Pierburg 2E2 stuck 3 point unit

Hi chaps. it's been a while since I've visited but I've recently bought a 1985 Scirocco GTX which has a temperamental Pierburg 2e2 carburettor.
When driving, the idle sticks at around 3000 rpm until I open the bonnet and VERY slightly push on the screwy bit that the 3 point unit pushes on, after which it settles (quickly and by itself) down to about 1000 rpm. (see picture)
I've oiled the pin of the 3 point unit a few times but it seems to keep happening.


What gives? Thanks in advance

 

the hoses are a bit frayed but I think they are ok.
I'm not sure which valves you mean, do you have a diagram/picture?

 

The pink hoses in this image are the favourites to cause this problem if any of them aren't airtight:



Worth also checking the airbox-connected hose, from the stub with the red ring around it in the image.

Sorry; all the hardest to reach/see ones!

The electrical bits John mentioned are the TTV (11 in image, looks like you've had to repair the wiring to that before?), and the over-run cutoff solenoid valve, 12 in the image.
No.12 should click immediately the ignition is switched on, the TTV may take a few seconds if it's cold out, and the click may not be as obvious.
In my experience, both of these devices are themselves very reliable, as long as they are getting 12V when ignition is on.

 

Still having trouble wit te 3-point unit retracting too slow meaning the throttle sticks on.
I've replaced all vac hoses and when taking power away from the TTV the car first revs up and then dies on ignition meaning they must work right?

I've also changed to waxstat without effect.

I have a Pierburg 2e2 from my 1.6 golf which I might try, will I run into any problems when I run it on my 1.8 scirocco?

 

There's another thing to try/check before you chuck in the towel with this carb.

The vac hose that 'drives' the 3-point unit at idle is the 'pink' one coming off the base of the carb at the back (connected next-door to the red-ringed stub in the above pic).

Now inside that pipe stub on the carb there's a restrictor which has a very small diameter, around 0.5mm if memory serves. It's possible that this has become clogged up, reducing the vacuum signal that the 3-point unit is getting.

It won't be straightforward to check that this is clear with the carb in situ, but could be your problem, so well worth having a go. Maybe find a drill bit or piece of thin wire of 0.5mm dia and just see if you can poke it in there. If you use a drill bit, try not to snap it off in the hole.


It's possible that the 3-point-unit's diaphragm has become leaky, or even that the o-rings which seal the adjuster on the back have started leaking significantly, but I'd certainly try the above before anything else.

Good luck.

 

I've swapped the 3-point unit and the pin retracts completely, flush with the base of the round thing, is that supposed to happen?

The idle is now at 500 rpm which is a bit of a problem, i've tried adjusting the nut at the back of the 3-point unit wihtout any success. Any advice on the idle?

 

Only momentarily at switch-off. Or on the overrun (revs>1200) if you have the relevant relay in your fusebox.

Sure you've got the vac pipes all plumbed as per the diagram above? And both two-way electrical connectors on at the back?

If the overrun/cutoff valve is unpowered, that would explain why it's fully retracted.

Edit: The way it achieves the 3 plunger positions is as follows:-

Fully extended - no 'suck' on either vac connection, so the internal spring pushes it all the way out. Only happens if engine is off, or engine running but TTV is open (cold) causing the vac feed to the lower 3PU port to be 'spoiled' via the t-piece in the pink hoses.

Idle positon - vacuum on lower vac port (via pink hose), but upper vac port open to atmosphere via brown hose, open (12V powered) over-run/cutoff valve and blue and red hoses. The red hose connection at the top of the carb is effectively 'open to atmosphere' but filtered by your airfilter rather than grotty air.

Fully retracted - vacuum on lower port, and upper port blocked by a closed (unpowered) over-run/cutoff valve. Happens when ignition goes off and/or - if the over-run cutoff relay is fitted in the fusebox - when foot off acc pedal and revs>1200. In the latter case the relay temporarily depowers the overrun/cutoff valve, until the revs drop below 1200.

Very soon after the engine stops, it will revert to fully extended again, as the vacuum supply has gone.

 

All vac hoses are in and the electrical connectors on the TTV on the sides are in, yet the pin retracts fully, i think it did this on the other carb aswell but I'm not sure. On that carb I had put a few washers between the waxstat and the carb to get it to idle higher but that doesn't seem to work on the new carb.
Any other reason the pin would retract fully?

 

You changed the 3PU or the whole carb?

I've edited some description of what conditions on which vac ports (and power/no power on over-run/cutoff solenoid valve) give rise to the 3 positions, to my previous post. If the pink/blue/red/brown vac hoses are all correctly plumbed, I think your overrun/cutoff valve isn't getting 12V. Have you measured this at the connector to item 12 in the above image, with ignition on?

 

Just changed the 3PU, I'll check for 12v now but as I said, i think it retracted fully on the old carb from the golf as well

 

If you don't find that 12V, have a look at your fusebox, see if you can find a relay with 61 written on the end facing you (or maybe 10, judging by a pic I just found in an old VW book). It may well be above the main 12 positions that are easily seen through the little removable cover, position 22 I think on an '85 car, asssuming that Sciroccos use the same positions as the equivalent-age Golf:



If that is there, but not working, or not making good contact in its socket, it may explain why this is happening.

Also check fuses 17 and 18 (both 10A), again assuming the numbering is same on rocco/golf of the same age.

 

If you do find 12V between the connector pins, plug it back in, start the engine and let it warm up for a few minutes, then try disconnecting the upper vac hose from the 3PU (the brown-coloured one in the diagram of post 4). The 3PU if retracted fully should now move out to the idling 8.5mm-ish position.

This would prove that the 3PU itself is OK, and that the problem is something to do with the overrun/cutoff valve or what it's being told to do by the electrics.

 

The relay 61 is there, and I get 0.10v on one connector and nothing on the other going to the carb.

Does that mean the relay is faulty? I've never had to replace a relay so I don't know how to remove it, is there a part number for the relay so I can order it?

 

Did you check the fuses I mentioned?

I would certainly expect to find 12V on the (carb connector) pin with the black wire going to it, with ignition on. Check this with your red meter probe on the pin, the black meter probe on something that's definitely grounded. If that's not 12V there's no chance of things working.

What the relay does is to make or break the return connection (the brown/black wire at the carb connector), trouble is I don't know whether with just ignition on, but engine not running, it will be made or not made (my car doesn't have the relay, many don't). Try it with engine running, and idling at a speed definitely lower than 1200, measuring between the carb connector pins with your meter probes, if you can get them both in there (try not to short the probes together!). That should definitely show 12V if relay and wiring is all OK.


Did you find the relay in the expected location, position 22?

It should just pull out, though it may require holding the bit it plugs into and a bit of effort.

See whether wiggling it in its socket changes anything.

Part number should be written on one side of it, expect something like 811 919 096F.

BUT, it may not be bust, it might just be a dirty/corroded contact, which you may be able to spot if you get it out.

Will be busy for the next 2 or 3 hours but good luck!

 

My fusebox doesn't have positions 13 to 24 but there is a single socket for the relay near position 18 on the diagram

I checked the two way elec connectors with black probe grounded on chasis and the top on that you can clearly see in the photo gets 12v but the bottom one gets nothing. I've checked the relay and it seems clean but can't tell if it's faulty or not.

The 10 amp fuses are fine

 

Was there meant to be a photo in your last post?

Anyway, here's a way to check that the system works, without using the relay. Look at the pins of the relay (with it unplugged, obviously), and identify two which are labelled "31" and "SAS". Now work out which two positions in the socket these go into, check this a few times 'til you're sure, maybe mark them with tippex on the socket.. Then stick a piece of wire into these socket positions to connect them together.

If you can see the wires coming out of the back of the socket, this should link together the brown one and the brown/black one.

Then see what the 3PU does. This will make your car just like mine, and many others that don't have this relay fitted, no great loss, I think.

 

I meant the photo from the first post.

I've put a wire between SAS and 31 and it now idles at 2200 rpm when warm, the pin sticks out about half way. Do I maybe need to adjust the screw to get a lower idle speed now?

Thanks for the help

 

Yay, progress!

Yeah, try the adjustment on the back of the 3PU now to bring it down to 950ish. If you run out of adjustment you may have to also move the headless screw that the plunger pushes on, but I doubt it, unless someone has tinkered with it before.



Edit: so were you saying that the TTV, the round valve with the bodged wiring, isn't getting 12V with ignition on?