Pierburg 2E3 choke

[CJH]

Well this may or may not be the cause of my 'dead spot' (it's worse than a flat spot), but it certainly needs attending to. The cam seems to be on its lowest setting, and there's what looks like a gap between the cam and the lever. I'll adjust it to take up the slack in the lever and see what that does to the dead spot.

[CJH]

I adjusted the cam all the way over to the opposite extreme, and that seems to have fixed the dead spot. I can once again pull away smoothly without stalling now.

So I guess I'll just run with this carb now to see how the two nylon parts fare in use.

[itchyfeet]

I adjusted the cam all the way over to the opposite extreme, and that seems to have fixed the dead spot. I can once again pull away smoothly without stalling now.

So I guess I'll just run with this carb now to see how the two nylon parts fare in use.

Interesting, I have a bit of hesitation on my spare carb, accelerator jet/pump appears to work ok but when it kicks in is of course important, hadn't thought of that... thanks I will check it.

Another plastic bit there I see, maybe it's worn.

If you ever do anymore plastic bits I think captains seat arem rest bolt covers may be in demand

[kevtherev]

Yes very interesting
I too have this hesitation.. Looks like I too will be checking this

[CJH]

Another plastic bit there I see, maybe it's worn.

Nope - not going there. It doesn't look worn on any of the carbs I've got, and besides there's a threaded metal insert that's unlikely to be easy to source.

If you ever do anymore plastic bits I think captains seat arem rest bolt covers may be in demand

I don't have those seats in my van, so I've no idea what that part looks like. Is there something about it that makes it difficult to source some other way?

[CJH]

It seems like that cam adjustment hasn't cured the problem completely after all. Maybe it's masking some other underlying problem now. I took the van out for a run from stone cold this morning. The choke and the fast idle worked ok, although the fast idle wasn't as fast as I remember with the other carb, and it seemed to come off too soon - it was stalling at idle while the temperature gauge was still rising. So choke adjustment needed I think.

Once fully hot, the stalling disappeared, and pull off from a stand still is almost perfect, but not quite. I think something else isn't quite right because there's a general roughness to the idle and a slight roughness/lumpiness when driving, which clears at higher revs. I think I'll have to strip it apart and make sure all the jets are clear and everything's working ok.

With hindsight I should perhaps have tried the new parts on a known good carb - at this point I still can't categorically say that these running problems aren't due to the new parts.

[Mocki]

My bits arrived today, and if it's not to finger numbing cold in the garage I may have a session rebuilding one of my spare carbs now I have all the bits ...... So thanks muchlee for the swift movement from discussion to design to manafacture to delivery on these bits ......

All three of our t25s are lpg , two of them have worn and annoying carb issues , one only manifests it's self on petrol the other is crap on lpg and petrol from cold until it's been running a couple of mins , so hopefully I can cure that one with a carb change once I have rebuild, cleaned returned and repaired one of these carbs
The other one has been off the road three years so no hurry getting round to that one !
Watching this thread for more info ......

[CJH]

Haha - since everyone on this thread seems to have problems, the casual reader could be forgiven for thinking that these carbs are difficult to get running right. There's very little in the way of adjustment though, so provided the basics are right (no air leaks, clear jets, rubber bits and vacuum bits in good order etc) they ought to just work. At least that's what I'm telling myself before I can give this spare of mine another going over. If that doesn't work I reserve the right to change my mind.

[CJH]

I've been flicking through my Haynes carb book, and there are a couple of points relating to this accelerator pump.

The first is that the adjustment is opposite to the way I described earlier. That is, to get the maximum volume of fuel injected by the pump, the pump lever has to move the greatest distance during pumping, so the cam has to be adjusted as far left as possible. Like the image of mine before I adjusted it in fact:



This makes sense - the lever operates a pump, so if the 'pump handle' adjustment has already 'used up' half its travel then the rest of the travel will pump less fuel. In my case, I think it needed to be adjusted a bit to take up the slack, but maybe by moving it all the way to the right I've limited the amount it can pump.

Also, under 'Fault Diagnosis' there's a section on 'Hesitation'. It mentions that the accelerator pump diaphragm uses a spring loaded ball in a slot, behind the lever, and when that spring becomes weak with age there will be a delay in the response of the pump to throttle movement, which can cause a flat spot. I'm pretty sure I replaced the diaphragm (which includes the spring loaded ball) when I did the refurb kit, but it's something else to check.

[itchyfeet]

My carb developed a petrol fault recently, it was so bad it would hardly pull away, it ran fine on LPG.
I first though it was the second throttle not opening because the pipe was off but perhaps I knocked it off.
Changed bypass valve and cleaned up the lower gasket and it was very much better ( indicating air leak from one of those) but still not 100% right.
had it appart and can't see anything wrong, it had a rebuild kit several years ago.

https://club8090.co.uk/forum/viewtopic.p ... y#p8123845" onclick="window.open(this.href);return false;

I swapped to my spare carb which is better again but not 100% eityer on petrol, lpg is fine, so I'm on the same learning curve.

Are you replacing lower gaskets or main gasket when you swap carbs and what, if any, sealant do you use? I wonder if this could be air leaking on the lower gasket or somewhere else.

[CJH]

Are you replacing lower gaskets or main gasket when you swap carbs and what, if any, sealant do you use? I wonder if this could be air leaking on the lower gasket or somewhere else.

I made new gaskets for the spacer about a year ago, from fairly thick gasket paper, but haven't replaced them since then - including when I ran the LT carb for a while, and swapped the carbs over at the rolling road place. I assembled them dry. I agree though, an air leak down there would cause rough running, and that's something I'll check carefully when I take this spare carb apart again, probably at the weekend. I should check one of the reference diagrams - is there supposed to be a gasket either side of the spacer? I had a strange problem in that the tip of the accelerator pump lever binds on the top of the inlet manifold when the cam pushes it all the way down, and this causes the cam to get wedged behind the lever - effectively jamming the throttle open. I'm using a pump lever that's had the tip trimmed off by a previous owner. I think this is partly due to a build up of grease and grime on the top of the inlet manifold, but maybe it's because I'm not using thick enough gasket(s). The spacer is definitely right - I have a few that are all the same thickness.

The main gasket between the two carb halves is new, and also assembled dry.

I was worried about not having the 10mm core plug at the end of the choke spindle (and I've now ordered some), but since the spindle bush is in open air anyway from the underside - the other side of the little plastic linkage I've made - I don't think that core plug is to prevent air leaks. It doesn't seem necessary.

[itchyfeet]

This is my acc pump from my original carb (now off the van) on spare manufold.

You are right lever touches the manufold, well as good as, there may be a papers width gap.

I have three carbs and the spacers are all stuck to the carbs, It never occurred to me that that interface could have failed, maybe I need to remove them and reseal them on both faces.

you are right core plug can't matter

[itchyfeet]

Just had a good look and the origional carb does not appear to have a thin paper gasket between spacer and carb, that doesn't mean it left the factory that way but I suspect it did.

[itchyfeet]

Looking at the second choke I wonder if this opens slightly at idle when vac is high what happens?

On mine there is a small movement, I wonder how much movement there is with the replica part?

[CJH]

I have three carbs and the spacers are all stuck to the carbs, It never occurred to me that that interface could have failed, maybe I need to remove them and reseal them on both faces.

OK, so maybe the gasket goes below the spacer, and the spacer is fixed to the carb with a sealant rather than a gasket. I've looked through all the books and guides I have and none of them show the spacer and gasket(s).

Looking at the second choke I wonder if this opens slightly at idle when vac is high what happens?

On mine there is a small movement, I wonder how much movement there is with the replica part?

Yes, this movement is governed by the geometry between the plastic part and the arms of the u-bracket on the second throttle spindle. I've tried to reproduce this in the replica part. My initial prototype had the geometry slightly wrong so the amount that the flap opened was too much, but I'm confident that the final part that I had printed in numbers is a good match for the original in this respect.

I don't really understand where the vacuum for the second venturi comes from. Will there be enough at idle to open this small gap, or is there only enough vacuum at higher rpm?