engine stalls when braking

[tmckinn]

My 30 Pict-3 carb is driving me nuts. I recently rebuilt the carb (Ghia w/1600 sp and dual vacuum advance distributor). Now, after "fixing" the carb by rebuilding it - I can't get it back to the way it was before I "fixed" it. The car often dies when I'm braking to a stop.

When the choke is on, no problem. Also, it seems when the engine is hot it's okay - not great. It sometimes acts like it's going to die by lighting up the gen and oil lights when I brake. The in-between stage, after the choke turns off and before it gets real hot, that it is the most prone to dying.

I've read about 13 different manuals/articles/posts, etc. on the proper way to adjust the carb.
- valves and timing are fine
- the choke works
- it idles just fine at 800-900
- checked for leaks by spraying wd40
- during rebuild, changed the emulsion tube (the old and new emulsion tube were both marked with 125z, but the new one had fewer holes)


Does the emulsion tube factor in to this problem? Could it be running too rich? If so, how does it run to rich if the carb is adjusted according the manual and idle speed is correct? How do you get it more lean?

Any ideas are appreciated (up to and including a shop recommendation)!

I live in the Seattle area (Eastside). I'd hate to take it to Buttera Motors because the old timer there told me not to rebuild the carb, that I'd never be able to clean it and to just by a new Brazlian one instead. So you can understand my reluctance to go back.

Thanks for your help.

[oxygen]

my bus dies often when i brake to a stop. I have adjusted the idle and the valves. I am going to check the timing this weekend (it backfires every now and then when i brake). But do i need a new carb? or to rebuild it?

[tmckinn]

Oxygen - This might be a case of the blind leading the blind. I'm not very experienced with carbs, but I can read a manual just like the rest of them.

Everything I've read has said you need to adjust valves, points, timing, and carb - in that order only. If you adjust the carb before the timing, you're just treating a sympton not the problem. Also, from what I've read, carbs are really pretty timeless and don't wear out (except for the throttle plate bushings). The jets may erode, but I understand that is pretty rare.

After my experience, I'd hold off rebuilding the carb just yet. The idiot guide advises against it and has some tips on cleaning it from the inside. If you decide to rebuild, read up on what jet sizes and emulsion tube, etc. your particular carb should have (and locate a parts source before you start, just in case you need something). Also, verify your distributor and carb are supposed to go together. Since my car is 34 years old, I don't know how many people have fiddled with it and I don't assume anything is exactly the way it supposed to be until I verify it myself. Also, I assume that anything that is preset at the factory (volume control screw) has long since been messed with.

Check this stuff out http://www.type2.com/library/exhaust/backfire.htm
http://www.type2.com/library/fuel/cutting.htm
http://www.type2.com/library/fuel/kuhn1.htm
http://www.type2.com/library/

[H!]

Hullo!

if you are finding that your bug cuts out when you brake I am asuming that you can keep it running if you blip the throttle??

If you can there is a "swan neck" in the carb. This is a brass curved piece if tube ( v small ) that has a ball bearing or similar inside it. if this isnt spot on you will find it keeps stopping the fuel getting in. I have rebuilt a carb then had the same issue as you. Howeveer there is so much oppurtunity for something else to be wrong. ie leaks, etc etc. Might be worth trying the swan neck however in reality if possible a new carb given that it is a stocker carbv and lower down the price range would be easier.- but hey wheres the satisfaction in that!!

[Adventurewagen]

I believe that there is a different problem going on altogether. I have had this problem and no matter how much you tune the carb it is not going to solve it, especially for Oxygen who wrote:

[70 140]

Adventurewagen. Only the busses had those vaccum assited brakes, but good description.

[Adventurewagen]

I should have been more clear that I was directing my post toward "Oxygen" since he has the same problem with a bus. I did mention that the vacuum line was only in the buses and that I wasn't sure about bugs.

[70 140]

Adventurewagen,
I wasn't meaning to offend you. I was confirming your statement that ghias had no vacuum assited brakes. "In 1971 VW put a brake booster in buses, I am not sure about bugs though." I was simply confirming this for other readers.

[slammed73SB]

i had the same problem a couple of weeks ago. after some extensive searching i found that my choke wire had come loose and was hanging close to the engine tin, everytime it hit the brakes it would touch the tin and ground out thus shutting off the engine, replaced the connector and presto, no more dying

[-Rusted_Radio-]

Dies right when you hit the break or when you sit for say 3 seconds? My spark plugs needed to be gapped and cleaned, and now it never dies. -wEs-

[dubman67]

Your idle mixture might be too rich, I've had that problem before myself.
_________________
67 Bug
62 Double Cab
[url=https://www.vw-mplate.com/mplate2-54829.png]Click to view image[/URL]
"At 17 got my first Volkswagen...and mastered the life long art of dragin...." Ice Cube

[tmckinn]

Case solved. My idle mixture was too lean, much too lean.

A racing shop suggested the following test.
- remove air cleaner
- while idling, slowly put hand over on top of carb (to restrict the air)
- if idle speeds up while restricting air, the mixture is too lean

I ended up unscrewing the volume control screw on the 30Pict a good 6 or 7 times as a starting point.

All of the manuals (Bentley, Idiot's Guide, Chilton, etc.) say the 30 Pict mixture is set at the factory and not to touch it. This is advice is not very helpful considering the carb is 34 years old and has been visited by numerous mechanics and previous owners.

There are a number of good articles (search in Samba as well as Google)describing how to adjust the 34-Pict carb. I followed this advice to a "T". Screw the volume screw in all the way (don't force it), then back it out 2 or 3 times for the starting place. This didn't work for my 30Pict with stock jets (112 main, 65 pilot, 125z air correction).

Thanks to everyone for their suggestions.