Right so on my new runaround, 1991 1.6TX Jetta, I thought I'd take a look at the condition of the carb. Noticed there was loads of play and movement when touching the carb so thought I better check the condition of the flange.. Well, it turns out it was so worn down it was no longer attached! I merely pulled the carb up and slipped the flange out from underneath!! I knew I had a new spare flange in my "bag of carb bits" so thought i'd stick it on. So I took the carb off, then realised the flange is different! On the old flange, it's got a groove in where it mates with the inlet (the inlet has the groove to match obviously) but my new flange is just flat and metal! What's gone wrong here? I'm not quite sure what this flange I have is for, it may have been something to do with my first weber? I'm sure Pete or someone can share some light! EDIT: Oh, do VW sell new carb flanges? I need one that fits asap!
Looking at the pics, I don't think you've removed all of the old flange, it has split in half and the rest of it (the flat metal bit) is still bolted to your inlet manifold (four bolts like on your new flange).
Ahhh, I've removed the 4 bolts and those metal clip things.. I think what's left on the inlet manifold may be the rest of the flange stuck/melted onto the inlet! I might pop out and take a photo
Whatever floats your boat, Pete So will it just be a case of covering the inlet up so none of the crap falls down, then chiselling it off with a screwdriver/hammer? Pete: This carb actually WORKS!
Yes, it shouldn't be too strongly stuck down really. Probably just the big figure-of-eightish-shaped o-ring gumming it down.
HELP! Well I got the old flange off no problem and replaced it with the new one. It all screwed down (with those metal clip things too) no problem. I connected everything back up on the pierburg that I'd taken off to get at it.. Then bolted the carb onto the flange correctly. Double checked the connections off a list I made of what I'd unplugged, etc. so I didn't miss anything. Now the car won't work!! If I turn the key, the engine will rev up once to about 3k, then drop down and die. You can keep the engine going by holding the throttle but unless you keep the revs really high, it'll cut out! Pretty much have to keep the revs constantly over 3k or it'll just die out. Checked the autochoke and everything seems to be fine. I just can't see what's different since all I've done is changed the rubber flange! Any ideas? Desperately need to get it sorted so I can get her MOT'd!
Have you definitely reconnected the Idling/Overrun Control Valve (two pin electrical connector) shown near the top left in this pic, but right at the back of the actual carb?
Is the connector that plugs into it a wide(ish) black rubber one? If so, I checked it and pushed it in but I can double check this in the morning. If this is plugged in properly and it's still not working, what would you recommend?
Did you take the carb right off, including disconnecting the accelerator cable? Just wondering if you've done that, and then reconnected it with insufficient slack in the inner cable? Easily done . Easy to check though; with everything swiched off, try lifting the accelerator pedal with your finger. It should move freely upward about 1.5-2cm at the very tip of the pedal. Other than that, I can only imagine you've dislodged, or cracked an old vacuum hose. Try to get a few pics of the carb from various angles, might help us spot something. Best of luck.
I didn't disconnect it, but it got bashed about (along with other bits) while i was holding it out of the way while I got in at the flange. I'll check it over tomorrow then Things I removed to get in at the flange: Short coolant pipe that goes into the auto choke (the one closest to the windscreen) a coolant pipe that connects into the expansion element I think. It's got a long horizontal piece with a right angle where it goes into the carb? Auto choke plug from (black cable with red end) Black vac pipe that goes from back of carb to airbox Brake servo vac pipe that connects to the 3 way things that's linked with the.. waxstat? (green ball?) I held the carb to the left hand side and had it tipped on it's side to get in at the flange. Didn't remove the screws holding the two halves together, just the three long ones. I'll get some pics too. I've got the whole day to fiddle with it tomorrow once I've sorted my ARB bushes! Struggling to get the new bushes back on! I think I may just take it off like I did, check everything and put it back on again. Hoping I've just knocked something when I've been fiddling. I've got 2 spare carbs to steal bits from if need be!
my thoughts are its had the mixture adjusted for the MASSIVE air leak you would have got thru that busted flange, now its running far too rich.
Well I found a very split vac pipe on the back today. It connects from a bit with a light blue ring on it.. and connects to a 3 way adaptor. Not sure what it is, but I replaced it! My Dad decided the cam belt was too slack so tightened it up - in the process, knocked the Timing out so it doesn't run! Just backfires [] So we'll get it timed and see how it runs. Any tips on re-setting the CO adjustment screw? What's an average "working" level I can start with?
well get the timing sorted first, then see if it will run. dont forget to check the rotor arm position as this can move when the belt is played with if it runs ok then id be tempted to leave the CO alone, othewise yoiu'll need a CO meter or ask a friendly garage type person to tweak it for you. Before you pay for it to be done though make 100% sure everything else on de carb is hunky ory, and the ign timin is spot on
If it was the blue hose in this pic I can't see that being the problem, I'm afraid, stuff up there is all at very close to atmospheric pressure so leaks there don't matter a lot. For the CO screw, if you look at the picture of the exploded view I posted, it's right at the top, inside that little turret/tube. Down at the bottom of the tube there's a little vertical slot which lets the air in. If you adjust the screw so that half of the slot is covered you won't be a million miles out. Trouble is, you can't see the slot without removing the whole turret/tube IIRC, and there's a little o-ring at its base that's probably ready to turn to dust at any disturbance.
It was the red tube on the pic that I swapped Righteo, I'll get it timed and go from there then. I think I'm best off leaving the CO mix for now then.. My Dad is complaining it's my fault the car no longer runs.. "If it ain't broke, don't fix it! So why did you fiddle with the carb?" "Did you see the condition of the rubber?!" Rear brake pipes to do tomorrow.. As well as un-seizing the brake compensator valve mech.. Whatever that is!
Well, it's now Timed and still nothing! I've been told to remove the carb and flange and start again, but put some vaseline in between each layer to make sure there's no air leak. Any other ideas of things to try? I'm getting frustrated!
Well, it now runs better now that it's timed, etc. and when running the engine it sounds healthy. I can now hold the idle at around 1k with my foot, but if I let my foot off it'll drop down and cut out. So it must be the autochoke! ..But what part of the autochoke is stopping it from working..?
Well, I'd start by looking at this bit, the 3/4 point unit: The plunger bit to the left of the yellow arrow moves in and out as the manifold vacuum levels change, in order to move that screw to the right of the arrow which directly opens and closes the primary throttle. If all is well, this holds the idle speed at a steady level. It could be that this stuff got adjusted to compensate for the leaky flange, and now that plunger isn't coming out far enough to let enough air through the carb. Get someone else to sit in the drivers seat and hold the revs at exactly 1000 while you look at this stuff under the bonnet. When the engine is at full temperature the plunger/pushrod should be sticking out about 8-9mm, and there should be contact with the screw where the arrow is. I suspect your pushrod has been adjusted so that it doesn't come out this far, or the screw it pushes on has been moved. You should probably expect a very small gap there, 'cos in this test, the throttle is being held open by your father/brother/mate/girlfriend via acc. pedal and throttle cable, but with a normal idle speed of, say, 950rpm (dunno exactly what it should be for that car) it shouldn't be more than a smidge away. The adjustment, if needed, is right at the back of the 3/4 PU, a 13mm 'nut' labelled '13' in the picture in post #15.
