Hi, I have a J reg mk2 golf ryder that has devolped a problem when starting from cold. It has the dreaded Peirburg 2e2 carb with autochoke. When started from cold it won't idle and needs a little bit of throttle to get it to tick over and to stop it stalling. Once the engine is up to temp it idles fine. Been looking into it and it seems that the 3/4 point unit pushrod is in the extended positon when the engine is off. As soon as the engine is started it fully retracts. Should this rod stay extended until the engine is warmed up ? ( Seems like it should as it increases the revs by pushing foward the lever ). What actually makes the pushrod extend and retract ? All thoughts and suggestions greatly received.
been investigating abit more. Checked out the autochoke unit. There was no 12v ign feed. Found out the thermo switch at the front of the engine is faulty, it should pass current when cold, it was open circuit. So bridged that out with some wire and then got 12v at the autochoke. Still no change. Now thinking there is something wrong with the autochoke. Any ideas ???
Your 3/4 point unit sounds OK to me. It should be fully extended with engine off; then if the weather is pretty cold (winter only really) it should stay fully extended for a few seconds under the control of the thermo-time valve (TTV). At this time of year I would expect it to retract immediately, to an intermediate position (about 8-9mm extension) as soon as the engine starts. A strong spring inside the 3/4 PU makes the pushrod extend; and manifold vacuum acting on a big diaphragm makes it retract. The intermediate position is held if the second vacuum connection is opened by a solenoid valve on the back of the carb. The idle speed during the first 4 or 5 minutes of running from cold is actually governed by the waxstat, via a mechanism on the other side of the carb. This creates a wider minimum throttle angle which gradually reduces as the coolant warms the waxstat. Only when the waxstat is fully extended does the warm-up cam disengage from the primary throttle mechanism and let the 3/4 PU take over control. Have a look at this diagram, the waxstat is the bit on the left with the orange-coloured coolant going through it: I'm not sure that your waxstat is working properly, but TBH the usual early symptom of failure is high idle speed that takes ages to reduce after a cold start. Did you have this symptom before now? I'm not sure if a totally fecked waxstat could produce your current symptoms by allowing the cam on the warm-up lever to sit so far round anticlockwise that it doesn't ever touch the 'stop' on the primary throttle mechanism? You may be able to see if this is the case if you start it from cold, and keep the engine running just long enough that it will keep going without your foot on the pedal, then nip round and have a look to see if you can see the 'stop' and where the cam is relative to it. When the engine's off that stop will be miles away, as the 3/4 point unit, at full extension, will be keeping the throttle even wider open; so you can't check it then. Have a browse around this thread if you haven't already. IMHO good things to check out would be the waxstat, and pulldown unit (and vac hoses going to it). These would be the two most common failures I think. Could be a few other things though! Take some photos of the carb in various states of running/non-running; fully warmed up etc, if poss.
I'm gonna call 'BS' on myself there, Just had a look at a spare carb with no waxstat at all on it, and it's impossible for that mechanism to be far enough round anticlockwise to do this... I suspect your problem must be related to the choke flap not doing what it should be doing. Or a completely unrelated problem like an ignition fault causing the engine to struggle when cold. Edit: just seen your second post. Good detective work on the autochoke electrical heater, looks like the thermoswitch died*. You should also check that the autochoke water housing is electrically connected to battery negative. Ideally put a current meter in series with the feed to the heater and confirm that it takes about 1 Amp. Check out the pulldown unit next, and do check the vac hose that feeds it from low down on the front of the carb, mine was leaking just where it comes off the carb. * But check this again in the morning if you can. It switches from on to off at a pretty low 35C IIRC, so if there was any warmth in the coolant at all it should have been off.
Hi , thanks for the reply. I have been investigating a bit more and have checked out the autochoke unit. It wasn't getting a 12v ign feed from the thermo switch (which is faulty), so i put a piece of wire across the 2 terminals and got 12v at the red autochoke connector, still no joy. Now thinking a fault lies in the autochoke or pull down unit. As for the waxstat, I have yet to check it, but I have never had it idling too high before, which seems to be the common fault with faulty waxstats. So what controls the idle from cold ? The autochoke ?, 3/4 point unit? or the pull down unit.? I'm confused.
ok, thanks for the advice.Will try and check tomorrow. There seems to be a delay in posting and it appearing in the thread. is this normal ?
Doesn't look like there's a delay anymore, strange. What actually moves the choke flap ? the pull down unit, the autochoke ? Bit confusing
New users sometimes do experience delays. I must admit, your second post seemed to appear after my first answer, though the times suggest otherwise . I think it's a spam-prevention thing. There's a bimetallic coil inside the choke housing that gets heated by the electrical heater, and by the coolant circulating in the outer housing. This causes it to unwind, and move a linkage which pulls the flap open. The pulldown unit also opens it, over-riding this bimetallic thing to give a fast opening, in two stages, of the first few millimeters. There's even a third mechanism, called "wide open kick" which forces the choke flap open if you go full-throttle during warm up. Simple, eh?
what's wrong with a simple choke cable I check the autochoke and pull down unit and see what i get. Looks like i need to get a new thermo switch. The other thermo switch for the pre heater went years ago, never bothered replacing it.
Just got back from driving the car and checked the autochoke unit, it was very hot and so were both the pipes coming from it. Also had a look at the pull down unit , theres a cable that goes up and inside it( accelarator cable ?).I moved the cable upwards and the revs increased. Is this normal ?
Pulldown unit is number 3 in this pic: Two vac hoses go to it, no cables. Dunno why that last pic link died, try number 18 in this one:
Must of got my wires crossed , probably looking at something else at the rear of the carb. I put an multimeter in series with the autochoke supply and there was no current drawn. Also checked that the autochoke case was grounded , which it wasn't. Looks like there's a fault inside the autochoke. Didn't have time to take it off and have a look.
There might be mate, but I'd say your lack of earth connection is being caused by a broken earthing ring which you won't see unless you remove the metal autochoke parts from the plastic fitting that connects it all to the main carb body. (No need to do that though) If you look at this picture: The pink arrow is pointing at a plastic part that insulates the autochoke housing from the main body of the carb, thermally (desirable) and electrically (inconvenient). There's meant to be an alloy 'ring' that goes between the autochoke's metal parts and the plastic fitting,with a tag that goes under one of the screwheads that mount the plastic bit to the main carb body. These are very fragile though, and I've not seen an intact one on any carb I've looked at. So the yellow arrow points to my solution, a separate earth wire connecting the metal housing to another definite ground point (rocker cover earth connection in my case). You just need to clean up the areas on (both sides of) the metal parts where that earth crimp is going, to ensure a good ground. Whilst you're at it, check that the grooves/lines are correctly aligned where the blue arrow is pointing. If not, loosen all three screws that hold the metal lockring down, and rotate the choke housing until they do align.
Update; The autochoke case isn't grounded, so I grounded it using a multimeter to check the current draw. I took 1.2A , but made no change to the idling. Should there be anything that moves or makes a noise when the autochoke is working ?
Err, yes, the choke flap should move from closed to open. (Over a few minutes). The first 5mm or so of opening should happen pretty quickly, as mentioned above I think, due to the action of the pulldown unit. If this has failed it will cause the engine to struggle for air (and overfuel badly) during the first minute or so of running from cold. Get someone else to start the car and give it just enough go-pedal to keep it running while you watch what the choke flap does over the first 3 or 4 minutes from cold (airbox off but with vac hoses still connected). Make some notes about what it does and post your results on here. Engine's got to be cold to see this stuff working; if there's any heat in the coolant, the choke flap won't start off fully closed.
Thanks for the info. Will have a look at the end of the week, don't have time to look at it before work, when it's cold. Looks like my problem could be a combination of things ; the thermo switch faulty, autochoke ground missing and from your description above , sounds like the pull down unit could be suspect. Been trying to track down the thermo swich, gsf don't sell them. According to ETKA the autochoke one is red and the preheater is grey, which is wrong, isn't it ? Looks like vw maindealer for those ?
I think the part number you need will be 191919369B, which is described on vagcat.com as "thermal switch / for automatic chock 30/40C 20MM 2 pin grey / carburetor engine ". Not too sure what an automatic chock is, mind. Further up the listings there's a screw-in version with an M10 thread that's described as being red; possibly the one you were looking at? Plenty of room for confusion... I doubt you'll find it except at VW. Do bear in mind though that this will certainly not be the main cause of your trouble. Maybe try to get to the root of the trouble before spending anything significant? As for the pulldown unit, Drew21 gives a good description of the best test procedure in Post #2 of the FAQ. Can be done in about 30 seconds, especially if you have a spare length of vac hose knocking about. If your pulldown passes this test, and you've checked the vac-feed pipe to it from low down at the front of the carb (and all the others associated with it), then I'm running out of ideas. Except to re-iterate that the behaviour may be completely unrelated to the carb; always try to rule out ignition and mechanical faults first.
Managed to have a look at the carb today. I took of the air cleaner so i could see the choke flap. It was at an 45 degree angle when i started the car, is this normal ? Started the engine a gave it enough throttle to keep it going, was a bit lumpy. I got a stick and tryed to close the flap and got it to stall, which i guess is right as it would be starved of air ? Checked the ignition components and found the rotor arm had corrosion and the centre has started to disintegrate. The leads were ok The dissy cap also had corrison and signs of deteriation. Drove to GSF, got a new cap and arm, fitted them. I checked the choke flap now the car was warm and it was in the fully open position and there was resistance to pushing it closed, is this normal. I also disconected the vac pipe going to the green vac resourvoir ball and nothing happened, is this correct or should it of have an effect eg, uneven idle or stalling ? Then put the pipe back. Checked all the vac pipes for spilts.While i could not find any some of the outer woven material had rubbed through to the rubber pipe . The car seems to run a little better now, but will have to wait till it is cold again to see how it starts. Any ideas ?
Hi, been a while since i last posted about this problem. Been looking into this problem recently as wanna get it sorted before the cold weather, which is nearly here. looks like the 3 point unit push rod is fully retracting as soon as the car is startred from cold and it needs to stay out for about 5 mins to keep the revs up , while the car warms up. What would cause this to happen ?
As I tried to describe in post #3, apart from the first few seconds from cold, it's the waxstat and associated mechanism that keeps the revs up during warm-up, not the 3-point unit. Quite what's wrong with that system on yours I don't know though .
