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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
Posts: 3,733
Run-on/dieseling causes

Just lately, and only occasionally, when I shut her down (fully warmed up) she'll run-on for perhaps a scant second...as though one cyliner is still chugging along. No, I do not have the ignition delay relay hooked up, so the pumps and MSD ignition are both shut off at the same time with no timed ignition continuing to burn any remaining fuel.

I'm guessing that I have one injector pintel that's not staying closed when the fuel system pressure drops with the pumps off (i.e., residual pressure bleeding fuel through a faulty injector), and igniting within the cylinder. It would seem that either hot glowing carbon deposits or the tip of the hot spark plug is sufficient to ignite that small amount of fuel seeping past the injector.

Doing some research, I see where someone commented on reducing the plug gap to remedy the run-on. What's the logic with that approach? I run with a .040gap. The only logic I could see would be to run with a step colder plug.

Looks like I may have to pull and check the plugs, check all the injectors.... Fun fun.

Comments anyone?
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 09-22-2011, 08:26 AM
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