STOP PRESS

Have you got an idle cutoff valve solenoid on this new DMTL ?

Cylindrical with a blade connector ?

If so it needs 12volt when ignition live or no mixture will get down the idle circuit.

You must be running with whatever bleeds past the throttle plate.

No, there is no cut off solenoid. Wish there was now. :(

swapping primary and secondary idle (45 for 70, secondary should come in later?),

Sure, secondary stage will be probably be horrible, but it's a simple test that the idle jet size is the problem.

There's a small idle air bleed near the jet and the jet iself and the mixture screw.

If there's no air leak and float level has fuel in the well at right level there's nothing else involved.

if its the proper polo carb kit...i cant imagine youd need to change jets /bits to make it run okay

it should run pretty decent ...maybe swapping bits could make it even nicer but you shouldnt have to mod a new carb

Yeah swapping the jets pushed the flat spot further up the throttle so it does help.

if its the proper polo carb kit...i cant imagine youd need to change jets /bits to make it run okay

it should run pretty decent ...maybe swapping bits could make it even nicer but you shouldnt have to mod a new carb

And this is why I'm worried about this even now, because I'm wondering if all of this is covering up some other problem with the car. The kit said that the jet set up was designed for a DMTR carb and that it might need some tweaking with the DMTL, but it's really not right out of the box at all, we're not talking about it being down on power or drinking too much fuel, it's actually revving up then stalling out completely if you try to drive it normally.

But, there's no air leak, the ignition seems to be working fine, engine block is fine, only other mechanical problems it's got are a couple of oil leaks from the fuel pump and oil breather system and an ageing gearbox. Only thing I can't really test is the vacuum advance on the distributor, but that wouldn't cause this problem even if it were faulty.

Also the fact that I can turn the idle mixture screw right the way out without it impacting the engine is odd, I can't find anything about that online at all.

I really appreciate the help, hopefully I can just get a larger idle jet tomorrow and make it drivable. I've also emailed fastroadcars about this to see if they can shed any light on it.

Edited 1 November, 200916 yr by anessen

id guess theres either a fault with the new carb ...or theres a problem how its fitted

is there no one local that could have a quick look over it for you ?

maybe some decent pics with the aircleaner off ...we might spot a problem

Edited 1 November, 200916 yr by steveo3002

I don't even know where to start looking for someone to look at it. All of the places around here are MOT, Tyre and Exhaust centres. Best they do is play with the idle mixture and idle stop then say "theres a problem with your carburettor mate". Tried searching the great wide internets for "Weber specialists" or "carburettor specialists" but I get nothing around here.

Anything in Wiltshire/Bath/Bristol would work.

I'll get some pictures on tomorrow, but I don't think there's anything obviously wrong with it.

i meant a local forum member ...might take a quick look for you ?

So, it's not idle circuit blockage and the idle might be too small.

On the other hand it still has a flat spot, but at higher revs.

Can't tell if this is the small 2ns stage idle now.

Another idea! DMTL sometimes have only inlet not inlet and return. Are you using a vapour separator/swirl pot to give the fuel that can't

get in because of float needle valve closed ahs a chance to get back to the tank?

There's a plastic one on the Pierburg 2e3.

If not, might the pressue at higher revs from mechanical pump be too much to get atomisation from the primary emulsion tube?

Also the fact that I can turn the idle mixture screw right the way out without it impacting the engine is odd

That says airleak after the throttle plate to me.

So much air getting in that the mixture screw needs to be nearly fully open to achieve tickover.

After that you can't add more petrol to make any difference. Mixture should 1.5 to 2 turns out from bottom.

It's not the carb rubber mount, so what else.

The leak is unlikely to be at the inlet manifold gasket as that would surely only affect one or two cylinders.

Or did you remove the inlet manifold and not fit a new gasket when refitting?

Maybe it's come loose?

The carburettor kit came with a T piece which the fuel line from the pump connects to. One of the pieces has a restrictor thingymabob on it that connects to the fuel return, and the non-restricted piece goes into the carb.

The car ticks over nicely about 1.5 turns out on the mixture screw, but I can unwind it right the way out and the revs stay just the same. According to the bloke at the garage that shouldn't happen.

I never touched in inlet manifold, all I did was unbolt the rubber block with the Pierburg still attached then put it back on ready for the Weber. It's nice and tight, and it doesn't look like it's perished or anything.

What I'll do is try a larger primary idle jet. If that doesn't work, I'll borrow a digital camcorder and put some videos up of what's going wrong. My digital camera died so unfortunately I can't get any photos of anything.

The carburettor kit came with a T piece which the fuel line from the pump connects to. One of the pieces has a restrictor thingymabob on it that connects to the fuel return, and the non-restricted piece goes into the carb.

Throw it away its useless. The mechanical pump pulses fuel in unlike an electric pump and these silly little t-pieces with a restrictor do not work effectively. Fit a swirl pot as its smooths out the flow from one fuel pulse to another and it stops the fuel pressure jumping about all over the place.

Hurrah,

I recommend

GSF car parts.

Part number

12141B

FUEL VAPOUR SEPARATOR Golf mk2 1.6 / 1.8 8/83 >10/91 £24.30

Is there any reason the one from my old Pierburg wouldn't work? £25 expensive to me at the moment.

I put the swirl pot from the Pierburg on, made no difference. I tried two difference sized primary idle jets, 50 and 55, that did nothing.

The flat spot only exists when the choke is open.

And the fucking T piece broke apart when I was removing it from the fuel line and I cut my hand on it. I'm not having a good day.

Sod it, I'm going to buy a new rubber mounting block, do I need to put any sealer on it or put sealer on the bolts or anything?

I suspect it is something simple, any lack of seal round the mounting block/adaptor/gasket will cause problems. I've never changed my rubber block and it is more like a solid piece of plastic. I put plenty of blue hylomar liquid gasket on the old paper (on both sides) of the block and it's been fine. the inlet side of the adaptor plate had a cornflakes packet gasket which worked fine but I changed that to gasket paper with a bit of hylomar.

Are the jets clean? like no chance of anything getting into the holes. The slightest bit of debri would cause mine havoc when I was running an insufficient bolt on air filter.

Are the lean/rich and idle adjustments right along with the adjustment of the hammer of the choke which gives slight revs on cold start?

Is the fuel able to go in and return properly with the swirl pot? my DMTR doesn't need a swirl point because it has a built in return.

Finally ignore my advice if you feel it doesn't apply to your carb lol. this thread might help (see my links) along with the two guides that cover pretty much everything...

http://www.clubpolo.co.uk/forum/index.php?showtopic=145786

Edited 7 November, 200916 yr by MacColl

I sealed up the base of the carb with some gasket sealant and it didn't make any difference, sealed from carb to gasket to adaptor to block to inlet. The jets are all new and clean, the mixture screw is correct as far as I can tell (it will turn all the way out without changing the revs though). The swirl pot seems to be working properly, at least its no worse than the T connector. The carb does not have a built in return.

I called the dealer up today, he's as confused as me. He said I've tried everything he can think of, and that it's very odd that even a slight amount of choke seems to remove the flat spot. On Monday he's going to call up Weber and ask them for advice, but it's possible that the carb itself is faulty somehow. He also gave me the number of a place called Burlen Fuel Systems in Salisbury, they do work on carburettors so I could try taking it down there. One thing he did say was that the valve timing might be slightly out but this is very unlikely but it caused a similar problem on Ford Pinto engines.

But yeah this is really really mystifying (and annoying, and expensive...).

Edited 7 November, 200916 yr by anessen

But yeah this is really really mystifying (and annoying, and expensive...).

Very sorry to hear that.

My uncle used to say "There's nothing wrong with that car that money won't fix."

I'll be delighted to hear what Burlen find.

I think the Pinto valve timing problem is 'charge rejection' where the inlet valve closing time is late the mixture is pushed back out into the distributing inlet manifold by the rising piston and less fuel gets in than otherwise would. Noticeable with a wild race spec cam. Shouldn't happen with a standard head. Cure on the Pinto is smaller venturis.

In finding that I also came across two other Passini gems:

1 "Faulty ignition, too can give all the symptoms of bad carburation. Plugs that appeared adequate before fitting the progressive carburettor may lie down and die when presented with the increased pressures created by improved cylinder filling and higher power output and so can coils and inadequately serviced distributors. Time and time again it happens that the car goes well on the first stage of the carburettor but hardly responds to the second being opened. Sometimes it even slows up as the second venturi being opened. It can of course result from the mixture being wrong on the second stage but often the coil that was adequate before just cannot quite rise to the demands now being made of it." - but you've got electronic ignition...

2 "A faulty water thermostat can affect low speed running... At full bore the effect of the coolant being at too low a temperature is marginal after a few seconds...at light load... the overcooled combustion chamber and inlet port will give symptoms that can easily make one suspect the carburettor. Slight richening will sometmes effect a cure, but it is not a true cure and fuel consumption will suffer even if the plugs don't get dirty enough to cause trouble."

Oh yeah, the Golf mk2 swirl pot is metal, while the plastic Pierburg pot is alleged to crack and cause engine fire. My Pierburg one was still fine when I removed it after 20 years.

Edited 9 November, 200916 yr by dvderlm

My Pierburg pot is made of metal, it was screwed onto the side of the 2E3 (or maybe thats not what you meant).

I suppose it could be the thermostat, but the engine is running hotter than when it had the old carb. It had quite a bad oil leak from the breather system on the back of the engine and some of it got on the exhaust, when it got hot it would smoke from under the bonnet (lots of fun in inner city queues). It did this a lot more with the Weber than the Pierburg. The leak's been fixed now though. Something else to look at tomorrow.

The man from fastroadcars says everything implies an air leak somewhere, because even a slight choke seems to help it along.

just a thought...I've seen people mention that the studs in the adaptor plate will go right through , and if they do that makes it impossible to seal against the manifold

i dont for a minute think its the thermostat , the engine should still run fine anyway

if it was me id remove the whole kit , take it indoors and have a proper good look over all of it ...like i said already take some good close up pics and maybe we can see whats up

The man from fastroadcars says everything implies an air leak somewhere, because even a slight choke seems to help it along.

Yeah, I'm not entirely sure about the water thermostat either. People run twin 40s and bike carbs with no heating, but I suppose the pipework is very short and not distributing.

I also read some other Passini clue about a Mini 875cc with manifold heating "no more than a gesture" suffering from "mid-speed gasp", while a properly heated manifold let a 24/25 (DCD?) be fitted for better top-end and economy.

Can't find that now...

Air leak:

What about the seal for the hedgehog preheater at bottom of manifold ?

I think mine's a circle of nylon or ptfe, but a rubber one could conceivably perish.

Could that be cause of apparent Pierburg 2E3 death?

Your Pierburg swirl pot is a different better material than mine (metal vs plastic), so what chance this seal is worse?

On the advice of the man from FastRoadCars I tried putting in 115/120 main jets. This has helped A LOT, the car is now drivable but it still misfires slightly around 2,000 RPM (most obvious when cruising at 30mph in third gear). So a richer primary has helped it along.

I phoned up Burlen but they couldn't do anything to help me because they just sell parts apparently. They gave me the number of a place next door called Janspeed, and the bloke there told me to try checking the plugs and do a compression test just to rule that out.

The plugs are blackened but not damaged. What with all the different crap that's been going on with this engine for the last few weeks I can't tell if that's indicative of anything at all really, but at least they aren't burnt up or anything. The cylinder compression test came up with 8.5/9/9/8.8 bar which is acceptable according to Haynes (7 bar minimum).

I suppose it could be the heating element, I can't get round there with my EasyStart very well to test it. If I take the intake off would I need to buy a new gasket for it?

I took the carburettor off the car to have a good look at it, no obvious damage or blockages. I would take pictures by my camera's packed up. I'll have to borrow one.

Edited 11 November, 200916 yr by anessen

without being arsed to read most of this, if you need the stupid rubber block thing, I've got one sitting here off a car which idled perfectly. . .

from a pierburg 2e3 carb right? how much?

it'll fit in a jiffy, just pm me your address.