Pierburg 2E3 Rebuild and Adjustments

I wanted to do a complete rebuild of the Pierburg 2E3 carburettor on the van to make sure it’s running as it should. Coming at this as a complete novice (and worrying i’d damage my good carb) I decided to buy a second unit off eBay so I could learn how it all works. In the following video I rebuild the “test” carb using a kit from Brickwerks and make the adjustments outlined in the PDF resources below.

If you have an early model 2E3 you may need an additional 13mm diaphragm.

PDF Resources


Video Transcript


This is the Pierburg 2E3 for the Volkswagen T25. I’ve completely stripped this down and in this video I’m going to use a carb rebuild kit to put everything back together.

For reference I’m using the workshop manual for the 2E3, I’m using the Transporter Construction and Operation for the water cooled boxer engine, the Pierburg 2E3 adjustments and settings, and the PDF by CJH on the Club 80-90 forum. He’s put together this guide using the same documents we’ve got there so I’ll go through this.

And finally the Solex and Pierburg Haynes manual which has got some really interesting information in.

I bought this version from ebay because I need to rebuild the one on my van and I didn’t want to break it at all so I’m using this as a testbed to do the rebuild kit so I can learn everything about the carb before doing anything damaging to my own one.

Version Identification

So this version of the 2E3 is specific to the Volkswagen T25. There’s lots of different versions and configurations of the Pierburg. You’ll see if you look on ebay for different versions of it you’ll see the different entry points and exit points and however it all works inside. So if you’re looking to get one for your own van you need to get one with the number 025 129 015 which is stamped here. What some will have is a letter after, this one doesn’t which means it’s a really early version of the Pierburg. The other letters are A, which is for the automatic gearbox ones and the later ones are J and H.

I’ve actually got a J, sorry a H version over here. I’ll just put some gloves on as it’s very dirty. I got this other one in a job lot and it looks like the previous owner had a fight with it so it’s in a state. So there you go, you see how dirty it is. And the difference is you see, this is the H version, you’ve got the bent part here and you’ve got this little filter here and there’s also a gap, a little flap within the actual choke flap here which can open if you poke it. But this one I’ve got here did look like this when I got it off ebay and I’ve cleaned it using white spirit and Wynn’s carb cleaner, I’ll just get that. Some Wynn’s carb cleaner sprayed it all in there in the vents and everything and use white spirit and a paintbrush just jabbing it in and what that did is just clean it all up so got rid of all this gunk you see here which is pretty horrific when you first open it up.

Rebuild Kit

I’m going to be using the Brickwerks rebuild kit. That gives you everything you need, it’s got gaskets and seals and different parts. You may need a different diaphragm depending on the version you have and I’ll show you how to check for that later on. You’ll see this one is a shorter version here and later models had this longer one.

So in this video I’m going to use the Brickwerks rebuild kit along with these parts that I’ve removed from the carburettor. You’ll see that there’s a big array of parts here so you’ve got the float and float needle here, the jets, the mixture screw, the accelerator pump, and then you have the diaphragms so this is the choke pull down unit, the secondary pull down unit, secondary throttle pull down unit and then the automatic choke parts here and here. And the idle control valve and the little heater.


So I’m going to start with fitting the jets to the top half of the carb. It just splits in two, like so, this is the bottom half. I’m just going to move that out the way for now. So turning it upside down we have three jets here that are removable, there’s others that can’t. So, the first one is the primary one which is this one and that’s got the number 102.5 on it if you ever need to get a replacement one and it goes on this side here near the primary venturi. So I’m going to slightly screw those in for now. The secondary one is number 110 and that goes on here. And then the air corrector jet goes here. Now it’s important to use a screwdriver that fills essentially all of the space there. Because these are made of brass they are very, very soft. You don’t want to damage them as you do it. There we go. There we go. So that’s the jets fitted.

Float and Needle Valve

The next thing I’m going to fit is the float needle and float. So what happens is fuel comes into the carb here from the fuel pump and it will exit here going back to the fuel tank. What the float needle does is allow fuel to come through this gap down into the float bowl. If the needle is completely shut, all the way in, no fuel will come down it will just go straight back to the fuel tank there. And this is the actual float. So depending on the level of fuel that is in the float bowl, this will move up and down and push the needle up and seal it off. OK, so the float needle I got in the Brickwerks kit is this one here and this is the original. You’ll see this one fits nicely in there and just drops straight out. The Brickwerks one however gets stuck, so that’s just no good so I’m not going to use that. I’m actually going to re-use the original as it seems to be in good nick. Seems to be doing what it should, the rubber part at the end is in good nick there. So what it has is a little metal clip here so that goes on the end, I’ll just try and get that on. OK, and that hooks through this gap in the float there. So you’ll see it secures it against that. OK, there’s a pin that secures the float in place and that just needs tapping across, so I’ll just line that up. OK, just make sure that’s lined up. OK, so you’ll see how the float moves free there and it controls the float needle. You can test this by sucking on this pipe and putting your finger over here, and hopefully, if it’s all working you won’t be able to pull anything through. OK, so we need to take a measurement here. In the setting guide there’s this information to cut out this template and that will allow you to work out that the float is working at the right level. It gives you measurements between 28-30 mms but that’s wrong according to the Haynes manual.

The Haynes manual gives that measurement for many of the vehicles in here like you’ve got the Volkswagen Polos or the Vauxhall cavaliers. But for the Volkswagen Transporter which we’ve got, obviously, the float level needs to be between 27.5 mm plus minus one mm. So the template i’ve created is between 26.5 and 28.5. So as long as it fits between these two measurements we should be fine.

So i’ll hold it at 30 degrees roughly and position this over it and you’ll see it’s just under 28.5 and just over 26.5 so as long as it’s under that measurement which it appears to be that should be fine because we’ve got that tolerance of one mm.

Mixture Screw

Onto the bottom half of the carb i’m going to fit the mixture screw for a start. It looks like this. The Rebuild kit comes with another o-ring there which you can fit on. So the mixture screw goes in this hole here and what that does is control how much CO2 to fuel ratio goes into the carb. When removing the mixture screw, what I did was screwed it all the way in but counted how many turns it took to do that. Because I bought the carb off ebay I have no idea whether that’s actually a good setting for that to be at but that’s what I’m going to return to. So what I’m going to do is screw it all the way in and then screw it back out two and three quarter turns because that’s what it came with. It takes a while to screw in, there we go. So I’ve reached the bottom now so I’m going to unscrew it, one, two, and then three quarters. If I actually put this on the van I’ll be able to see what kind of setting that is and make adjustments then.

Second Stage Throttle Adjustments

OK, so whilst everything is off i’m going to check the second stage mechanism to make sure it works how it should do. So the is the primary throttle plate here, as you accelerate, put your foot down on the pedal it pulls this open. What it also does at the same time is activate this cam here which connects to the accelerator pump which i’ll be fitting in a bit. So as that’s turned more air can come into the engine and more fuel is pumped into the engine through the accelerator pump there. What also happens, you’ll see here, the second venturi cannot open up to a certain point because it is locked by this lever here. So as I accelerate hard going up to fully open you’ll see now that can open. It allows you to go even faster in the van. What i’m going to check now is the measurement here because what you don’t want to happen is there to be any movement in this section here, and you’ll see there is actually on this one. I had a problem with the carburettor on my van which meant that I would hit a certain speed and this second venturi would stay open. Which caused the revs to stay high. It wouldn’t go down again until i switched off the engine and restarted because the vacuum was keeping this open. It’s go the same problem with this carb actually. The measurement between this U channel here needs to be 0.4 mm on both sides. You can see because there is a bigger gap it’s actually allowing that to move open when it shouldn’t do. What we need to do is use a feeler gauge, so 0.4 feeler gauge and check the gap between that. So that side is OK and we need to squeeze that one in. We need to use a pair of pliers just to squeeze these together slightly.

The second measurement we have to take at this point is this screw here. What we need to do is jam the primary venturi open, so this can move about a little bit, and use an elastic band just to keep the second stage part shut. So you’ll see there is a little bit of resistance there but the elastic band is keeping that shut. What we want that to do, this screw, i’m going to put a bit of paper under there. I’m following CJH’s recommendation here for this process. What that needs to do is go under there and just needs to grip it, which it is actually doing at the moment. What i’m going to do is unscrew it slightly just to see what it’s like without. So you’ll see now it’s unscrewed it’s not gripping the paper. Just going to keep moving that till it grips. OK so it’s just gripping the paper. So now it’s gripping the paper just turn it one extra quarter, just like that. There we go, that adjustment is fine now. It’s nice and sturdy now, there’s not much slack in there at all.

Part-load Enrichment Valve

The next part i’m going to fit is the part load enrichment valve, that goes here on this side of the carb. What you’ll get in the kit is two of these red parts, gaskets?, whatever they’re called. This one has to go through this section here, and you put the other one on. There’s this tiny little bit that goes on the end there which has got an o-ring on it, and that needs fitting onto this here. Give it a good push, there we go. I’m just going to tap it slightly with a hammer. Make sure that’s on, OK. Now there’s a spring which works against this part to close the valve, depending on the pressure inside the carb this moves in and out allowing more fuel in. So the spring fits there and fits over that part there. So that’s fitted to that side, there’s also another gasket there and there’s two screws that secure it in place.  You can see how those holes line up. So that’s the part load enrichment valve fitted with the new gaskets.

Accelerator Pump

I’m now going to fit the accelerator pump. At the start of the video I mentioned that you may need a different sized diaphragm depending on the model of carburettor you’ve got. This is the accelerator pump outer part, depending on the size of this dictates what size diaphragm you need. You see this is the long one, it’s too long for this section so I had to buy another part like this which is a smaller one. I think it’s 13 mm. The Brickwerks kit comes with the 19 mm anyway so if you’ve got a later model carburettor you should be fine. I think these are only £4 for an extra one. Also in the beginning of the video, not sure if I mentioned it or not, but I Bought the kit from Brickwerks for a specific reason and that’s because I previously purchased a kit from ebay, but the quality of the parts in the kit are just not up to scratch and an example of that is these diaphragms. This is the original diaphragm that was in the carburettor, this is the Brickwerks one, and this is the one from another ebay kit. Now CJH pointed this out in his PDF so it’s down to him that I actually checked this, i’ll show you the difference. The original, so the strength of that ball bearing is really quite strong. The Brickwerks kit, not at strong but that might be gunked up but it’s still pretty strong. And this is the ebay kit, and there’s just nothing to that spring. So what that will do is actually affect the amount of fuel coming into the carburettor and affect performance so just don’t bother. To fit the accelerator pump what we have is this little red thing, that goes in the hole. There’s this radioactive warning sign piece of metal which goes on there, then the spring, then the diaphragm. Make sure it’s lined up this way because there’s a little peg inside the pump which lines up there and fits on top. There’s just four screws that just go in and hold that in place. So there we go, that’s the accelerator pump in place. You’ll see now as you turn the throttle the cam here moves the accelerator pump and the spring moves against it.

Pump Injector

Now that the accelerator pump is in place i’m going to fit the pump injector. That squirts fuel straight into the primary venturi here so it just sits like that. There’s an o-ring which comes in the pack that goes on the end and there’s a little red filter, this doesn’t come in the rebuild kit so try and use the one you’ve already got. Once those are on you can just slot it into the section here, it just goes in by pushing it down. Normally i’d want pointing this way but i’m actually going to turn it around so it’s squirting this way because what i’m going to do is put some fuel in the float here, the float bowl, and then use this syringe to measure how much fuel is coming out in each stroke. If it’s too much or too little, what I can do is adjust this screw here on this cam which will adjust how much fuel is coming in every time the accelerator is pressed down. I’ll just do that now, i’m going to put some fuel in there. So now i’ve put the fuel in there and getting high off the fumes, what i’m going to do is turn the accelerator, the throttle, five times. Each time I do it, it’s going to be three seconds with a one second gap between it. What i’m looking for is a measurement of 1.35 ml per stroke. By doing it five times I want this to be 6.75 ml. The mark we’re looking at is just there. I’ll get a knife or something to make a mark on. So i’ll just make a mark there. So i’ve scratched it to the mark that we want. I’ve squirted some through for a start just to make sure the fuel is actually coming through, so now i’m going to position this here and start turning the throttle. One, two three. One, two three. One, two three. One, two three. One, two three. OK, so that gives me five, five mm so it’s not enough. So what i’m going to have to do is adjust the cam to give me slightly more per stroke. So i’ve emptied the fuel out of the carb here so I don’t spill it everywhere which i’ve already done as you can see and what I want to do is adjust this screw here because this cam controls how much fuel goes into the carburettor. I’ve already unscrewed it and you’ll see it moves left and right. When it’s over this side it’s already primed slightly so it’s already pushed in a slight amount, you’re going to get less fuel coming through. So what I want to do is push it all the way to that side, no I can’t actually move it any further so that might by the maximum I can move this. I’m going to screw it up and we’ll try again. I’ve actually pushed this in a bit further, just to make sure it’s really solidly in because I think a bit of air was coming in here affecting how much was coming through. So i’m going to try again. So, we’re at the perfect amount now so it’s 6.75 which is exactly the amount we want. It’s 1.35 ml per stroke coming out here. Now we know enough fuel is coming out of the pump injector we just need to turn it around so it’s actually pointing towards the primary venturi here. We want the squirt to go straight down that little nick there, making sure it’s pushed right down which takes a bit of force. I’m just going to test it, I think there’s a little bit of fuel left in there. Yeah, so you can see it squirted straight down there making a mess of my top.


OK, so back onto the top half of the carb. What i’m going to do now is fit the automatic choke mechanism. That’s what this is here. What that does is control this flap. So on a cold day this will be nearly closed making sure it chokes the amount of air coming into the engine so it doesn’t die. As the engine slowly warms up, this flap will slowly open up until it’s fully open. So that’s controlled by this mechanism here, you’ll see this lever on the side. What this does is attach to this part which has the coil inside. This is connected to the 12V ignition live. As this heats up this coil starts moving out. So you’ll see it move out like that and what that will do in turn is turn this lever which will open up the flap here. As well as the 12V on this it’s connected to the water-cooled system. So the hot coolant will go through there as well as the electrical heater. That will turn out and that will open up the choke flap.

Pull-Down Unit

So for a start i’m going to fit the choke pull down unit, that fits onto the carburettor here. And what that does is the vacuum comes from this pipe to the bottom end of the carburettor and the vacuum sucks this in, this section here. What that will do is control a part of the automatic choke there, so it will prevent it going too far. I’ll show you how that works once that’s fitted. This section goes in here, the little hole. You’ll see it just clips in. Just push that into position there. Make sure you can see through that hole there because there is a roll pin and that just needs hammering through. Best to do it from the bottom actually so you don’t damage the jets when you are doing this. Completely jabbed into my top there. So now that’s fixed into position, there’s an adjustment screw here which we might have to adjust later, i’ll show you that shortly. The vacuum pipe that goes down to the bottom, what that has inside it, if you’re lucky, is a this little restrictor valve. This carb didn’t come with one of these, it wasn’t in the pipe. This one is from the one from the job lot. I pulled this out just to show you. What that does, it’s got a really tiny hole, probably 0.1mm or 0.2mm and that just stops the strong vacuum pulling through and slapping this vacuum unit shut, damaging the diagram. That’s the only reason that’s in there so if you don’t have one I don’t think it’s fatal to the operation, but it’s good to have if you do.


Now i’m going to fit the automatic choke, and that attaches to the three screws here. First, there’s a little cam inside this part which controls the flap and there’s a lever that attaches to that so you just need to put it in there like that and it will hook in. You can see how that controls the flap. So that attaches to this white bit here. So that goes in like that and there’s a tiny washer, and a clip that holds this in place. I’ll try and fit that while it’s here. So that holds the lever onto the automatic choke. Just going to line up those holes. There’s three screws which secure this to that section there. So that’s now secure on there. You’ll see how this lever now uses that mechanism to control the choke flap. I’m going to put the two halves together now so then I can make measurements on the choke flap. I’m using the gasket that comes with the Brickwerks kit. I’m fitting these gaskets dry in this demonstration but when you’re fitting it yourself, if you’re going to be moving it on and off a lot of the time the dry ones can get stuck together so you can lubricate it with petroleum jelly or grease and that will stop it sticking but still create the seal. When fitting the two halves together you’ll see this pipe here, that actually goes into that gap. As long as you get that lined up the rest of the carb slots in where it should do like so.


So i’ve put the two pieces together, the two halves of the carb and then i’ve used an elastic band just to hold the two pieces together. What happens is the fast idle cam here, this screw actually pushes against this section it will push it apart, that’s why i’m holding it together. (I forgot about the 5 screws which hold the carb together). There’s also another elastic band across here, and that’s to pull the automatic choke this way as if it was being held by the coil. The measurement we want to take here is the front of the choke flap so we want to make sure this screw here is on the very top of there and you’ll see the choke flap is now completely closed. What we need to do is put pressure on the choke pull down unit here by pushing in on this section. There’s a little screw here so if I need to make adjustments I can do with an allen key. I’m just going to push into there. You’ll see the choke flap now moves. The space for this carb is 3.3mm, i’ve got this drill bit which is actually 3.3mm width. That’s the perfect size for me to measure the front of there when i’m pushing in. Other models of the carb, it’s 2.5mm so just check you’ve got the right measurement for your own one. I’m going to push in here and put that in the front, it’s slightly too small. So i’m going to use the allen key to adjust the screw here which will enlarge or make that smaller. I want to make it larger so i’m going to screw it out, anti-clockwise. Just going to try again. You’ll see now its way too big. I’m just going to screw it back in slightly, You can suck on the pipe connected to the pull down unit but i’m just going to use the pressure on this end here. There we go, that’s the right measurement for that.

Automatic Choke

I’m now going to fit the heating element to the automatic choke, there’s a square hole here we just need to line that up with the lever when we’re fitting it just to make sure that’s attached, that will control the choke there. There are three screws and they just go in here. Before tightening the screws i’m just going to line up this mark here, you can twist this part here so that they line up. If you are taking this off your own van make a mark of where it currently is because it’s probably been put in that position for a reason so try and get it back to the position you had previously. Another good tip by CJH is to keep this on the van when you’re taking the carb off because otherwise you’re going to have to unplug the coolant pipes here and you’re going to get coolant everywhere. By unscrewing those three sections and knowing exactly where that is you can take the carb off without messing with the coolant circuit there. I’m just going to screw these and secure those in place. There we go.

Second Stage Throttle Pull-Down Unit

Next i’m going to fit the second stage throttle pull down unit, again this has got a diaphragm in there which acts with the vacuum sucking in through here and pulling this section up. Just move the top half out of the way. This little elbow here clips onto that part and it screws in there. What that does is pull upwards, pulling against this here. Of course it won’t do anything until a certain stage of the throttle. So there you go, that will pull against this. It’s quacking at me. So the elbow just sits on that part there. As I explained, that pulls upwards and then opens the secondary throttle plate here. The vacuum pipe for this part attaches into this section and then bends backwards on itself into this here. There we go.

Idle Cut-Off Valve

The next part i’m going to fit is the idle cut off valve which looks like this. That fits into the carb here. What that does is when you switch the engine off this doesn’t get any power anymore and so there’s a pin which shoots out and that cuts off the fuel going into the carb and stops the engine running on. You can test if this is working OK by using a 9V battery which i’ll do now. Connect the positive to the pin at the back and then i’m going to earth at the front here where this metal part is. So it clicks on and off. So that pin is moving backwards when I do that. The o-ring that was with the original one is all perished as you see here so i’ve used two o-rings in here to act as a seal, i’ve also used some PTFE tape, thread seal tape so we get a proper seal in that. That just screws in so i’ll just do that now. There we go, so that’s in position now.


The next part i’m going to fit is the 12V heater, it looks like this. That fits to this part of the carb here just under the idle cut off valve. What that does is heats up this section of the carb making sure it runs OK in cold weather conditions. It’s connected to the thermally switched 12V system as well as the small heater that’s in the manifold. The hedgehog looking thing. These two things, once the coolant system gets up to a certain temperature, these two things switch off because they’re no longer needed as the carb is up to a certain temperature already. That just fits here and is screwed in place with one screw. That’s in position now.

Vacuum Pipe

Now that the idle cut off valve and the heater is in place i’m going to fit the vacuum pipe to the pull down unit, that connects here. As I mentioned earlier, there’s a small, tiny valve that will go in that pipe, i’m not going to fit it now but that would normally sit in there restricting the actual vacuum that hits that. That just connects into that part there. On the rear of the carburettor, or the front I suppose, facing the front of the van are these two other vacuum pipes here, tow vacuum connections. This one runs to the air box, in the UK you don’t really need that so mine was actually bunged off on the one on my van and it actually ran better when it was bunged off so that’s something to think about. This is the vacuum pipe to the distributor, this one is important, you must have that one connected.

Fuel Filter

The next part i’m going to fit is the fuel filter, this goes into the inlet pipe here. This is what the original one looks like, so i’m going to re-use this and the reason is because I bought this one off ebay, you’ll see it’s very white, and it was already split when I got it and the quality of this is so flimsy I don’t think it will stand up to it’s job for too long so the best thing to do is re-use this reinforced filter that comes with the carb. You’ll notice there’s two little pegs here, don’t know if you can see that, that allows you to take it out by screwing in slightly and then pulling it out. Fitting it is dead easy, you just literally push it in place. There we go, so you’ll see that is now fitted there. That will filter out any particles and bad bits coming from any other part of the fuel system going into the carburettor there.

Gaskets and Manifold Spacer

The last part of the rebuild kit, you get this gasket. What this ones does is it goes between the bottom, fits over there, and the manifold spacer, which is this one. So that goes there. This is really important to have, the spacer. It lifts the carb away from the manifold, without that you’re going to get this lever hitting the manifold and you won’t be able to get full speed, it’s going to affect the performance of the carb. When you’re attaching it, make sure you’ve got that in place. The rebuild kit doesn’t come with one between the spacer and the manifold so i’ve actually cut this one out of gasket paper, this is 0.4mm gasket paper. I just used a pencil to outline it and then cut it out to the same size. That will fit between there. It’s imortant to have all these gaskets in place because, due to the nature of the carb, it is vacuum based so any air leaks are going to affect the performance of this. The carb that I had on my van didn’t have any gaskets between the manifold so I replaced those but it unearthed lots of other issues with the carb because there was other air leaks and mis-adjustments which i’m now addressing. Hopefully, now i’ve done this one I can do the one on my van and that’s the end of that.

6 thoughts on “Pierburg 2E3 Rebuild and Adjustments

  1. Great stuff. Thank you for making this. Hopefully I’ll have the courage to do mine.
    Did you install the one featured in the video to your van or was it just a test run?

    My van has very poor mileage and when going in a turnabout it chokes for a sec. My friend suggested that it’s something with the float. Seeing your video made think of rebuilding a spare carb that I have and then replace it with the one I have in my van. Do you think that a good idea ?
    Many thanks.


    1. Hi Itamar. Yes, it ran really well. I had it on the van whilst rebuilding my original. I used the Bromyard set up instructions (check the downloads section for it) to get the timing and adjustments right.

      If you can get access to a spare carb, I think that’s a good idea. You can the learn how it all works and be able to identify any issues in the future.




  2. Hi James,

    I’m just doing this at the moment – the setting for the choke flap, I’ve got and e3H carb, is the setting you use for this version or should I be doing something else. I had a quick look at the pdfs but couldn’t find anything specific to the H version. Thanks


  3. James, I’ve decided to follow in your footsteps and bought myself a 2ndhand 2E3 carb for my T25. Vendor claims it runs fine so albeit a bit more expensive than I wanted to pay, at least with 2 working carbs I should be able to de-risk the overhauls of both of them. My current one runs fine, but I’m experiencing low fuel mileage and higher hot idle revs, so thought I’d give this a try based on your worthy efforts! If it all goes well, then I’ll just sell the refurbed 2ndhand carb.


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