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

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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

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  • 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

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Carbs

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

Ignition

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  • 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

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  • Cam timing
  • Tappets tight

Others

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  • Use max. octane fuel possible