This page is a prototype for a set of pages of generic advice for the owners of Classic cars, "Classic Car Problems". They are intended to provide suggestions on how to solve problems, and how to carry out procedures and projects concerned with the ownership, maintenance and restoration of those cars.

Running-on

Running-on occurs when, after turning off the ignition key, the engine continues to run. It is due to “dieseling”, where fuel mixture auto-ignites, like a diesel engine that runs without electric ignition, usually because of excessive temperature in the combustion chamber. This may be caused by

Weak mixture
Excess advance
Poor cooling

Structural

Sediment in block
Unequal compressions
Cooling system faulty, sedimented. Use water wetter?
Grossly worn piston rings. Oil fumes sucked up into bores and ignited.

Adjustable

Carbs

Mixture too weak
Worn jets/needles
Worn/maladjusted butterflies
Unbalanced carbs
Idle speed too high
Intake air hot

Ignition

Excess advance

OR

Excess retard( may be due to mismatch of UK with US retard parts)
Plugs too hot Stnd = BP6ES, Next colder BP7ES. BP8ES should not be a problem
Failing diode in ignition circuit allows alternator to power ignition despite ignition 'off'.

Valves

Cam timing
Tappets tight

Others

Use max. octane fuel possible