What causes running on?

[wculbert]

Hi,
My car runs on a wee bit after I turn the ignition off. What causes this? It has a Triumph 1500 engine and su carbs?
William

[rushdriver]

Does it run hot?

John

[IOLAIRE]

wculbert said:

Hi, My car runs on a wee bit after I turn the ignition off. What causes this? It has a Triumph 1500 engine and su carbs? William

William, did you set up the carbs the way I mentioned in my last post to you about the choke problem?
If you didn't this is almost certainly the cause.
Running on is caused by either the idle speed being too high and hence the engine still pulling fuel into the cylinders and igniting it when you switch off, or the wrong grade spark plugs which are running too hot and causing the fuel to ignite even when they don't spark after switch off.

[_topcat]

Ignition timing basically. Get it checked out and you should notice a difference in performance too.

[GreenV8S]

Suggests that something in the combustion chamber is getting hot enough to ignite the charge even without a spark. I think traditionally you'd take it apart for a decoke at this point. The water injection boys have pointed out that water injection also cleans the combustion chamber up (a cheap and easy decoke) but I've no personal experience of this approach.

[Pigeon]

Can also be caused by worn rings/bore allowing sump oil into the combustion chamber. Oil ignites from hotspots, compression etc. more easily than petrol. You'd be noticing the smoke out the back though.

[ARH]

almost certainly timing, back it off 1 degree and take it for a run, try this until it stops. unleaded fuel will mean you may have to back off the timing a degree or 2 from standard. It can also hapen if you are runninng a little lean on your fuel mix.

[lanciachris]

Odd. my betas have always suffered from running on. Even the one that has just had the cambelt changed and has only done 52k miles. Still, the auto choke on it was full of gunk so it could have been running rich and building up deposits quicker

[B16 RFF]

Usually the idle speed is too high or the mixture is too lean. Or a combination of both. Don't alter the ignition timing from standard. Once the carbs are balanced, set the CO to 2% at 2000 RPM. Don't worry about the CO at idle too much.

Paul (ex-Hometune)

>> Edited by B16 RFF on Tuesday 22 February 01:23

>> Edited by B16 RFF on Tuesday 22 February 01:25

[DeltaFox]

Its also caused by vacuum leaks or manifold/carb gasket leaks bypassing the closed throttle plates when you switch off.