Jetta 1.5 GL - starts but won't idle, carb/choke issue

Hi all,

Yes it's another problem with a Pierburg carb - i've got a 1B on my '82 Jetta GL.

Have replaced all the fuel hoses, fuel pump, swirl pot, plug leads, dizzy cap, air box and various other bits after a small engine bay fire.  On getting everything built up and making sure there was a spark, managed to get the car started and it runs ok on all four cylinders, only problem is that it won't idle without revs and when it's warm it cuts instantly when you take your foot off the gas.

Haven't touched any of the settings on it since before the fire and it ran fine then so it shouldn't really be the idle settings or anything like that.

Have tried stripping and cleaning the carb, replaced the gasket, and blew compressed air through all the jets to try to clear any blockages but to no avail.

Only thing that isn't totally pukka is that the vacuum advance on the dizzy isn't functional (diaphragm melted) and I haven't managed to get another one yet so this vac hose is blocked off at the carb

Thought it worth putting it up here to see if anyone has had similar problems?  Any idea which is the idle jet in this carb?  

I'm aware that the weber 36TLP is much more highly regarded but they're not cheap or easy to come by so would really like to try everything on the pierburg first- it was surprisingly reliable for the 29 years it's been going!

Thanks in advance,

Greg

If it runs buit dies as soon as you touch the gas, to me that points to it being too lean - richen her up a touch and see how it goes..

 you can buy replacement vac advance capsules without having to repllace the whole dizzy but trry the mixture first..

Thanks Nick - it's actually the opposite in that it runs fine with revs, and pulls ok when i've taken it out for a spin round the block (despite there being no vac advance).

However when you take your foot off the gas to stop (e.g. at a junction) it won't idle, it cuts out almost immediately. It also does the same when trying to get it to idle when warm when it's stationary, even if you back the revs off very gently.

Very frustrating after a lot of work to recover it from the fire!

I think the engine bay fire may be your answer here…
Have you checked for air leaks? Try spraying easy start around the carb mount and see if the revs climb.
The carb sits above the exhaust manifold right? So if your carb is leaking… onto hot exhaust - it's BBQ time.

From tinkering with my pierburg 1b carb… I never found an idle adjust screw. Just what was labelled on the diagrams as a 'c02' screw. I never could set it up. But I CAN tune and balance twin webers / dellortos. So yeah… they're rubbish. I don't even think there's an idle adjust screw?!

I had a naughty pierburg 1b carb my 1.5 gl golf set up and it was total pants.
They are black magic, the auto choke had it's own feelings about what it should be doing (no wax stat either). Not to mention the maze of vacuum takeoffs, resevoirs and such (mystery green egg of pain).

You know what I'm going to say now…..
Get a weber 36 tlp.
I sold mine a few years back for £60 - bargain if it makes the car run - which it should. I just had to rig up the 'go cable' with a spring for it to work and I never looked back.

But you're right, they are rare. You could go for a bigger boys carb and a shiny new manifold?

Thanks Mogs.  

I've checked for air leaks - and there's no increase in revs when spraying quick start around the seals so that's not what's stopping it idling.  Could still have been a carb leak originally though, as i've replaced the gasket since the fire.  I got a second pierburg 1B for a tenner (in the absence of any Webers anywhere) and have tried various combinations of the parts of the two carbs with the same problem every time.

Am going to look around for a weber but i'll let you know if i find any rocking horse s*** while i'm at it…

There is an idle adjust screw - it's on the left lower side of the front facing side of the carb. Didn't help when I upped it a bit!

Greg

Are you missing any vacum pipes / takeoffs, maybe you forgot to hook them up after the fire or they got melty and need replacing.
I think I can remember pulling a vacuum hose off and the idle went to poo.

I'm not really sure on how all the vacum crap works, but there's one on the airbox which is useless, another one from the carb to the mysterious green egg of pain, one to the brake servo and another to the distributor if it's got the vac advance. Goodluck.

There's some nice piccies of a pierburg for weber tlp swap thread here. http://www.vwgolfmk1.org.uk/modules.php?name=Forums&file=viewtopic&p=153687

Hi - thanks again Mogs!

Will double check the Vac pipes as well, but i'm pretty sure they're all generating and holding vacuum and have tried all the possible configurations.  The vac advance shouldn't be doing much if anything at idle so it shouldn't be that plus I've tried playing with the timing to see if that sorted it and it didn't so that should rule that out.

Likelihood of getting a 36TLP is roughly nil so I think i'm going to chance a 34ICH - its the one for the earlier 1.5's, uses the same mountings and is available for the same engine size.  Hence i presume it should be jetted ok etc and should work; i've spoken to a coupld of carb specialists who have been broadly positive on this.

Would welcome any thoughts from anyone on the forum though especially if anyone's tried it!

Greg