Stays running
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Junior User
Joined: Sep 2006
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From: Grantville, PA
Stays running
Another question from me. I seem to be unable to adjust the carb right on my truck. After I turn it off its stays running like dieseling until I choke it out. Its a 650 Holley double pumper on a 390FE. I'm no expert on Holleys but I followed all the instructions and it still isn't right. Does this sound like the carb? I haven't changed anything else and I do not remember it doing this before. Any help is appreciated.
Postmaster
Joined: Nov 2001
Posts: 3,351
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From: Escondido, CA
I'll say check the ignition switch for a bad selector if the timing isn't out of whack. Even if you were dumping fuel down the carb while running and shut off the ignition switch it would die. Fuel doesn't create it's own spark to fire the mixture. Except in rare occasions where you have a hot spot in the cumbustion chamber and high compression, like a diesel.
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Junior User
Joined: Sep 2006
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From: Grantville, PA
I've been meaning to check the timing I just thought it was wierd that it did not start doing this until I rebuilt and reinstalled the carb. The ignition switch is all messed up the PO had replaced part of it with some universal switch so it is really loose and hard to switch if you know what I mean. Thanks guys!
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Joined: Jan 2004
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From: denver
My original 2bll autolite carb ('73 f-100, 390ci) had an electric solenoid that was used to adjust the idle. The solenoid was hooked up to the ignition+ so that it was energized whenever the truck was running. When the truck was turned off, the solenoid allowed the throttle blades to close completely. Before I knew the pupose of the solenoid, I had adjusted the idle with the throttle stop, where the throttle stayed open after the ignition was off, and it dieseled horribly. So, these solenoids are available for most carburators (may be listed as an A/C step up solenoid), or you could modify an junkyard solenoid.
After adjusting your timing, you could also try a number of things. There are products available to clean the carbon out of the combustion chambers, and you could run a colder spark plug. You might be able to fix it with a leaner idle mixture also. I also got in the bad habit of shutting the truck of while it was in drive.
After adjusting your timing, you could also try a number of things. There are products available to clean the carbon out of the combustion chambers, and you could run a colder spark plug. You might be able to fix it with a leaner idle mixture also. I also got in the bad habit of shutting the truck of while it was in drive.
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Junior User
Joined: Sep 2006
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From: Grantville, PA
Well I set the timing to a little under 10 with the vacuum advance disconnected but not blocked. It goes to 10 with the vaccum connected. The truck seems a lot more responsive but it still ran when I shut it off. I'll try leaning out the carb more. Thanks for all your suggestions 
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Junior User
Joined: Sep 2006
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From: Grantville, PA
Idle is around 900 I can't get it to go any lower. I adjust the screw all the way out and that is where it sits. I let the throttle cable mount have some slack and it doesn't go any lower. I don't know if my return spring is too weak or worn out or what.
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Postmaster
Joined: Nov 2001
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From: Escondido, CA
You can buy a new ignition switch and cylinder from local auto parts stores for less then $35. That should stop the engine from doing what it is if the switch is at fault which it does sound like. Universal switches aren't the best when it comes to functioning as your describing. You can troubleshoot the switch by attaching a jumper from the battery terminal to the "I" and then jumping from "I" to "S" to start it. Take the jumper off "I" to simulate an ignition switch. Then you can rule out the switch or identify that as in deed the problem.
Logistics Pro
Joined: Jun 2003
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Do you have mechanical or electric choke?
There is an idle screw on the choke cam (for high idle) also that may need adjusting.
Generally "dieseling" or "running on" is from the throttle plates being open too far or vacuum leaks.
There is an idle screw on the choke cam (for high idle) also that may need adjusting.
Generally "dieseling" or "running on" is from the throttle plates being open too far or vacuum leaks.
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Junior User
Joined: Sep 2006
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From: Grantville, PA
Well I "fixed" my problem. I swapped the holley for an edlelbrock 600 and it runs like a normal car now haha. No more dieseling or hard starts. I haven't tuned it yet but it seems to run pretty good. Thanks again for all your help guys. Now I can start fixing other stuff.