Engine run-on problem

Jo Mama Commited Dubber

51 posts · joined Oct 2002 · 1 Jun 2003, 12:26 pm

#52693

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.

Stanley I guess the reward is in the doing of it

4,523 posts · joined Mar 2003 · 1 Jun 2003, 6:08 pm

#52748

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

vwguru Commited Dubber

62 posts · joined May 2003 · 1 Jun 2003, 6:27 pm

#52764

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.....

Peter Leonard Moderator Volatile

1,456 posts · joined Apr 2003 · 1 Jun 2003, 11:38 pm

#52886

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

let sleeping dubs lie

mnsKmobi Wolfsburg Wizard

589 posts · joined Aug 2002 · 2 Jun 2003, 9:00 am

#52916

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

Jo Mama Commited Dubber

51 posts · joined Oct 2002 · 2 Jun 2003, 2:39 pm

#52989

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.

KruizinKombi Seriously Obsessed Cyber Dubber

3,493 posts · joined Aug 2002 · 2 Jun 2003, 3:14 pm

#52999

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]

Kruizin Kol

Bizarre Moderator The artist formerly known as blue74l

12,787 posts · joined Aug 2002 · 2 Jun 2003, 3:55 pm

#53018

Jo Mama wrote: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)

I use to have a Progressive Weber that would run on IF not tuned properly.

BUT

on that carb and my IDFs you screw out to richen - in to lean.

Like - if you are say 3 turns out you have to put a bigger idle in there and then you will be less turns out

IF you have turned the screw all the way out then it eill be rich.

The mixture screw should be set at "lean best" and nowhere else.
Is this a Progressive or IDF Weber.?

I will be surprised if it is not a tune problem.
What jets are you running in the carb?

Futue te ipsum!!!

Jo Mama Commited Dubber

51 posts · joined Oct 2002 · 2 Jun 2003, 7:38 pm

#53078

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.

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 2 Jun 2003, 7:55 pm

#53087

I've just had the engine tuned

sounds like the place you had your car TUNED does not know what there doing.

Get the ignition timming right before you do anything else.

I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099

http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

Bizarre Moderator The artist formerly known as blue74l

12,787 posts · joined Aug 2002 · 2 Jun 2003, 7:56 pm

#53088

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

Futue te ipsum!!!

Peter Leonard Moderator Volatile

1,456 posts · joined Apr 2003 · 2 Jun 2003, 10:01 pm

#53168

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

let sleeping dubs lie

Peter Leonard Moderator Volatile

1,456 posts · joined Apr 2003 · 2 Jun 2003, 10:03 pm

#53169

which it did..

take the bugger back 😉

let sleeping dubs lie

Peter Leonard Moderator Volatile

1,456 posts · joined Apr 2003 · 2 Jun 2003, 10:06 pm

#53172

sorry am i running on here.. 😀

let sleeping dubs lie

Jo Mama Commited Dubber

51 posts · joined Oct 2002 · 3 Jun 2003, 2:31 pm

#53377

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.

Bizarre Moderator The artist formerly known as blue74l

12,787 posts · joined Aug 2002 · 3 Jun 2003, 2:49 pm

#53380

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?

Futue te ipsum!!!

kombi_kid Moderator Good Kid too many projects

124 posts · joined Aug 2002 · 3 Jun 2003, 5:35 pm

#53440

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

it aint just cool its aircool'd

Jo Mama Commited Dubber

51 posts · joined Oct 2002 · 3 Jun 2003, 6:32 pm

#53453

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.

Bizarre Moderator The artist formerly known as blue74l

12,787 posts · joined Aug 2002 · 3 Jun 2003, 8:37 pm

#53486

Sounds like an IDF then

either way...... 😀

welcome to the world of carb tuning!!

Futue te ipsum!!!

Bizarre Moderator The artist formerly known as blue74l

12,787 posts · joined Aug 2002 · 3 Jun 2003, 8:40 pm

#53489

kombi_kid wrote:hey
what about run on with kadrons???
cheers
rhys

follow the same rules

read up on AJ's site

www.lowbugget.com

there sre sections there on how to tune

Futue te ipsum!!!

Doug Pobjoy Learner Dubber

7 posts · joined May 2003 · 10 Jun 2003, 11:45 pm

#55850

KruizinKombi wrote: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]

KruizinKombi has nailed this question. Most after market carby's dont have the solenoid which cuts off the fuel supply when you turn off the ignition. In turn, when you get any carbon build up, the motor keeps kickin off the glow of the carbon using fuel from the float chamber to feed it. This can happen if your tuned right or not so dont freak out. Just do what Peter Leonard suggested about giving it a blat before switching it off or letting the clutch out as you turn it off. That will stop it.

This goes for Kadrons too Kombi Kid!

Good call KruisinKombi!:thumb

geodon Wolfsburg Wizard

478 posts · joined Aug 2002 · 12 Jun 2003, 4:30 am

#56211

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?).