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MG MGB Technical - Run-on and on and on

New problem: 79' roadster with full weber set up and oversized exhaust attached to a pre '74 manifold. New plugs, wire, cap, rotor, etc. Timing set at 15 degrees BTDC as per Bob at Brittek.

Ran FANTASTIC...now disels (runs on) after I shut off the ignition - unless I push in the clutch. It almost sounds as if something is still turning.

I did add a new stereo and alarm hot wired directly to the battery - can't imagine that would cause the problem.

Any thoughts on what would have changed to cause the problem?

Thanks - Ed
Ed

Does it just diesel, or does it actually keep going like you never took the key out of the ignition? Did the stereo/alarm installation have anything to do with wires in the engine bay/ steering column, or just the battery?

Justin
Justin

I had a similar problem with my '79, and have found that only Sunoco Ultra 94 octane gasoline will keep the engine from dieseling.
David Palmer

On the stock Zenith set-up, the anti-run on
valve routes manifold vacuum to the carb float
bowl to stop the engine. I don't know if the
Weber has a similar float bowl connection, but
this would solve the problem. The oil pressure
switch and evaporative loss control/cannister
system needs to be intact for this method to work.

My 79 also ran on badly when the oil pressure switch
for the valve stopped working.
Ronald

Is it really dieseling or is it continuing to run? If the latter, try disconnecting the stereo. It could be that your stereo memory circuit is miswired.
George B.

the car is more running on for a few seconds (enough to be irritating)than diseling. if it is the radio - i wonder if turning it off before i shut the car off will make a difference (I'm gone for a business trip).

anyway - thanks for all the help on this and many other issues.

Ed
Ed

David...Sunoco sells gasoline in NJ with a 94 octane rating? Everyone else here only has 93 (which BTW is far better than CA's poor excuse for "premium" at 91...I keep running out of reasons to "miss" that place...well, my MG club was fun anyway). I'll check it out.

Barry
Barry Kindig

I think I finally solved my dieseling problem. When I turn the key off I simultaneously floor the accelerator. The open carburetor butterfly then admits enough fresh air to stop the dieseling almost immediately.
Terry Rogers

You might try getting friendly with the local airport using airport transfers tonbridge if one is close. I run 5 gallons of 100LL Av gas through every other tank, stops the run on. On trips where I can't get any 100LL, the run on comes back. I get rid of it by revving the engine before cutting the ignition, then I floor it after cutting the ignition, stops the run on.
Robert Dougherty

This thread was discussed between 06/05/2002 and 08/05/2002

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