Hello Friends,

I'm hoping one of you may enlighten me on why my engine rons on after switching off. It happens every time, with some occasions running on for over 15 sec. Even after a 5 min drive.

Details that may be of interest:
-Baja
-Non stock engine (not sure how big, around the 2ltr mark)
-Electric fuel pump
-Single Port
-Weber carb (double barrel)
-Premium fuel (occasionaly mixed with unleaded)

I've just had the engine tuned, and have installed a fuel regulator inbetween the the fuel pump and the carb. The fuel reg has a dial of 1 to 5 on it. Even with the dial on 1 I still get run-on. Where is the fuel comming from and what is sparking it?
The carb is tuned to be as lean as it should be (assuming that my model carb requires the mixure screws to screw out for a leaner mixture)

Any insight would help.

Thank you,

Nick.

Only cause for running on or pre-ignition that I know of are mixture or timing.

running on can be caused from a few things. your timing being to far advanced, fuel still getting into your engine from your float level being to high or a hole in your float which then doesnt stop fuel gettin in to your carb when it shouldnt, your needle and seat sticking. or to much carbon build up in the head; which when the carbon heats up it turns red and acts like a spark plug.....

aaaack
15 seconds of your engine misfiring/running on is doing it nooo good...
the carbon build up is likely the reason.. like a glow plug..unfortunately it's unlikely to be running on in sequence... so every time it goes bang! it's gonna be pummelling the guano outta your engine. easy way to stop it from running on is plant your foot just as your turn the key off: and stop the engine by engaging the clutch at the same time. the cool fuel will stop it, as will first gear. This works for me ... in fact if you get used to the timing, it'll feel exactly the same as everyday turning it off, but it takes a little skill, so you can smile every time you do it. I reckon what's doing it is the misfiring, turning the engine enough to suck a bit more petch thru and perpetuate the cycle. if you find an easier way, let me know too, but the shot of petch'n'clutch trick has been working for me for years.

oh, yeah, and try running some redex thru it. :thumb

My kombi developed the nasty habit of running on after long trips. Cured it by setting the valves. They were all tight.

Peter,
I had a idea of what might be sparking the fuel but I just found it strange that there was still enough fuel to run the engine.

Thankyou everyone for your input.

Nick.

My kombi has a solenoid in the idle circuit which prevents the engine running on when the ignition is cut. Any car will run-on if things aren't right (ie. timing, heat) but air-cooled VWs tend to do it anyway, which is why many of them are fitted with idle circuit solenoids as standard. Maybe you could find a way to fit one to your Weber?

Ps. It is running-on using the fuel in the float chamber.

[Edited on 2-6-2003 by KruizinKombi]

Its a non progressive weber. I'm not sure what type though. I've got a feeling you may be right though because it didnt always run on. Is there a way to tell if rich is in or out?

Nick.

Out is definitely rich

You screw it in to kill a cylinder by shutting off the fuel

Go to the Redline Weber site and pick which carb is yours.

http://www.redlineweber.com/html/Tech/Table_of_contents.htm 

follow the instructions and you will be able to tune from there

I'm assuming it was tuned properly here... any worries.. take it back, that is if the problem occurred after they 'tuned' it...
:alien

which it did..

take the bugger back

sorry am i running on here..

This is why I get confused. You guys are telling me what I think correct - screwing out is rich. But this is what is says on the Redline Weber site http://www.redlineweber.com/html/Tech/idf_adjustment_controls.htm 



"If your mixture screw is out more than one turn like 11/2 turns then your idle jet is too lean, go up one half size on the Idle jet.

If you mixture screw is not out one full turn, something like only 1/2 turn out from seated then your Idle jet is too rich, go down one half size on the idle jet. "

Is there a way to make sure what way is which?

Thanks,

Nick.

Nick

"If your mixture screw is out more than one turn like 11/2 turns then your idle jet is too lean, go up one half size on the Idle jet. "

What is is saying is - for arguments sake you have a 55 idle jet in there and it is 3 turns out for "best lean"
Screwing it in kills the circuit / cuts off the fuel / leans it out.
To RICHEN up the circuit you have to screw it out 3 turns till it is running best.

So you take out the 55 and put in a 60. You have RICHENED up the circuit. You will now find that the mixture screw only needs to be 1 1/2 turns out for "lean best"

You shouldnt have the mixture screw any place other than "lean best" where the circuit runs best for the least anount of petrol.

Screw in kills the cylinder. On a single carb you will kill the engine if you screw it in too far. It has stopped ALL the petrol. By screwing it out you are richening up the circuit (from nothing) until the cylinder is running LEAN BEST.
Any more than this and you are OVER FEEDING the circuit (and probabally why you are running on)

You totally confused now.

Go and tell me how many turns out you are for LEAN BEST.
And tell me what size jets you are running.

We WILL get this motor to stop running on.
Jetting is hard to under stand - then all of a sudden it clicks.

Have you worked out what model carb it is yet?

hey
what about run on with kadrons???
cheers
rhys

blue74l,

Thank you for your help. I was getting "go up one half size on the Idle jet." confused with turning the idle mixture screw. This morning I re-tuned the carb and at the moment, both idle mixture screws are roughly 1 1/2 turns out. My engine didnt run on when I got to work, and it didnt run on when I got back. A fdew more drives will tell me if its cured.

My carb is a non progressive weber. Its on back the front with all the screws facing the fan housing. This is because the fuel intake is on the left. I'll have to find out the details on the weekend.

Thanks,

Nick.

Sounds like an IDF then

either way......

welcome to the world of carb tuning!!

Quote:

Originally posted by KruizinKombi My kombi has a solenoid in the idle circuit which prevents the engine running on when the ignition is cut. Any car will run-on if things aren't right (ie. timing, heat) but air-cooled VWs tend to do it anyway, which is why many of them are fitted with idle circuit solenoids as standard. Maybe you could find a way to fit one to your Weber? Ps. It is running-on using the fuel in the float chamber. [Edited on 2-6-2003 by KruizinKombi]

If you are still in trouble after following the above advice you may consider trying a "dump valve". These are electro-magnetic valves open to the atmosphere connected to the intake manifold BELOW the carb. When energised by the ign on circuit, they close. When the ign is turned off, they open but this time the air is sucked in minus petrol and so the eng doesn't run on. I used one (albeit on a heavily modified Sprite) years ago from a Ford Escort- it cost around $20- & connected it to the vacuum take-off. (if it's there on your vehicle?).