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Thu Nov 05, 2009 4:29 pm

Here's the scoop on my '73 STD. 34Pict-3 Carb.

I can get it to start up, idle, run, choke is working correctly. After I let it warm up, I"ll drive it to work (about 5-6 miles). When I start getting close to work/home, when I let off the gas, it stalls out. It's like the choke is opening too much and the accelerator isn't open enough. I've adjusted the accelerator screw to where it's almost screwed all the way in. Could it be a problem with my choke, or is the carb too rich or too lean?

Or could it even be the fuel filter getting clogged and when the choke is open it's only getting enough fuel when i push in the pedal, and not when I let up?

Dies in gear, or in neutral after I've been running it and the choke opens up.

Thu Nov 05, 2009 4:39 pm

Try adjusting it to these specs first:

http://www.youtube.com/watch?v=KWdZSr7x81w

If that doesn't solve it, a tune up may be needed as may a repair of a vacuum leak.

Good luck!

Thu Nov 05, 2009 4:49 pm

The PO had the choke held by bailing wire to the 2nd step, which when in that position, it runs smoothly. But since I rewired the choke, I removed the wire to try to make things work right. Would that be a sign of a tune, vacuum leak or carb issues?

There's always something :shock:

Thu Nov 05, 2009 5:26 pm

That "fix" sounds like the added fuel by wiring up the choke compensated for extra air getting in, like from a vacuum leak.

Thu Nov 05, 2009 5:43 pm

I'm new to VW's and working on engines.

Where (in dumby terms) would be the places to start and continue and then keep continuing looking for vacuum leaks?

Thu Nov 05, 2009 5:58 pm

learningbymistake wrote: Here's the scoop on my '73 STD. 34Pict-3 Carb.

I can get it to start up, idle, run, choke is working correctly. After I let it warm up, I"ll drive it to work (about 5-6 miles). When I start getting close to work/home, when I let off the gas, it stalls out. It's like the choke is opening too much and the accelerator isn't open enough. I've adjusted the accelerator screw to where it's almost screwed all the way in. Could it be a problem with my choke, or is the carb too rich or too lean?

Or could it even be the fuel filter getting clogged and when the choke is open it's only getting enough fuel when i push in the pedal, and not when I let up?

Dies in gear, or in neutral after I've been running it and the choke opens up.

This thread might help... it's helped many others.

http://www.thesamba.com/vw/forum/viewtopic.php?t=56411

If you mean the screw on the throttle arm then that's a big mistake on a 34 pict 3.

Thu Nov 05, 2009 6:18 pm

yeah... the throttle valve adjustment screw.

Thats what you get for listening to tank mechanics...

Thu Nov 05, 2009 6:30 pm

On the "earlier" VW model carbs that was where you set the idle. Starting with the later carbs around 70 things changed and you don't use that screw to adjust the final idle at all. And screwing it in to try and keep the engine idling better just makes the carb function even worse and impossible to tune correctly.

Thu Nov 05, 2009 6:41 pm

SO back it out to about half-way, then follow the steps to set the carb straight, and make sure the choke it set properly, and ensure there are no vacuum leaks. If all that checks out, then go for the tune-up?

Thu Nov 05, 2009 7:36 pm

learningbymistake wrote: SO back it out to about half-way, then follow the steps to set the carb straight, and make sure the choke it set properly, and ensure there are no vacuum leaks. If all that checks out, then go for the tune-up?

Back it out all the way until it does not touch the last step on the cam ( choke warm/position) then screw it in until it just touches and 1/2 turn more.

Read in the thread I linked what I wrote about checking the solenoid and the "idle pilot jet". I bet the pilot jet either has some debris clogging the hole in the end of it or needs to be set in the sweet spot.

Set the big air screw out 2.5 turns, and the small mixture screw out 2.5 turns for a baseline setting.

Then you can try tuning it further from there when it warms up completely and you have it idling better.

Sun Nov 08, 2009 9:29 pm

I haven't tried anything yet with the bug, just been sitting, but I've been thinking a lot about it while doing other things around the house and with the wife.

When it's cold, the choke is closed off, which is allowing more fuel to make it idle. When I drive it, it's fine while I'm accelerating, and when the choke warms up, it allows more air in and less fuel.

Since it's dying when I let up off the gas, would that mean there's a good chance it's the fuel filter or fuel pump going out, not pushing enough fuel in to the carb to allow it to idle, and only enough when I'm pushing in the accelerator pedal?

Might go and pick up a couple new fuel filters tomorrow, try that out, and then mess with the choke adjustment and carb.

Mon Nov 09, 2009 4:26 pm

If you're worried about the fuel filter and don't know when it was last replaced, go ahead and replace it. It's cheap insurance.

Sounds more and more like a vacuum leak. While the choke is ON and while you are accelerating the leak would be a small percentage if the air entering into the intake, so it is less noticeable. Once the choke is OFF and you are idling the leak adds too much air to the mixture reaching the cylinders. Thus makes the mixture lean.

You can test/check this a couple ways.

While the engine is idling, cover the carb opening with your hand. You want to block off around 90% of the opening. This should cut off some of the air entering the carb. This should normally begin stalling your engine because it doesn't have enough air and the mixture will go rich. But if you have a vacuum leak you will balance the mixture and the engine should run better!

To find your leak... take a spray can of carb cleaner or WD-40 and with the engine idling, spray around all gaskets and connections for the carb/intake. Pay special attention to the intake boots and carb throttle shaft. When you spray the leak it will momentarily close the leak and add more fuel (carb cleaner) to the mixture. The engine idle should change (up or down).

Mon Nov 09, 2009 4:56 pm

I've taken my carb off to be able to get a good look at it. took the stationary idle pilot jet (or so I think) off to check for debris in the holes, nothing there. Took the screws off to adjust the choke, but when i turn it to adjust, nothing changes the way it's closed off. Have the throttle pulled off a bit so it's not in the way. My choke is pretty much closed, but i'm trying to make sure everything is good while I'm going through the trouble. Any reasons it's not adjusting, and any help on how to fix it (it dumbed down terms, i've no experience with carbs).

Going to set to the "default" settings on the carb, put it back on, hopefully it will start up, look for vacuum leaks, and hopefully find out what the problem is.

Looking at how my luck is, it will probably be justthe factthe carb wasn't tightened down enough when it was last put on.

Mon Nov 09, 2009 6:52 pm

I haven't had problems as major as yours, but I've chased down some carb running troubles.

learningbymistake wrote: I've taken my carb off to be able to get a good look at it. took the stationary idle pilot jet (or so I think) off to check for debris in the holes, nothing there.

At this point it's probably worth you take the carb out, apart, and cleaning it completely. Particularly make sure you take out all FOUR jets and soak them in carb cleaner, and clean out the lower body of the carb.

The four jets:
- main jet in the bottom of the float bowl
- air correction jet; you see it when you take the upper part of the carb off
- two idle jets on the right side. One looks like a brass hex bolt, the other is covered by a brass screw with a slotted head. They're just below and toward the front from the round choke element.

Quote: Any reasons it's not adjusting, and any help on how to fix it (it dumbed down terms, i've no experience with carbs).
To teach yourself, you might just pop the choke element off. Loosen all three screws all the way, and remove the bracket that holds the element in. Then take the element itself out. You can look at the way it hooks into the choke control arm.

Quote:
Going to set to the "default" settings on the carb, put it back on, hopefully it will start up, look for vacuum leaks, and hopefully find out what the problem is.
Right. Too look for vacuum leaks, you're squirting some combustible liquid directly on things that might be leaking. On the outside of the carb where the throttle shaft is. Where the carb meets the intake manifold. And particularly down where the intake manifold meets the cylinder head. Do this with the engine at idle. If the engine speeds up, that's a leak. Given your problems, you may have more than one.

Mon Nov 09, 2009 8:05 pm

Yeah... Another stupid noob question... :oops:

Vacuum port on my carb didn't have a hose on it. Just has a rubber cap? :?

Wed Nov 11, 2009 2:44 pm

Took my carb off and had drained the fuel out of it. Now, with it back on, and I pull on the throttle, theres no fuel spraying into the carb. Been pulling it a few times to try to get it primed. I can hear air like it's trying to spray in the fuel. Am I supposed to fill up the resevoir?

Wed Nov 11, 2009 5:41 pm

I had the same problem, I couldn't get it to idle right, I adjusted the jet opposite of the big and little one. If you are looking at the carb from the engine bay, the big and little jet are on the left with the throttle and the "big idle screw". It is on the other side and by itself. When it was screwed all the way in it wouldn't idle for anything, but when I backed it out just a tiny bit, my car idled fine, if that is the case, get some locktite to keep it there otherwise it gets sucked back in to fully tightened and your car will die.

So what I did was tighten the big screw down, all the way, then back it out 2.5 revolutions, and did the same for the little one next to it. The big screw on the throttle arm I have to where it touches the round part and not the steps on the carb, I then moved the jet on the other side out like 1/4 turn and started the car and it has worked fine since.

If that doesn't work have you tried just getting it to idle and spraying all the seals and seeing if the idle changes?

Wed Nov 11, 2009 5:54 pm

I set the carb to the default (2.5 out), checked the jet on the right to make sure it wasn't clogged, then put it all back together. Went to make sure I had fuel coming into the carb, pumped it a few times thinking I might have to refill the carb with fuel. Have nothing. Pulled the line off the inlet and tried, just getting air. So I'm thinking my fuel pump or my filter are jacked up. So, tomorrow, when I have some light (damn daylight savings), going to switch out my filter, and if that's not the case, probly settle for the fact my pump is bad.

After I get that taken care of, i'll look for vac leaks.

Thanks for the info on the right side jet though! Might have to loosen it a bit. Didn't put it backin super tight, but might want to put some locktite on there.

Thu Nov 12, 2009 9:59 pm

If you take off the heating element for the choke and the choke butterfly doesn't flop around, your choke butterfly shaft may be bent or something else may be binding.
If you look at the heating coil you will see a "hook" at the end of the coil. This hooks around the arm in the coil opening. That coil spring doesn't have much strength so the level must close the butterfly with very little pressure and if left alone (remove the heating coil), the butterfly should open by itself.
Take the choke assembly apart and make sure everything is straight and lightly lubed so it moves freely.

To prime my carb after thoroghly cleaning it I pour a little gas into the fuel bowl. You can either remove the top screws and removed the top of the carb; or you can carefully pour some fuel down the slanted tube that juts out into the carb throat. That's the vent tube and leads to the same fuel bowl.
You can prime the fuel pump by pouring fuel down the hose from the carb to the pump. This will wet the diaphram and get the pump to draw in fuel. Reattach the fuel hose at the carb. Make sure the brass fitting here is tightly tapped into the carb.

Once there's fuel in the carb, you should be able to pump the accelerator arm a few times and get gas to spray out of the accelerator pump nozzle. Then you can start the car and after a few seconds the fuel pump should have primed itself and it will begin filling up the fuel bowl.

If you have to do this more than twice you probably have a bad fuel pump.

Thu Nov 26, 2009 6:04 pm

Verified my fuel pump works, getting fuel to the carb, but now it's not starting. Have no idea what my problem is, and getting very frustrated. Can't even get my car to start to check the timing and see if I have the same problem with it stalling after warming up.

Always something different.

Any ideas?