1.6/1.8 Pierburg 2e2 carb FAQ

[rubjonny]

Here is a list of Pierburg components and troubleshooting tips:

TTV & idle over run valve:
These should both get 12v when the ignition is on, and there should be an audiable 'click' from the engine bay when the key is turned.

3/4 Point Unit:
When engine is off, should be extended to 14.5mm. When engine is started should retract to about 8.5mm after a varying delay, depending on temperature.

Pull Down Unit:
When engine is running, you should be able to close the choke flab by hand easily until the last 5mm or travel, then resistance should be felt. If not the pulldown unit is defective or incorrectly adjusted (it has a small screw on the end of the plastic lever, but this should not need to be adjusted)

Inlet manifold preheater:
Located at the bottom of the inlet manifold, looks like a hedgehog. The electrical connection is at the back of the engine bay behind the carb, should get 12v when engine is cold, should switch off when engine has warmed up. (controlled by red temperature sender, see below)

Vacumm Unit Stage 2:
This opens the second throttle butterfly when you have your foot down, not had a problem with this myself but I imagine sympoms for a failed unit would be no power under full throttle.

Waxstat, also known as 'Expansion Element':
Helps control the idle untill the autochoke switches off completely. Is full of wax which is heated by coolant. As the wax expands a pin exends from the unit pressing a lever which brings the idle down. Check by throwing into a bowl of hot water, the pin should extend. This has been known to fix dodgy units as it 'resets' the wax apparently!

Autochoke:
Should get 12v with the ignition on & engine is cold, should switch off when the engine is up to temp. (controlled by the grey sender, see below)
The autochoke should pass current, test by placing one prong of a multimeter on the plug, and the other on the autochoke housing.
You can check the autochoke heater visually by removing it and checking the heater spring around the outside of the unit, looks like the kind of spring you find in a ball point pen. When refitting, align the mark on the housing with the notch on the choke.

Temperature Senders:
At the front of the engine block there are 2 temperature senders, red & grey. The grey sender controlls the autochoke, the red controls the inlet manifold preheater. When the engine is cold these should pass current, when the engine has warmed up they should stop passing current. You can test units from the scrap yard by putting them in a tray filled with boiling water (just immerse the metal bit at the bottom!) to make sure they switch off correctly.



Last but by no means least, the inlet manifold coolant channel o'ring, the o'ring degrades over time eventually blocking the coolant channel completely. Often overlooked this is key to having a 2e2 carb that actually works! If this coolant channel is blocked expect poor running when cold, smoking, petrol smells, engine overruns and having the engine rev up to 1.5k+ at random until the engine is VERY hot.
Start the engine from cold and feel the autochoke unit, it should get hot quickly. This is becasue it needs a good flow of coolant from the back of the head to work properly, when the car has been running for a few minutes it should be boiling hot to the touch.

Before you start, MAKE SURE you can reach ALL 6 bolts on the inlet, the third one from the right is wedged between the inlet and exhaust manifolds and is tricky to get to. You'll need a new gasket and the o'ring, part 32 in the diagram below.

First take the carb off:
Remove the airbox
Remove the fuel line from the carb
unplug the 2 electrical bits on the left side at the back
remove the earth connection from the front
Unplug the vacuum connection to the green reservoir
Remove the coolant connection to the inlet manifold
Remove 3 securing bolts
Check the condition of all the vacuum pipes, do one at a time its a bit complex back there

That should give you enough slack to move the carb over to the right out the way, next get the manifold off:
Undo all 6 bolts, remove manifold.

Then lever out the knackered old oring and clean up the hole it came out of. While you're here check the inlet manifold preheater. Then fit the new gasket & oring, refitting is the reverse of removal

Edit: Whilst you're there you might want to replace the core plugs that are only accessible when manifold is off. (thanks for the tip pmhpmh!)
Edit2: While the manifold is off check for free coolant flow, bits of o'ring or other garbage might have dislodged and ended up stuck in the inlet as what happened to Spanish Mike, see page 4

[rubjonny]

Originally Posted by drew21

the channel heater unit should get a permanent 12v and is earthed through the carb, if not working check the volts at the connector and check the carb earth strap

3/4 point unit, when you turn the engine off the piston should fully withdraw and the extend to its starting position. Failiure to do this indiates a fault with the overrun solenoid.

pull down unit
to check for vac leaks in this unit attach a pipe to the lower port and unplug the upper port. Suck on the pipe. The arm should move a small amount and then stop when the vac collapes. Then if you put your finger over the upper port ad keep sucking the arm should withdraw a bit more and hold vacuum. If it fails to hold vac then replace.

hot air flap, this can seize during the summer as it doesn't get much use. So as the weather gets colder its worth spraying ome WD40 on this and making sure it moves

poor running can be caused by air leaks around the base flange, can be a cheap fix if you're having problems with missing at idle. To locate vac leaks try spraying gamping gaz (carefully) around the vac pipes and the base of the carb. Changes in idling should be heard when you find the leak!!

Originally Posted by mark25

some stuff about the part throttle channel heater:

With the ignition off and the heater supply wire dissconnected, the resistance of the heater is about 3.8 ohms measured back to the negative of the battery. So this value includes all the wiring and earth straps back through the carb and engine.

With the ignition on and the heater supply wire connected, I have 11.3 at the heater supply wire. Therefore I am loosing about 0.5v across the switch or relay that controls the heater.

I think the symptoms if it’s not working are; the car runs rough until the engine is totally warm. You can get round this with a manual choke by just leaving it out longer. With mine I can put the choke in as soon as I’m out the drive way, in all but the coldest, ie –5oC, weather.

Mark

EDIT: the above tests were done on a unit that had been transfered to a weber.

[rubjonny]

Originally Posted by EZ_Pete

I shall abbreviate pulldown unit to PDU for convenience .

I'm going to assume that you have tested the old unit in accordance with Drew21's method detailed above, and it has failed. You should also check carefully all the vac hoses going to the PDU and replace if they look anything but recent. The one that goes down to the bottom of the carb from the "A" port on the PDU may degrade/perish due to proximity to manifold warmth.

Tools required:

In order to show the process clearly, I've photographed a stripped-down carb, and you'll notice that the PDU is incomplete too...but not in any relevant sense.
I managed to change one of these without stripping any parts from the carb, but it is a bit tricky, as the autochoke assy is rather in the way.

Judicious juggling and bending can remove the old (easy 'cos it doesn't matter if it breaks) and insert the new; you run the risk of snapping plastic parts, however. You may prefer to make a note of approx. how far the adjustment screw protrudes into the 'slot' and then remove it to make insertion easier. Access to replace this screw isn't that nice however, as it's from the rear of the carb, and there are parts in the way, as always. I think it is the safer option probably.

Of course removing the autochoke assembly makes the job easy, but you may not need to if you are brave (the bendy method), or nimble-fingered (screw out method).

View of PDU in-situ. The red arrow shows the direction it moves when the diaphragm is 'pulled' by vacuum. The green arrow points at the part that actually touches the choke flap linkage. The blue arrow shows the stop that limits its overall movement:


The pin securing it:

Knocking it out/down:

The adjustment screw:

Access to adj screw:



Once you've got the new PDU in and secured with the pin (I think you even get a little 'grippy washer' that fits over the stop too), you will want to set it up for your carb. Don't attach the vac hoses yet, you can set it up without even starting the engine. You just need one longer hose attached to the lower port "A", that you can suck on.

There are two adjustments, the black circular part at the front adjusts the first stage , the little Allen screw mentioned above sets the second stage. Look up the settings required for your engine code, my manual transmission EZ requires 2.8mm and 5.6mm for the two stages. Find some drill bits or similar of the right diameter, measurement is down the front edge of the choke flap, between it and the edge of the barrel.

With a completely cold engine, so that the choke spring holds the flap shut, suck on port "A" with port "B" open to atmosphere. You should see the flap open about the right amount, adjustable by screwing in, or out, the round plastic bit. Once you're happy with that, you can set the second stage by continuing to suck on "A" but now with "B" blocked with a little finger. You will find that the choke flap opens more now. If this second stage needs adjustment it's that little Allen screw round the back. You may struggle to do this while sucking and blocking things, so cheat! Just manually pull the long plastic part of the PDU forwards, as far as it will go. If that's too far you need to screw the Allen screw further in, and vice-versa.

Now you can plumb it all in with the correct vac hoses, and away you go.

See below for a table of the settings for all the various engine codes

Please reply if you've done this by an easier method.

Originally Posted by EZ_Pete

Car / years / engine code(s) / transmission
Pulldown gap, first stage (a), mm
Pulldown gap, second stage (a1), mm

Audi 80 1.6CL / '83-'86 / DT / manual
2.6
5.0
Audi 80 1.6CL / '83-'86 / DT / automatic
2.9
6.0
Audi 80 GL & Coupe 1.8 / '83-'86 / DS/NE / manual
2.6
4.9
Audi 80 GL & Coupe 1.8 / '83-'86 / DS/NE / automatic
2.7
5.1
Audi 100 & Avant 1.8/ '83-'87/ DS / -
2.6
4.9
Golf/Jetta/Scirocco 1.6 / '83-'92 / EW/EZ / manual
2.8
5.6
Golf/Jetta 1.6 / '83-'92 / EW/EZ / automatic
2.9
6.0
Scirocco 1.6 / '83-'92 / EW / automatic
2.9
6.0
Caddy 1.6 / '83-'92 / EW / -
2.8
5.6
Golf/Jetta 1.6 Cat. / '86-'92 / RF / manual
2.5
5.0
Golf/Jetta 1.6 Cat. / '86-'92 / RF / automatic
2.9
4.8
Golf Cabrio/Scirocco 1.8 / '83-'92 / EXZ / manual
2.5
4.9
Golf/Jetta/Synchro 1.8 / '84-'92 / GU / manual
2.5
4.9
Golf/Jetta/Synchro 1.8 / '84-'92 / GU / automatic
2.3
4.7
Scirocco 1.8 / '86-'92 / EXZ / automatic
2.7
5.1
Golf/Jetta 1.8 Cat. / '86-'92 / RH / manual
2.1
4.4
Golf/Jetta 1.8 Cat. / '86-'92 / RH / automatic
2.1
4.4
Passat 1.6 / '83-'88 / DT / manual
2.6
5.0
Passat 1.6 / '83-'88 / DT / automatic
2.9
6.0
Passat 1.8 / '83-'88 / DS / manual
2.6
4.9
Passat 1.8 / '83-'88 / DS / automatic
2.7
5.1

In every case a rather tight tolerance is suggested of +/-0.2mm for the "a" dimension and +/-0.15mm for "a1" Can't really believe it's that critical myself .

[rubjonny]

Vacuum diagrams:

Rear of carb, the tube in the red circle is where the vacuum pipe to the airbox connects:


Front of carb, the tube in the red circle is where the pipe that splits off from the vacuum reservoir green pipe connects:


Vacuum overview:

[EZ_Pete]

Three points to consider that may save a bit of time and effort.

Firstly, before you assume your problem is carburettor related, make sure your ignition components:- Plugs, HT leads, distributor cap, rotor-arm and coil are all working correctly.
With the probable exception of the coil, these are all worth replacing 'as a matter of course' if the car is new to you and has little or no history on paper.

Secondly, if your problem is worse in the morning than later in the day (and it causes the engine to 'cut-out'), your problem may well be carb icing. This is often related to the warm-air feed system, not the carb itself. I've written a couple of threads about this issue: "Talking hot air", and "Mend your Mk2 Driver's airbox thermostat". They are very wordy, and wander off in some random directions, but contain what I hope to be some useful information. Many others have also written splendid stuff on the subject. Lots of handy stuff in here: http://www.clubgti.com/forum/showthread.php?t=124417 too. But this one http://www.clubgti.com/forum/showthread.php?t=123456 is the better recent one for carb icing stuff.

Thirdly, simply to say, don't assume the first fault you find when going through this FAQ to be your only problem. There may well be one or two others .

[max¿mo]

Originally Posted by rubjonny

Temperature Senders:
At the front of the engine block there are 2 temperature senders, red & grey. The red sender controlls the autochoke, the grey controls the inlet manifold preheater.

Is this defo right jonny? I don't have an autochoke anymore so got a coolant flange from a GTI (with two sender slots) and connected a GTI oil cooler, I left the grey sender disconnected after reading this thread http://www.clubgti.co.uk/forum/showthread.php?t=90397
I'm wondering if I've got the right onesm connected now?
Cheers.

[rubjonny]

Some more handy info from spanish mike and ezpete

Originally Posted by Spanish Mike

Hello all readers. There are some of us who learn to do things once, and once is enough.

There are some of us who have to do it again and again, and we learn a little more.

Third time lucky, I hope, and the auto-choke now has a body too hot to touch. Delays caused by the remnants of a broken O ring, which were still floating about and blocking the narrow coolant channel within the inlet manifold. Thus, I suggest and thoroughly recommend that, if the O ring has broken up, and before you replace it and re-assemble, you should flush the whole coolant system, and look to see if broken remnants are flushed out.

I first attempted extracting the remnants from inside the manifold using compressed air. This released a piece of O ring (see Post 82 in this FAQ). I flushed through the manifold with cold water, and all seemed clear of further obstructions. I fitted a new O ring and manifold gasket, and re-assembled.

However, there were still remaining segments of O ring in the manifold and coolant system, and I was soon back with the same problem i.e. the coolant outlet became blocked again, coolant was not reaching the auto-choke and wax-stat, and the idle revs were running high.

I dismantled the manifold again, flushed through with compressed air and water, and re-assembled with another new O ring and gasket. But, coolant began leaking from the gasket. Not sure why, but maybe the O ring and gasket were not seating properly, and/or fragments of broken O ring were creating a blockage, and causing an excessive build-up of coolant pressure upon the gasket.

The third time I removed the manifold, I did not apply compressed air to remove the blockage, as it appeared to me that pushing compressed air into the manifold was not forcing all the O ring remnants out of the manifold, but forcing the remnants against the inner walls. One solution, as rubjonny suggested to me, was to discard the manifold, and fit another.

I also concluded that, although the manifold seemed to be clear of any obstructions, and cold-water flowed through it, the blockage was more likely to occur when the coolant heated up, i.e. the hot coolant expands and softens the rubber fragments of old O ring, and the pressurised coolant forces these fragments to flow towards the narrow outlet and cause a blockage. I managed to poke a thin flexible wire into the outlet, and removed some of these fragments, but access was difficult due to a bend in the channel.

I also concluded, conversely, that when the engine is switched off, and in the process of the manifold cooling down, and the coolant ceasing to flow, some of these rubber fragments would adhere themselves to the manifold walls.

Hopefully, I have finally cleared my manifold of obstructions, but it is impossible to see what is within.

I suggest that (along with rubjonny, and other helpful suggestions from EZ Pete) when the manifold is removed from the engine, it should be soaked in and flushed through with very hot water and detergent before re-fitting. This simple process may not be the final solution. It may only help to loosen up the debris, and may help to extract it, but it will certainly help identify pieces of old O ring still present in the manifold, which are difficult (perhaps too difficult) to remove. I had flushed the manifold with water several times, and the channel sometimes seemed to be clear, but only sometimes. It was evident that as the debris was swimming about within the manifold, and changing location, an intermittent blockage would inevitably occur which would, with the build up of debris, become more permanent.

Again, I also recommend, particularly when an O ring is found to have broken up, the whole coolant system be drained and flushed before re-fitting the manifold. I found a small particle of O ring in the bottom hose of the radiator, which may, along with other remnants, have become trapped in the thermostat, and caused my temperature gauge to rise and fall in an abnormal way (thanks to EZ Pete for this probable explanation).

My thanks to the Forum, especially the members contributing to this FAQ, for helping and guiding me through my problem, and enabling me to return my learning to you.

Originally Posted by EZ_Pete

I decided to look into the coolant channel in the intake manifold, in a very literal sense; so I acquired a spare, and attacked it mercilessly with a hacksaw. This is a view of it upside-down, hedgehog removed.



Rather than take up loads of bandwidth on this thread, I'll just post a few pics of what I found within. The coolant path doesn't go direct from inlet to outlet, but goes down and around the back of the manifold before reaching the outlet pipe.

This image shows the coolant path as it comes in (upside down manifold). Note the narrowness of some areas, and scaling/corrosion making the path smaller still.



And this one shows how it goes right round the back, and a particularly bad bit of 'artery narrowing' This pic shows the manifold the right way up, just to keep you on you toes.



I don't know the history of this manifold, but coolant flow must have been getting rather restricted, and it's easy to see how bits of broken-off o-ring might get stuck in various places . The outlet pipe is quite narrow, but so are lots of other parts of the channel it seems...

So as Mike says above, if you've gone to the trouble of taking off the manifold to change the o-ring, you want to make damn sure that fluid flows freely through it before refitting. If you stick a hosepipe in the o-ring end, you hope to see a good strong flow out of the outlet pipe

If your car's had a chequered history with regard to coolant maintenance, particularly if there's been a leak that someone has neglected to fix, and just topped up with nice hard water instead of a correct mix of corrosion-inhibiting proper coolant, it may be that you have scale/corrosion blocking things up as badly, or worse than in this manifold. I haven't yet tried kettle de-scaling fluid (basically vinegar) to see if it dissolves, but will soon...

Edit: Well the kettle descaler did nothing, even overnight. Some stuff we have at work called Ferrotone Acid Descaler seemed to do the trick though, don't think it's available any more though...

[max¿mo]

Phew!!!
Didn't want to be draining coolant to swap the sender, I only refilled it on friday. I'll check to make sure the hedgehog gets warm with the ignition on tonight just to make sure.

EDIT** It is true, the red is manifold heater, grey autochoke, black temp gauge.

[9olfmk2dale]

exellent info, took mine off and struggled to put it all back, but this thread has helped no end!!!!

[rubjonny]

[rubjonny]

Stage II vacuum control unit:

1. Thermo-pneumatic valve
2. Restrictor
3. Straight connection hose

Stage ll vacuum control unit
1 This device is fitted to 1.6 litre manual gearbox models and 1.8 automatic gearbox models from August 1984 on. Its function is to delay the Stage ll opening slightly whilst the coolant temperature is below 18°C. It achieves this by venting the vacuum hose via the thermo-pneumatic valve and the resistor (see illustration).
2 Check that the straight hose at connection 3 on the thermo-pneumatic valve is not blocked and check the valve itself by blowing through it. It should be open at 18°C and close when the temperature rises above 28°C.

[Spanish Mike]

This is really useful information, and sure to help me find the cure (s).

I have a 1991 Golf CL Auto with Pierburg 2e carb

Problem I have is the engine is revving constantly high at around 2,500rpm, and not dropping back to idle. Reaches normal running temperature, fan cuts in, and just continues to rev.

Thanks for your help.

[Spanish Mike]

Forgot to mention that my carb is a single choke, and the choke flap remains half open with the engine warmed up. Should be fully open, shouldn't it??

[EZ_Pete]

If the choke flap is only half open at full engine temperature you must have a significant problem with the coolant flow through the manifold/waxstat/choke-water-housing; unless the choke flap or the mechanisms that move it are physically sticking/jamming.

If you can keep a finger/hand on the water housing of the autochoke for more than half a second when the engine is at full operating temperature, then the coolant flow is certainly not going well. The waxstat itself may well also have failed, but replacement will only be a partial cure as it will never get hot enough to fully disengage the warm-up cam if the coolant flow is very poor.

Also check the wiring and vacuum pipes associated with the thermotime valve.

[rubjonny]

look at the 3/4 point unit, if it dont retract then you know you got a problem with the ttv, if it does retract you got issues elsewhere, coolant channel o'ring seels a likely suspect since revs are high and the choke flap arnt fully open, though the choke housing may just not be fitted corectly. Check if it hot as above to confirm if it getting good coolant flow

[Spanish Mike]

Thanks Pete and Jonny. I am fumbling through it all despite not being very tech minded. I have checked the waxstat by taking it off and placing it in hot water. The pin expanded out so I guess that is working OK. I have also dismantled the auto choke and checked the heater which expands the spring coil, and that works OK. Tomorrow I shall re-assemble and start the engine to see if the choke housing gets hot. I shall also look at the ttv and the 3/4 point unit - not sure what I'm looking for here, but I'll keep you posted. I must also look at the red and grey temperature senders at the front of the engine block, and make sure the Stage 2 vacuum control unit tubes are clear. How do I test the thermotime valve? Step by step.....your help really appreciated.

[Spanish Mike]

Thanks Pete and Jonny. I am fumbling through it all despite not being very tech minded. I have checked the waxstat by taking it off and placing it in hot water. The pin expanded out so I guess that is working OK. I have also dismantled the auto choke and checked the heater which expands the spring coil, and that works OK. Tomorrow I shall re-assemble and start the engine to see if the choke housing gets hot. I shall also look at the ttv and the 3/4 point unit - not sure what I'm looking for here, but I'll keep you posted. I must also look at the red and grey temperature senders at the front of the engine block, and make sure the Stage 2 vacuum control unit tubes are clear. How do I test the thermotime valve? Step by step.....your help really appreciated.

[rubjonny]

1st thing check the plunger on the 3/4 point unit. with the engine off it should be extended 14mm, then once the engine is started it should retract after a few seconds to 8mm. if it does this then the TTV should be fine. Another check is if you turn the key 1 click you should hear the 2 electrical valves behind the carb click

[Spanish Mike]

Yes, the plunger operates as you say it should. I also hear the click of the valves. Therefore, I have eliminated the auto choke, the waxstat, the 3/4 point unit and the two electrical valves, although perhaps the click is only one of the valves working. The vacuum tubes look OK - no sign of fractures. When I dismantled the auto choke cover, the thin flat circular washer, which seals the water, broke as it had become brittle. When I have overcome this, I shall warm up the engine and see if the choke housing gets hot. If the choke housing does not get hot, I need to look further....with your help. Thanks a lot.

[EZ_Pete]

That thin flat washer you've broken is actually the ground-connection for the autochoke electrical heater. It's meant to connect the metal water housing to one of the fixing screws that hold the plastic intermediate mounting to the carb body itself. Recently discovered this myself... You can get round it by attaching an earth lead from one of the three 'adjustment' screws that loosen off to allow rotation of the water housing. May have to clean up some of the metal surfaces to get a good connection though, I did.

I'll take a photo tomorrow if this is as clear as mud in words . It's unlikely to be relevant to your current problem, because this electrical heater turns off when the coolant at the thermoswitch housing gets to about 55°C or thereabouts anyway, it's the coolant heating in the autochoke housing that's really critical to the choke flap opening fully.

I would think you are looking at a coolant o-ring problem, having eliminated TTV. Could be a partially failed waxstat still though. Did it pass the test suggested in Haynes etc? When cold (room temp), if you push on the little pin with a force of 30 or 40 Newtons, it should go no further in than 2mm proud of the front face of the mounting flange.

Have a look at this

[Spanish Mike]

That's interesting. I thought the thin flat washer was a water seal I didn't realise the intermediate mounting is plastic - looks metal to me, but you know more than me. Therefore, you say the washer is not plastic but made of conductive material. Yes, as you say, it looks increasingly like coolant O ring problem, but I have yet to check the grey temperature sender at the front of the engine block, if that has anything to do with the problem. It has just started to snow here in sunny Spain but tomorrow I hope to start up the engine again, get it up to normal temp. and see how hot the auto choke housing gets.
Thanks, Pete.

[Spanish Mike]

Forgot to mention - I was able, with some pressure, to push the pin of the Waxstat back in, but it did not go in further than about 2mm proud of the mounting flange. Therefore I am assuming this is not the problem. Also, the accelerator pedal is a little stiff, but it always has been. But the pedal does not spring back when you take your foot off. I wonder if there is a problem in the linkages, bearing in mind the car is an automatic, and it has accelerator linkages on both sides of the carb, or is it just not springing back because the choke flap is half open.....let me see what tomorrow brings.

[Spanish Mike]

Should mention too, while I think of it, that I read on another site, that the problem could be a blockage in the brass port at the rear of the carb. There is a tiny hole (0.5mm) controlling the vacuum, and it gets blocked. Can't tell you any more, but worth bearing in mind before I take off the manifold, and replace the O ring as a last resort. Mike

[Spanish Mike]

Not much progress today. Started engine, and water was running out of the auto choke housing. I guess that flat washer between the housing and the top cover is needed as a water seal. I wonder if EZ Pete is talking about another washer. I must seal the leak. Mike

[rubjonny]

looking at etka theres 2 washers, a thin one under the big bolt in the middel and another large one round the outer edge of the heater. Unfortunatly these arnt available from VW anymore! The unit is 77+VAT from VW, I think this is the part you need from GSF?
18229 CHOKE COVER ASSEMBLY G2 1.6 / 1.8 8/83 >10/91 57.50