replacement ... Apparently, I never put them together wrong.

[67since67]

Originally Posted by Lynn

What brand was the solenoid?

The solenoid has no identification on it, so can't answer that. I may go back in the folder and see if I can find an invoice.

[67since67]

Originally Posted by Woj

Wow Bill, that was one buried gremlin. Thanks for sharing. A buddy has a similar problem with his 64 GTO. I will pass this along. Thanks. Phil

Phil, have your friend place a hand on the engine harness immediately after it acts up. At one point I found the harness slightly warm but thought likely due to underhood heat. That may have been a clue??

Also, for a while I was driving around with a test light taped to a wiper arm and connected to the positive side of the coil. When it flashed off for a moment I knew it was either ignition voltage loss or grounding of the ignition circuit. But which and where??