48IDA dripping fuel out acc. jet when idleing - why?

[Rasser]

Hi

I discovered a slight problem this weekend, and I can´t figure out how this is happening.

I have a pair of 48´s mounted and me and a friend were out driving. When we returned I left the car idleing, and we took a look at the engine, that´s when we discovered that one of the carbs was dripping a little bit off fuel down the two throats. It was only a little bit, but enough to make the idle a little more rough(no rpm drop, just a little rougher). You could see equal amount of fuel dripping from both acc. jets on the same carb.
Fuel pressure was ok, and the carbs were not hot at all.
I first thought that the needle valve might be leaking, the float was punctured or excessive fuel pressure. But that would force fuel out the mains (aux. vent) instead - right?

could it be the acc. pump piston that is jumping up and down a little, causing fuel to be pumped out the jets? and what could cause this - spring to soft, or not fitted right?

It´s the new IDA´s with push in acc. pump jets (not screw in), and they have brand new o-rings, and they are all correctly fitted.

Anyone have any idea what is happening, or have anyone ever experienced the same

[Rasser]

?

[Bruce]

could it be the acc. pump piston that is jumping up and down a little, causing fuel to be pumped out the jets? 

That's exactly what's happening.  The acc pump lever is right on the base of the cam and the pulses of the intake are causing the throttle to flutter slightly.  Enough to push fuel out the pump nozzles.
Advance your idle timing.

[Petter Carlberg]

I think you are just a little out of synch.

[BeetleBug]

I think you are just a little out of synch.

Probably... he is Danish

 

[Rasser]

  hahahaha 

I don´t think the carbs are out of sync, because this was just done prior to the drive. But I will check if the dripping stops if I hold the throttle steady at the acc. cam lobe.
But I will check if they are still synced, something could have gone wrong when it was done last.

Thanks for the input
Will let you know when I find a solution.

[Jason Foster]

could also be intake leak.

[Rasser]

could also be intake leak.

How could intake leak cause this (I´m guessing you mean between carbs/manifold or manifold/heads)?

It responds well to idle mixture adjustments, so I don´t think it has an intake leak.


Maybe I should mention that it doesn´t drip all the time, I have only seen it dripping a few times, and couldn´t figure out why.

I´m leaning towards the acc. pump piston movement idea....  but hopefully tomorrow I will have time to look into the problem. But still all input is appreciated, it makes my work so much easier.

[Ben67]

Try disconnecting your linkage, set idle of both carbs, re-adjust and re-connect linkage.
Could be the carb that is dripping is adjusted just a hair off idle causing the drip.
Or the throttle shaft is bent

[Rasser]

Try disconnecting your linkage, set idle of both carbs, re-adjust and re-connect linkage.
Could be the carb that is dripping is adjusted just a hair off idle causing the drip.
Or the throttle shaft is bent

Throttle shaft is not bent, I have measured each carb with my sync tester and they are all pretty much the same.
And it´s dripping down BOTH throats on the same carb.
Could be that one carb has the throttle just slightly more open, but I have just adjusted the carbs just like you described - but offcourse I could have made a mistake.

[Torben Alstrup]

Back the acc. pump cam up a hairswith.
T

[Rasser]

Back the acc. pump cam up a hairswith.
T

You can´t adjust the acc.pump cam, but you can bend the lever that connects to the acc. pump piston - but that won´t help anything since this only moves the piston a bit up (or down, depends which way you bend the tab). Either way it won´t have any effect.

I think what caused it was rattleing from the throttle linkage, this transformed into the throttle shaft and then the acc. pump piston, which then vibrated and pumped a little bit fuel out. Estimated guess.

They carbs were in perfect sync, And I cleaned all the acc. pump cam/lever etc.
I could not see any fuel dripping out afterwards- but I will watch in the future, and if I see it again, then I can try to "lock" the throttle or acc pump lever, and see if the problem disappears. Perhaps some dirt got caught underneath the carb, causing it to jump a little - who knows....

[folkevogn]

You can´t adjust the acc.pump cam, but you can bend the lever that connects to the acc. pump piston - but that won´t help anything since this only moves the piston a bit up (or down, depends which way you bend the tab). Either way it won´t have any effect.

I think what caused it was rattleing from the throttle linkage, this transformed into the throttle shaft and then the acc. pump piston, which then vibrated and pumped a little bit fuel out. Estimated guess.

I think your right, I`ve had the same problem. I ended up making some thin sleeves(about 1 cm long) that I slided on the acc. pump stem to make a little spacing between the acc. pump cam and the stem when idling. This stops the fuel leak. The butterflies moves about 3mm before the acc. pump piston starts moving. This works perfect and you will not feel any difference in engine performance.

[RMS Boxer Service]

Perhaps some dirt got caught underneath the carb, causing it to jump a little - who knows....

Dirt on your engine? Never seen it and doubt I ever will see dirt on ypur car or engine

/Rolf

[Ohio Tom (DdK)]

don't forget that your symptoms are exactly the dreded "worn out throttle shaft bore" syndrome.
What happens is that the shaft (over time) egg shape the center holes in the carb body.
this allows the throttle shaft to vibrate up and down during idle, thus pumping the accel pump.

Check for wear on these holes. If that's the case ,then you can get creative to stop it like described above.
Or, you can have the carb bodies re-bushed. Not many folks do this (ACE does).

[Bruce]

Easiest thing to do is this:

Advance your idle timing.

[Rasser]

could it be the acc. pump piston that is jumping up and down a little, causing fuel to be pumped out the jets? 

That's exactly what's happening.  The acc pump lever is right on the base of the cam and the pulses of the intake are causing the throttle to flutter slightly.  Enough to push fuel out the pump nozzles.
Advance your idle timing.

I understand what you are trying to do when you adjust the idle timing, but this just sounds like a bad idea - remember the problem was only on one carb!
I also tested to see if it the throttle would fluffer slightly, and it didn´t (tried to hold fix it, and it didn´t cure the problem)

But I solved the problem today. I finally had some time to look into the problem, and I found out that when dripping at idle, I could push the pump/piston lever just a little bit down towards the manifold (fingers in between carb bodies), and this would stop the drip. I also tried to fix/hold the throttle, to see if this would stop the drip - but no. Needless to say I bent the arm just a little, and problem disappeared.

It was an easy fix afterall.

Thanks everyone for the input!

[Torben Alstrup]

Back the acc. pump cam up a hairswith.
T

What-did-I-tellya ! OK not quite, but same result.
T

[Rasser]

Back the acc. pump cam up a hairswith.
T

What-did-I-tellya ! OK not quite, but same result.
T

Same result yes (it stopped dripping).   But didn´t back it (the opposite), and it wasn´t the cam. But yes it had something to do with the acc. pump ;-)

[Rasser]

ok problem is still here, last time I only thought it had disappeared      But today when I was trying to check my idle mixture (adjusting idlescrews), I couldn´t adjust i porperly on one carb - turned out it was still dripping a little fuel.

I found out that it indeed is pulses from the intake that is causing the throttle to "rattle" slightly, just as some of you suggested. I can feel the acc. cam/throttle shaft rattle with the intake pulses - and I can´t stop the rattling by holding the cam by hand, the pulses on the throttle are to strong.

I will either have to get creative and sleeve the acc. pumprod with rubber or something similar, in order to stop it (as suggested), or try to advance the idle timing and see if this helps weaken the intake-pulses (as bruce suggested).

But why is it only on one carb that it makes these strong intake pulses? (this it getting me worried). I wil check valveadjustement as soon as engine has cooled down, but they should be fine. What else could be wrong - a loose valveseat?, or is it really the cam profile that causes it (only on one carb..)?

Thanks
Rasmus

[Bruce]

..... or try to advance the idle timing and see if this helps weaken the intake-pulses (as bruce suggested).

That's not how it works.  Advancing your idle timing makes your idle speed higher.  Then to get the idle speed back down to where you want it, you close the throttle a bit, withdrawing the pump cam from the pump lever.  When the lever isn't hard against the cam, the nozzles don't drip when the throttle flutters due to the intake pulses.

What's your idle timing?

[Rasser]

Idle timing is now 7-8 degree BTDC,  24degrees totaladvance, ending at 31-32degree. Advance starts at 1200rpm.

[DKK Ted]

When you sync you carbs do you disconnect one arm off a carb? Try disconnecting the arm off the carb that is leaking, if it stops it's you linkage not synced, if it's sync slightly off in your linkage, just get a soft hammer and tap the arm on the linkage one way or the other depending on the angle of the arm. Had same problem, learned this trick from somebody that has been VW's longer than I can think. Maybe this is the problem, good luck.

[Rasser]

When you sync you carbs do you disconnect one arm off a carb? Try disconnecting the arm off the carb that is leaking, if it stops it's you linkage not synced, if it's sync slightly off in your linkage, just get a soft hammer and tap the arm on the linkage one way or the other depending on the angle of the arm. Had same problem, learned this trick from somebody that has been VW's longer than I can think. Maybe this is the problem, good luck.

I know what you mean, but sadly this isn´my problem.
Thanks

[Bruce]

Idle timing is now 7-8 degree BTDC,  24degrees totaladvance, ending at 31-32degree. Advance starts at 1200rpm.

Your idle timing is fairly retarded.  I'd go to 10-11º.  You can test this by setting your timing there and closing the throttles to see if the dripping stops.
What distributor do you have?  What is your target idle speed?

[Rasser]

Idle timing is now 7-8 degree BTDC,  24degrees totaladvance, ending at 31-32degree. Advance starts at 1200rpm.

Your idle timing is fairly retarded.  I'd go to 10-11º.  You can test this by setting your timing there and closing the throttles to see if the dripping stops.
What distributor do you have?  What is your target idle speed?

It´s a 009 dist which i modified a bit.  I have actually thought about setting it at 10-12 degree at idle, and then only have 20 degrees total advance. It´s fairly easy to alter the total advance in that dist. so maybe I should try that. 
either way, as you say I can just try to adjust the ide timing to 10-11 degrees, and readjust idle on carbs - and then see what that does.
I just never thought of it as a timing issue - but will try and see what difference the idle timing does.


thanks for your help

[Bruce]

What idle speed are you shooting for?  If you want 1100rpm, drop it to 900.  That alone will help the dripping.