Continued running after switching off ignition

[the edmundator]

(For info this refers to a 1989 1.8 GT with a Pierburg carb.)

You'll have to excuse my ignorance, I'm not certain if this is an electrical or fueling issue (although clearly I've plumped for electrical).

My GT continues to run (albeit roughly) after the ignition has been switched off, until it eventually stops of its own accord. I've had this happen before with other cars, so I imagine there's something relatively common that causes this, but I don't know what it is.

Coincidentally (and possibly entirely unrelated) the battery goes flat fairly quickly if the car is left to its own devices - there is no radio or alarm fitted.

All advice greatly appreciated.

[Village Idiots]

Car carrying on running with ignition turned off is known as 'dieseling'. I had a Renault which did this and the only way to stop the engine was to deliberately stall it! It's caused by a build up of carbon in the combustion chamber which glows red hot and continues to ignite the fuel. You might be able to cure it by using some cylinder head cleaner in through the induction system. Or it might simply be the ignition switch is not switching off properly.

[go-for-it1]

Agree with VI re carbon build up, also consider that the ignition timing too far retarded causes run on but the most common reason with a Pierburg is the black electrical gubbins at the back left side of the carb (as you look at the engine from the front). It is an idle over run valve which I think breaks vacuum in the carb causing the fuel to stop being drawn in to the engine when you switch the ignition off. There's a guy on Mk1 Golf owners club forum called RubJonny who has put an excellent sticky about Pierburg checks in the big block carb engines section which may help. Paste the link below into your browser. Thank you RubJonny, hope I am not breaching any rules by linking it here!
Rob
http://www.vwgolfmk1.org.uk/modules.php ... ic&t=61457

[Sean]

but the most common reason with a Pierburg is the black electrical gubbins at the back left side of the carb (as you look at the engine from the front). It is an idle over run valve which I think breaks vacuum in the carb causing the fuel to stop being drawn in to the engine when you switch the ignition off.

This was my first thought when I read the original post. My mk1 golf cab had exactly the same symtoms. I believe it was the same engine 1.8 with pierberg 2e2 carb as your GT2.

[Nate]

can be caused by fueling or ignition problems. 1st check is that the timing is set up right