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Old 09-02-2012, 02:55 PM
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Default still running on

I have an msd distributer and a msd box, I am getting run on.. I have a one wire alternator, so I did the ballist resistor install, and I still get the run on.. what other causes can this be? I have an electric fuel pump that is turned on by toggle not ignition switch, not sure if this can be part of the problem.. I run no electric fans.
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Old 09-02-2012, 07:20 PM
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Other causes are throttle blades open too far when setting idle speed. Idling too fast. (Close throttle blades and reset idle mixture -assuming Holley).
Bad fuel or octane too low. Hot spots in the combustion chamber that could be excessive carbon build up, a sharp edge or glowing spark plug ground strap from plugs that are "too hot" in heat range.

It's most likely too much throttle blade opening.
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Old 09-04-2012, 08:40 AM
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msdtech1955 msdtech1955 is offline
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any results?
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Old 10-02-2012, 12:26 PM
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I'd like to know the outcome.

I noticed that if I turn off my engine and then turn on the ignition a couple of seconds later I get a quick ignition run on for a split second.
I have BP8ES (quite cool plugs).
SS Blaster, 6A and stock Bosch cap.
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Old 10-09-2012, 09:47 AM
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Agree with BlackOut - I had the exact same issue with my 66 GTO which has a 389 Tripower. The center card throttle blades were not closing enough at shutoff, subsequently allowing fuel to enter into the manifold & cause run-on. We found that the idle mixture screw ports were undersized for my application and had to be opened up to a larger size, which then allowed me to adjust the settings properly & permitted the blades to close up, which did correct the problem.

Hope this helps & good luck!
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