Hopefully someone on here has seen this before, i'm running an MH engine with the Pierburg 2E3 on my Derby which has run perfectly up until yesterday.

It won't idle and it's misfiring on reving up from around 1500 rpm, it can hold it's revs using the throttle but if you release the pedal, it dies.

So far i've stripped and cleaned the cab to within an inch of it's life

Replaced Carb mount

Have new Dizzy on the way (was thinking maybe hall sender?)

Verified that it's not fuel pump related

Timing is spot on

Plugs are clean and gapped

Idle cutoff valve verified working (although this has no effect on the running of the car at all)

Does something block on these carbs causing this poor running.

The car will drive fine under heavy throttle, but will instantly die if you lift off.

I'd be delighted to hear from anyone who has fixed a 2E3!

Also, the carb has very low mileage >40K and the choke unit is new.

Edited 13 June, 200917 yr by euro-derby

Once had this on my 1.8 scirocco's pierburg a hell of alot of carb cleaner seemed to help.

I'm puzzled with this, you can eat your dinner of the carb, it's spotless inside and out. I've blown all of the jets out, but to be honest they were already clean.

Maybe i'm overlooking something else. Going to try a brand new carb mount and a new distributor next week. Fingers crossed. Any other suggestions would be appreciated.

You say the idle jet is clear and the carb is clean and your are sure plugs, rotor, distributor cap hall sender etc are ok.

It'll probably be a piece of rubber perishing.

Check all the vacuum tubes.

On mine the choke pulldown unit diaphragm was split.

Check the choke flap gap and that it opens more when the engine fires and is open fully when engine warm

Later the internal heater for the autochoke failed.

Then the accelerator pump diaphragm.

One time I forgot to reconnect the earth contact wire firmly.

Oh Pierberg joy.

Pretty much everything he just said. If that doesn't work, give your idle screw a spin, remember how many turns you did which way though so you can put it back. From what you're saying though, sounds like a problem with the first choke.

Is your coolant topped up and bled?

Thanks for the replies, plugs are good and clean. Both pulldown units are working (although I believe that they are not used for idling).

It's very weird, the car ran to club charlys and back faultlessly (500 miles!), left it in the garage for two days and then wouldn't run properly!

It began idling at about 200 rpm and now it won't idle at all. I'm thinking something is blocked still or I have a massive vacuum leak. I've checked all vacuum connections, the vac advance on the distributor is okay, the small orange device in the air cleaner housing is closing the warm air flap on the intake correctly. Can't be much left!

@Yeti - The coolant is topped up to the max, not had any cooling system problems - not leaking anywhere.

Edited 14 June, 200917 yr by euro-derby

When I had the pierburg I never got to the bottom of this other than thinking it was something to do with how the automatic choke engages. At the time i thought it was a wax stat type but it's not. I reckon it something to do with how the coil in the automatic choke unit engages to move the butterfly for idle...

I have a vague recollection of a thread where there was some sort of adjustment of the linkage between these but had already gone onto the weber DTMR carb which eliminates this problem with it's manual choke.

The pierburg comes in for a lot of stick I reckon because it is complex but as far as I know when running well are actually very efficient carbs.

I'm sure someone on here will know?

It began idling at about 200 rpm and now it won't idle at all. I'm thinking something is blocked still or I have a massive vacuum leak. I've checked all vacuum connections, the vac advance on the distributor is okay, the small orange device in the air cleaner housing is closing the warm air flap on the intake correctly. Can't be much left!

Sounding more like airleak. Shaving foam is good diagnostic tool. It bubbles where the air is entering.

When it can't hold idle does it splutter or does it die gently?

If the latter you might have rusty sludge in the feed or return lines from the fuel tank so not enough fuel is getting into the carb wells.

Float level of petrol is low, very lean mixture, slow idle.

The 2E3's plastic swirl pot reservoir masks this impede line problem as it acts as local reservoir.

Up the revs, there's lots of suction from the mechanical pump fuel gets through engine runs about equal rate to consumption.

How clean is the inline fuel filter?

How well does the pump flow on the starter motor?

Thanks again for the advice guys. I'm slowly narrowing this down.

So far i've found:-

Rubber seal for the idle cutoff valve split (causing air leak maybe)

Carb top gasket split in to two pieces (new one on order)

Definately suspicious of an air leak, going to check the rubber O ring on the Hedgehog heater, as if that's split it'll draw air in like a bastard.

No rusty sludge in fuel lines, pump delivers well. In fact when it cuts out, I can remove the top of the carb and it's full of fuel. I've got a new swirl pot on there (steel one fitted about 6 months ago).

The engine will rev lovely but you need to keep varying the pressure on the throttle. If you hold your foot still it dies, need to keep pumping the pedal. As soon as you lift off, it dies so quickly, like it's run out of fuel. Instantly restarts though with throttle!

Cheers, so far.

Also don't ignore the repairative powers of revving the tits off it briefly. Done this on so many mk2's that have been acting a bit ginger beer and it often works.

The engine will rev lovely but you need to keep varying the pressure on the throttle. If you hold your foot still it dies, need to keep pumping the pedal. As soon as you lift off, it dies so quickly, like it's run out of fuel. Instantly restarts though with throttle!

Good news about the pipes and pump.

That's only a small airleak though (bar the hedgehog).

Sounds like you are starting and running using the accelerator pump jet by pumping the gaspedal or on 2n'd stage jets.

Instant cut off, eh? Is the idle cutoff valve actually moving it's stopper plunger when 12 v applied ?

Earth contact good ?

I assume the valve only cuts the idle circuit in primary stage.

The engine will rev lovely but you need to keep varying the pressure on the throttle. If you hold your foot still it dies, need to keep pumping the pedal. As soon as you lift off, it dies so quickly, like it's run out of fuel. Instantly restarts though with throttle!

Good news about the pipes and pump.

That's only a small airleak though (bar the hedgehog).

Sounds like you are starting and running using the accelerator pump jet by pumping the gaspedal or on 2n'd stage jets.

Instant cut off, eh? Is the idle cutoff valve actually moving it's stopper plunger when 12 v applied ?

Earth contact good ?

I assume the valve only cuts the idle circuit in primary stage.

I think you are definately right about running on the accelerator pump. My idle fuel circuit is definately clear now and the new carb gasket kit came today so i'll fit that tomorrow night. That idle cutoff is moving the plunger when 12v is applied, making the a good click every time. It appears to block the idle fuel circuit when not energised.

Carb itself seems to have no wear on it, I was expecting the butterflies to have play in, but they seem just fine. Thanks for all your help so far (and Yeti of course), i'll get the thing assembled again to see what state it's in tomorrow.

I've got a spare carb shoud you need it.

Right then, firstly it's fixed!

Secondly, i'm unsure what exactly the problem was. Did a gasket kit change, new carb mount and an epic cleanup and it runs beautifully! suspecting a massive leak at the carb base but unsure.

Thanks for the advice lads, much appreciated!

Great stuff and respect for sticking with the pierburg.

That's great. Well done for persisting.

I reckon that the split top gasket meant there was insufficient pressure differential from the float bowl (atmospheric)

to the jet wells (under suction from inlet strokes of pistons) to get sufficient mixture through the idle circuit.

Pushing the gas pedal would squeeze the accelerator pump diaphragm to spray small amounts of petrol in.

Where'd you go for the service kit ?

That's great. Well done for persisting.

I reckon that the split top gasket meant there was insufficient pressure differential from the float bowl (atmospheric)

to the jet wells (under suction from inlet strokes of pistons) to get sufficient mixture through the idle circuit.

Pushing the gas pedal would squeeze the accelerator pump diaphragm to spray small amounts of petrol in.

Where'd you go for the service kit ?

Certainly sounds feasible, i think it was a combination of little faults that broke it!

I bought the service kit from Dellorto, the kit's very comprehensive it even contains a new needle valve.

Dellorto....

Cheers

I threw away two Pierburgs which were in perfect working order. I couldn't bring myself to give them to anyone because it was only a matter of time before they became unreliable,and they're not very efficient at the best of times.

I figure they were better used for making beer cans.

I threw away two Pierburgs which were in perfect working order. I couldn't bring myself to give them to anyone because it was only a matter of time before they became unreliable,and they're not very efficient at the best of times.

I figure they were better used for making beer cans.

Shame to bin them - I would have taken them off your hands! Mine's been running fine for a few thousand miles since this problem, but time will tell.

These carbs are actually quite reliable if you are car is looked after. Blocked breathers and oil leaks and fiddling with carb settings lead u up the garden path. Lost count of the number of Polo's I've owned and i can honestly say the only one that I had to spend few hours on because of carb prob was one I have right now. That was down to my father driving it for a whole year tho, not doing simple things oil changes, plugs, air filter oil filter etc etc etc. The engine mounts starting to need replaced makes the engine wobble a bit more than it should which starts loosening carb gaskets and shaking things too much that shouldnt be shaken lol. Shakey engine ( or gearstick )when idling normally usually indicates engine mounts needing replaced. Watch out for that one since u already spent time on the carb and its running schweet now. Glad you are revving up n down the gears as normal now bud.

I threw away two Pierburgs which were in perfect working order. I couldn't bring myself to give them to anyone because it was only a matter of time before they became unreliable,and they're not very efficient at the best of times.

I figure they were better used for making beer cans.

Shame to bin them - I would have taken them off your hands! Mine's been running fine for a few thousand miles since this problem, but time will tell.

These carbs are actually quite reliable if you are car is looked after. Blocked breathers and oil leaks and fiddling with carb settings lead u up the garden path. Lost count of the number of Polo's I've owned and i can honestly say the only one that I had to spend few hours on because of carb prob was one I have right now. That was down to my father driving it for a whole year tho, not doing simple things oil changes, plugs, air filter oil filter etc etc etc. The engine mounts starting to need replaced makes the engine wobble a bit more than it should which starts loosening carb gaskets and shaking things too much that shouldnt be shaken lol. Shakey engine ( or gearstick )when idling normally usually indicates engine mounts needing replaced. Watch out for that one since u already spent time on the carb and its running schweet now. Glad you are revving up n down the gears as normal now bud.

Great advice, thanks for that. You are right about engine mounts, mine are probably past their best at 30 years then! Luckily the engine on mine is rarely thrashed (no point ragging the heart out of the old thing) and is very low mileage.

I'm definately taking your advice on engine mount rubbers.

Thanks again for the advice guys. I'm slowly narrowing this down.

So far i've found:-

..........

No rusty sludge in fuel lines, pump delivers well. In fact when it cuts out, I can remove the top of the carb and it's full of fuel. I've got a new swirl pot on there (steel one fitted about 6 months ago).

............................................

Cheers, so far.

Hi Vic

I assume that you are referring to the evaporation chamber as the swirl pot.

May I please ask where did you manage to get hold of a steel one ?

Cheers

Thanks again for the advice guys. I'm slowly narrowing this down.

So far i've found:-

..........

No rusty sludge in fuel lines, pump delivers well. In fact when it cuts out, I can remove the top of the carb and it's full of fuel. I've got a new swirl pot on there (steel one fitted about 6 months ago).

............................................

Cheers, so far.

Hi Vic

I assume that you are referring to the evaporation chamber as the swirl pot.

May I please ask where did you manage to get hold of a steel one ?

Cheers

Hi, the steel swirl pot came from the The Carburettor Hospital

It fits the Pierburg perfectly on the original bracket.

Cheers.