34 PICT 3 Accelerator pump

[Who.Me?]

Posting this here, because I couldn't find a thread to append it to. Hopefully it helps someone in future...

I bought the Haynes Bay bus manual a while back and reading through the bit about rebuilding the 34 PICT 3 carburetor, I noticed something that the instructions which come with the rebuild kits don't tell you, and none of the 'how to' guides here or on YouTube etc. mention - the accelerator pump diaphragm needs preloading.

To preload it - attach the pump cover but don't tighten the screws. Pull the throttle lever down fully and hold it down while tightening the pump cover screws.

I've rebuilt my carb a few ties but haven't been able to get anywhere near close to the accelerator pump volume specified in the manuals. This time I used the Haynes procedure for preloading the pump and it finally gives the correct volume. The pump adjusting cam also has more effect now.

Also; about measuring the output - VW recommend using their tool 119 to collect the fuel from the pump squirter to measure it.

It's basically an S-shaped tube that you thread down through the top of the cab and hook up to the squirter. It's supposed to collect all the fuel (no splashing) and because it exits through the top of the carb, it still allows the throttle plate to open and close fully, so you get full squirts from the pump.

I made my own with some copper tubing, but it's a bit crap (my version and the concept in general).

I realised when I had the carb apart on the bench this afternoon that it's much easier to take the top off the carb, pull the squirter out, turn it through 180 degrees, and stick it back so it squirts over the side of the carb. The fuel squirts cleanly in to the collecting jar and it's a lot easier easier to keep the fuel bowl topped up as you go.

Hopefully this'll be useful info to someone.
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Andy


Looking for info on my truck's history. Are you from Campbell California or nearby. Do you recognise it? ... http://www.thesamba.com/vw/forum/viewtopic.php?t=636786

[DesertSasquatchXploration]

Yes nice post

The replacement diaphragms do not fill enough to allow full squirt adjustment. You will have a gap between the arm and diaphragm and of course creating a flat spot under acceleration. Need to be bench set so you know the max adjustment. I bought a red alcohol rated diaphragm it was a joke not even half the capacity.

Any case you must of got a good Diaphragm and the correct setup procedure helps a lot that's all we can do you get what you get.

[NachoCar]

see any issue with loosening pump cover and pre-loading with carb installed?

Don't think I ever read anything about this before.

Thanks!!

[bsairhead]

Why would a couple of pumps not do the same thing?