vacuum unit that closes the butterfly in the inlet to stop the engine on switchoffsticks so that the car will not stop. Is the vacuum unit faulty or does the fault lie elsewhere?:(

Hi there, welcome to briskoda.

What vacume unit/butterfly are you talking about exactly.

Is your car a petrol/diesel and which engine is it.

This will probably help people to diagnose your problem.

If it's a diesel and the car not stopping there is usually a solenoid which cuts fuel otherwise the car would keep running on. This can fail, but usually has a manual over-ride somewhere where you pull the contacts apart. This is usually located around the fuel pump assuming the skodas have them.

the engine is a 1.9TDIdiesel

The vacuum unit operates a butterfly valve that cuts off the air supply to stop the engine when the ignition is switched off.

On switching off the ignition the the vacuum unit is energised, closes the butterfly valve in the air inlet causing the engine to stop and not runon. After the engine stops the vacuum is released and the butterfly valve opens allowing the engine to be restarted when required.

There are other items connected to the vacuum unit which may allow the vacuum unit to be released.

If the vacuum unit does not release the engine will not start.

Its not its primary function though. The flap is for EGR operation.

The car should switch off anyway as the main power relay (109) looses its ignition live and that will shut down the engine management.

Very odd, any more info you can give is would be usefull. But the EGR flap is ECU controlled so having a look for fault codes would be a start, failing that if you remove the boost pipe is the flap sticking much?

On an old XUD engined BX I had exactly the same and it was the dieseling solenoid failing. This breaks the supply to the fuel pump which cuts fuel to the engine so that the engine can't run on.

As I said there might be a manual lever for this somewhere as otherwise the only way to stop the engine for me was to put the handbrake on, put it in 5th and lift off the clutch. (Not exactly elegant or safe, but was done until i found the lever).

If it is the part itself isn't too expensive if i remember, but getting it changed may cost you a bit depending on how deeply burried the solenoid is.

However since Lummox is the ex-skoda master tech and i havn't been fiddling with the Octy engine as of yet, I'd be going with his advice first

:( From the replies it seems that the the respondents have got hold of the wrong end of the stick.

The problem is not that the engine will not stop but that it will not start because the vacuum unit is still holding the butterfly valve closed. It can be released by hand.