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By Rono - 5 Years Ago
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I'm still having an issue with engine run-on after shutting the ignition off. This is an issue that started last year and I think we discussed this a while back, but I'm still trying to diagnose the problem. Weather my electric fan is running or not after killing the ignition, I still get run-on. With the car idling at 800 RPM with the vacuum connected the timing is at 12 degrees BTDC. I'm running dual Edlebrock 500 CFM carbs and a Comp Cam with a .489 lift. I believe the lobe centers are 108, but I can't seem to find my cam card. Without having access to a dyno, I'm really hesitant to mess with the fuel mixture. Metering Rods and Jets were initally set-up on a dyno by a factory trained Edelbrock tech and the car ran GREAT for years without this issue. Anyway, not sure where to go next with this. Any other ideas?
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By MoonShadow - 5 Years Ago
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It has to be getting power to the ignition from somewhere.
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By miker - 5 Years Ago
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Ron, is continuing to run, or is it dieseling like the early emission engines did?
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By crown55vic - 5 Years Ago
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Had a similar problem on a 70 Fairlane. Turned out to be the starter solenoid hanging enough to keep the ignition terminal hot but not engaging the starter. Rap on the solenoid and car would shut off. Cheap enough to try another solenoid.
Ben
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By Rono - 5 Years Ago
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Mike;
It's dieseling I guess but I didn't know there was a distinction between that and post ignition run-on.
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By MoonShadow - 5 Years Ago
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That is different. Will it idle any lower? Also is the engine high compression? What octane fuel are you running?
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By miker - 5 Years Ago
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Ron, I asked because you mentioned the fan and there’s been odd occasions where the fan turns into a generator and the engine runs momentarily on the feedback till it winds down.
Prior to the “emissions” engines problems, and the throttle stop solenoids, I saw that happen on lightly driven high compression motors. This is way back in 65-70. Particularly on my boss’s 396 in a half ton truck. (His father-in-law was the scrubrolet dealer. It was a COPO order with the high performance 396, not the truck motor). After a couple trips back to the dealership, an old time mechanic ran it at real high idle and poured a little water down the carb. Made a lot of steam, but also a lot of black smoke. Blew the carbon buildup out of the chambers, stopping the hot spots from causing the dieseling. He drove that like it was stolen, and nobody believed it was going to work, but it did.
I suspect you drive a lot like he did, but it’s cheap to try.
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By Rono - 5 Years Ago
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Thanks Guys! I usually run Ethanol Free 91 octane and the motor has ECZ-G heads with flat top pistons, so no high compression. If I try to idle the motor down more it runs erratic. Most of the time I take the car out my wife is with me. This means no power shifts. I'll take her out (by myself) and see if I can't blow out some carbon.
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By charliemccraney - 5 Years Ago
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Not idling well below 800rpm could be a clue depending on the other specs of the cam. .489" lift by itself doesn't tell us enough.
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By ian57tbird - 5 Years Ago
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I had the problem on a higher compression engine may years back. Only had to drop the idle about 50rpm and it went away.
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