Club 80-90 Forums

Probably no need to play with the timing, sounds like you have the "Pierberg cough".
This is usually caused by the accelerator pump over/under delivering and/or dribbling rather than spraying, as suggested by our friendly VW trained fellow, Martin.
Another common one is choke pull-down diaphragm leaking, makes it lean at low revs which folk then compensate for at idle with the mixture screw. Makes it tickover fine but just above (ie as you first press the throttle) it goes lean for a moment and coughs, then fine above that as small air leak makes little difference at increased revs.
If you want to fit the carb rebuild kit, adjust the mixture by leaning off (screw in) 'til tickover just starts to drop, then open screw up by a quarter turn, then come over for mixture and timing check/adjust I can sort that for you with pleasure.

That sounds like a good plan! There's a pull-down diaphragm in the rebuild kit, so as long as I can make it run (and that doesn't sound too difficult - famous last words) I'll bring it over to you, thank you. We can look into the specifics of the leisure gas installation too.

I don't think you can service the choke pull down
The rebuild kit I got had membranes for accelerator pump and part load enrichment valve

If you haven't done it already then some rebuild porn here
http://s1145.photobucket.com/user/paul_ ... ierburg2E3" onclick="window.open(this.href);return false;

If its an early carb with code 025 129 015 A then it possibly has a different float valve from the later kits generaly available

Ah, you're right. Earlier I Googled to see what the choke pull-down diaphragm looks like and found this, which I recognised from my rebuild kit. But I think Google found that just because it was a diaphragm from a Pierburg carb.



So if I have got a leaky pull-down unit diaphragm then I guess I have to wait till Brickwerks get replacement units back in stock?

Mine is an 025 129 015 H carb, and the rebuild kit I've got is for the 19mm push rod (I checked before I bought the kit).

Yes thats the accelerator pump
Easy to check choke pull down vw heritage sell them if its faulty
http://m.vwheritage.com/productDetails. ... mID=169562" onclick="window.open(this.href);return false;

Andrew at Campershack is your man.......he has both the time and knowledge to sort this one out for you..well worth the short trip over. Lovely straight up kind of fella.
Don't forget the distributor vacuum advance.....just a quick suck on the pipe then move on if it holds vacuum.

Martin

I stripped my carb down today, cleaned all the parts in paraffin, and reassembled it with the rebuild kit. I found a bent fast idle cocking mechanism, just like 1_eyed_jim's (his photo)



I straightened it up, and fitted the carb back in the van, and to my great relief the van started up from cold, and even better, the choke fast idle now seems to work - first time since I've had the van . In fact, the fast idle feels a bit too fast, but that's maybe just because it's previously been adjusted up to try and compensate for that bent mechanism.

I took the van for a run round the block, and as it warmed up it began to run very lumpy - wouldn't idle, low on power, felt like it was 'missing' under throttle - symptoms which seem to suggest the choke isn't disengaging perhaps? It was too dark to try and diagnose the problem this evening, and I'll whip it off for a better look tomorrow, but can anyone think of anything obvious I may have forgotten or reassembled wrongly to cause this? To the best of my knowledge I didn't change any of the adjustment screws, so it's most likely a mistake with the reassembly.

All fixed - I took the choke mechanism apart, checked it, greased it and reassembled it. Not sure what the problem was - maybe all my paraffin cleaning had made the mechanism too dry and it was binding - but now it's running quite well. Starts ok from cold and runs ok when warm. The very fast idle on cold start seems to have gone too though - not sure if that's fixed or broken now!

Time to see when Simon's got a spare appointment I think.

E D I T: Did I say Simon? I meant Andrew.

I took my van to Campershack yesterday, and Andrew worked his magic. He discovered that the engine was running lean, especially at higher revs, so through a combination of adjustment and blasting all the jets and fuel ways with cleaner and a compressor he soon had everything running sweetly. He also adjusted the timing and checked the valve adjustment. All in all it was exactly what I'd hoped for.

Obviously it wasn't possible to check cold starting once the engine was up to temperature, and this morning I found that it starts well from cold, and will run without the gas pedal after 10-15 seconds - that's a huge improvement on the several minutes that it used to take. I'm pretty sure the fast idle isn't engaging from the gas pedal though, even though the mechanism looks ok. I suspect this may be due to excessive slack in the throttle cable (which Andrew pointed out yesterday) - maybe I can't quite depress the throttle enough to engage the fast idle properly. Should be easy enough to check.