Setting 34 PICT-3

[GavinHuart]

Hi chaps!

I thought the bus was idling a little high so I went to do the norm of adjusting the Fast Idle Adjusting screw (as I'd do on the 1200 in the bug). It then began to stutter during idle if not set high revs it initially was set to. I did a bit of research and came across this (it's quite a read so hereunder I've summated the article): http://www.vw-resource.com/34pict3.html#carb

"34 PICT-3 Carb setting:

1) Warm engine and turn off
2) Back off fast idle screw
3) Check the choke is open and set the fast idle screw clearance to 0.003 at the lowest point on the fast idle cam
4) Then turn the screw in precisely ½ a turn
5) Turn out the bypass screw (the larger screw) on the left of the carb 2-3 turns
6) Screw the volume control screw (the smaller one) in until it bottoms out – not too tight but closed
7) Now unscrew it exactly 2 ½ turns
8 ) Start engine again to make sure it’s fully warm (choke fully open)
9) Now set the idle with the bypass screw (the larger screw) by turning in or out (probably out) to set idling to fast idle (850 rpm)
10) Now go back to the volume control screw and adjust slowly to get the fastest, smoothest running idle speed (probably screwing out) Not more than a half a turn either in or out
11) Then turn the volume control screw IN very slowly until the revs drop buy 20-30 rpm (slightly leaner) – could be an adjustment as little as 1/8 turn in
12) Go back to the bypass screw (larger one) and reset idle speed to 850 rpm


…. done ☺"

I tried this after work yesterday and had no luck at all . By completing step 6 above (and having to screw the volume control screw in about 8-9 times for it to seat ) I moved onto step 7. I then tried step 8; starting it up, and that's where the poo started. She'd fire and then cut out almost immediately. I tried opening or closing the bypass screw either way in the hope that she'd idle but nope, no luck. In the end someone had to keep it ticking at the accelerator pedal to give me chance to get to the throttle at the engine so I could fiddle the screws to keep it going. The article stipulates that you are not to touch the fast idle screw once set to 0.003in which I've tried to stick to.
I've managed to get it to idle again by opening both the volume control screw and bypass screw almost all the way. I then closed each one one bit at a time (as each would drop the revs slightly) in a sort of "one-for-one tuning" method.

It seems to idle okay now and wasn't cutting out when I took it for a run last night but I've yet to start it from cold and see if it fires, which will be the true test.

What I don't like is that both the volume control screw and bypass screw are way off the settings given in the article above. Can anyone perhaps shed a little light?

Ta muchly!

[retrovan]

The most important part of the setting is at the start of the article.
As I stated the 1st time I placed this same article, is that most pictures, in the Repair manuals indicates the incorrect setting screw titles.

http://www.aircooledvwsa.co.za/viewtopi ... rb#p210011

The Big one is the "By Pass"

The small one is the"Volume Control"

As I too had a problem, I wound that most Books have these two screws mixed up.

When I found this article, Changed my Manual, and set the carb, as per each step, the car is perfect.

Herman

[GavinHuart]

Hi Herman,

That's the way I read it, and summated the article above, so I was doing what was required RE adjusting the bypass and volume control. The only thing is that mine wouldn't idle at all ...

[retrovan]

May I then recommend that you try carb cleaner spray prior to setting the carb, May work.......

May be blocked passages......

Best of luck

[GavinHuart]

Point taken and good suggestion

[fig]

I have written up how to set the idle on a 34PICT. You should be able to find it by searching.

[GavinHuart]

Hi fig!

I found this:

Fig wrote:

"On a 34PICT carb you should NOT use the idle screw on the throttle arm to adjust idle speed.

Use the volume control screw, which is the bigger of the two adjusting screws on the side of the carb, to adjust idle speed. As JamesD says, don't mess with the smaller screw (idle mixture) unless you really have to or unless you can smell that the idle mixture is over rich.

If you really have to adjust idle mixture, the rule of thumb is to seat the mixture screw then back it out 1.5 turns, then try adjusting idle with the volume control screw. If you can't find a steady idle, then screw the mixture screw IN a quarter turn at a time then try finding a steady idle with the volume control screw after each quarter turn. Ideally you should not mess with the idle mixture unless you have an exhaust gas analyser to hand."

... but you have it that the bigger adjusting screw is the volume control screw. Also, the smaller one is referred to as "idle mixture". The areticle I've posted has the volume control screw as the smaller of the two ...

[GavinHuart]

Ok, so now I've gotten to this:

Fig wrote:
"A couple more points to consider:

You called the small screw the volume control screw. In fact the small one is the mixture screw and the big one is the volume control screw. You described the right procedure, of seating the small (mixture) screw and backing it out 2.5 turns, then using the big (volume control) screw to adjust idle speed.

Once I have an engine idling at operating temperature using that method, I go back and reset the mixture by screwing the mixture screw in a quarter turn at a time and using my nose to tell when the exhaust smells right (ie, not too rich). This usually coincides with the instruction in the manual to screw the mixture screw in until the idle starts to stumble then back it out a quarter turn, but not necessarily.

In the past I have occasionally had carbs that refused to be adjusted. To overcome this I would start by seating the mixture screw and backing it out a quarter turn, then try the full range of adjustment of the volume screw, a quarter turn at a time (after first determining where it had been, by counting the number of turns to seat it). If I couldn't find a steady idle I would return the volume screw to where it was and back out the mixture screw another quarter turn and repeat. Eventually you will find a point where the engine will idle and you can then fine tune using your nose and the mixture screw, before finally setting the correct idle speed with the volume control screw.

I'm assuming, since you've checked the o-rings on the adjusting screws, that you have checked that the screws themselves are not damaged (which can in turn damage the soft seats inside the carb body)."

The bit in red is what I've tried to do, the only thing is that it wouldn't idle at all with the smaller screw (whetever it's called ) wound in either 2,5 or 1,5 coupled with multiple depths of adjustment of the larger screw. I could only get an idle with the smaller one way more than 2,5 turns out and the larger one close to that too....

[fig]

Sounds like you may have an air leak at the manifold, or possibly the carb itself (eg, worn throttle shaft). Have you removed and inspected the mixture screw (the small one)? If it's damaged it may be impossible to adjust correctly.

[GavinHuart]

I haven't taken the small adjusting screw out completely as I didn't know what to expect by doing so; teeeny o-rings being lost in the works or a spring firing out or generally stuffing it up altogether by fiddling too much. I'll do so though and have a look. "Quick Start" is also on the list . Can one take out the larger screw too? Perhaps a good soaking in carb cleaner?

[fig]

Yes, you can remove both screws. They should both have an o-ring at the top of the threads. The volume control screw is not so easy to damage, but the mixture screw is a long, thin, tapering thing that seats in an orifice in the carb body. Any damage to the needle part of the screw or where it seats will cause adjustment hassles.

[GavinHuart]

Right. I've tried EVERYTHING, and no luck.
What I did notice is that the small tapered adjusting screw was quite dirty and when cleaned up, had quite a bit of pitting and what looked like scour marks (perhaps someone tried to polish it up at some stage?). I cleaned the larger adjusting screw too. Both had the o-rings and the threads looked fine. By the by, I used carb cleaner to clean them. I then tried practically every combination of screw depths and could only get it to idle (very erratically) if the smaller screw was turned almost ALL the way out which is close to what it was set to initially. When making adjustments, and having to keep the engine from dying by yanking the throttle, I noticed fuel shooting out the right side of the carb where the one bush is on the throttle shaft. It also looks like it's leaking badly at the accelerator pump too so as far as I am concerned, this carb is tickets.

I'm in a bit of a situation as I need the bus running from next week (it barely idles at all now with all my fiddling). What would be the simplest fix? New carb (can you get new 34PICT-3's?) or reconditioned carb from somewhere?
Does anyone have, or can suggest where I could get one? I'd rather go this route than try and fix the old one at this stage because I'm sure this one is buggered right through.

Any help would be greatly appreciated

[boxerulez]

You do get the 34 pict3's new but there is also one on the forum right now in pretoria somewhere i think (Bratjie - R800) the new ones arent solex they are usually brosol, (Try midas for around R1600) I aint sure of the other places.

[retrovan]

You do get the 34 pict3's new but there is also one on the forum right now in pretoria somewhere i think (Bratjie - R800) the new ones arent solex they are usually brosol, (Try midas for around R1600) I aint sure of the other places.

Maybe even Goldwagen......

[forcecooled]

Hi Gavin
Give me a call - sure we can sort your problem out!
Bill Noble
072 110 2643