Hi all, I have a strange problem: I can't get any fuel through the carb on a 1985 polo c formel e 1.3. I changed fuel pump and separator, the separator fills up but no fuel gets through to the engine. The car used to run well but sat for years. When starting, the engine kept running on leaner and leaner mixture and cutting out when I pressed the accelerator but revved up well if it got to higher revs. The engine strarts well if I pour some fuel directly into the carb but soon cuts out as the fuel is used up. Is the next step carb strip and rebuild, any suggestions?

The idle circuit is blocked probably.

you need to screw in the mixture screw counting turns gently until it hits bottom. then unscrew it. Insert a rubber tube and blow down it with compressed air/bike pump/keyboard cleaner spray can air.

it should bubble fuel in the carb well.

refit mixture screw (might need a new O-ring).

screw until reaches bottom Gently.

unscrew same turns you counted.

 

or the autochoke is seized. WD40 will let the flap move again.

 

Or the base gasket has bad vacuum leak from drying out.

think it is a 2e3 Pierburg

052129016B

https://www.ruddies-berlin.de/2e3vwdat.htm

there's a filter strainer at fuel pipe inlet. Check that.

Part 2 https://www.catcar.info/audivw/?lang=en&l=c3RzPT17IjEwIjoiQnJhbmQiLCIyMCI6IlZXIiwiNDAiOiJQb2xvXC9EZXJieVwvVmVudG8tSU5EIEV1cm9wZSIsIjUwIjoiMTk4OSIsIjYwIjoiRW5naW5lIiwiNzAiOiIxMjEwIn18fHN0PT03MHx8YnJhbmQ9PXZ3fHxtYXJrZXQ9PVJEV3x8bWRsPT1QTyAgIHx8RXBpcz09OXx8RWluc2F0ej09MTk4OXx8TWFpbkdyb3VwPT0xfHxCaWxkdGFmZWw9PTEyMTB8fEdyYWZpaz09MDAxMjEwMDA5

And part 41 is a swirl pot. that might have crud in if got past online filter.

Edited 4 September, 20241 yr by dvderlm

Many thanks for the advice! I am desperate to try anything that does not require dismantling the carb, although I already bought the set of gaskets. Thanks for the tip with the idle, this sounds very plausible! The engine went slowly, it's been lacking power for some time, now it pretty much refuses to start. Anyway, now I've got my weekend sorted by the sound of it!

And, thanks for the schematic, this is most helpful!

Lacking power, even at higher revs?

The mechanical fuel pump needs to deliver about 3psi at idle.

You can't measure that as you can't idle.

But you should see big spurts if someone cranks and you aim fuelpipe into a bucket.

(No naked flames or smoking)

 

 

I forgot. Pierburg carb needs good earth wire from carb to engine and 12v supply.

Because it has a part channel heater for idle circuit (releases the more volatile fuel molecules) and usually have a fuel cutoff valve to prevent dieseling run on when turn off key.

Cutoff valve might be stuck closed and need 12v.

perhaps you can hear it click if run a wire from battery positive and touch to its spade connector?

 

 

Weber carbs have none of that electrical complexity usually. 

 

Good power needs good spark plugs and plug wires and rotor arm too.

 

 

 

Edited 6 September, 20241 yr by dvderlm
Clarity

12 hours ago, dvderlm said:

..carb needs good earth wire from carb to engine and 12v supply.

Because it has a part channel heater for idle circuit (releases the more volatile fuel molecules) and usually have a fuel cutoff valve

 

cutoff valve is part 28 in exploded diagram.

Channel heater element is part 40.

Edited 6 September, 20241 yr by dvderlm

Aha! Bad electrics make soooo much sense! The thing is, the car's been sitting and not driven, which wouldn't explain clogging of nozzles. Now it won't start at all. But, a dodgy wire would definitely do it! Light in the tunnel :-)

An update - half a can of carb cleaner and the donkey lives!! It's amazing watching the grime wash away into the air intakes... Now it will need some driving to warm the engine through.

 

Thanks for your help and encouragement dvderlm!

Hooray!

The carb jets are tiny so can block easily, especially the idle/slow running jet.

 

Completely evaporated fuel can leave a varnish on carb passages.

E5 and E10 petrol absorbs moisture, and this separates with water at the bottom, which can react with the carb alloy leaving a white crusty powder.

When refilled this can float then block.

 

I used Starbrite Startron Ethanol additive when my Polo was on the road. It's doubled in price.

 

Look up RAC patrolman trick on here for a way to clear the jets without carb cleaner if it gives poor slow running again.

This makes much sense. I don't drive the polo, so it does sound like fuel deposit after evaporation. I used mannol cleaner, which is mostly toluene, dichloromethane and propane-2-ol. Will look up the RAC guide, I was planning on running something in the fuel (ideally without dissolving the fuel lines) to clean the jets. Thanks for the ethanol tip!

Update:

I've changed the fuel pump

I've changed the sedimentation filter

I've rebuilt the carb: a very useful link for pierburg 2e3 at https://vwt25.blog/2016/09/15/pierburg-2e3-rebuild-and-adjustments/

After rebuild, the engine started well and died. The carb sucked all the fuel from the sedimentation filter and the engine won't start, unsurprisingly.

The plan: Will unplug the fuel inlet before the pump and dip in a bottle of fuel, start the car. If this works, will start chasing the lines to the tank.

Edited 2 May May 2 by squirrel

Replace the lines with SAE J30R9 spec which is ethanol resistant.

I think 5.6mm internal diameter is standard.

I used 7.9mm internal diameter metal braided (car is lowered) from tank and some nylon braided PTFE lined for the last meter, but I was upgrading to twin carbs. I only changed the feed line. The return line was clear; when I blew air down it the fuel tank bubbled.

Thank you, this is very helpful! I was looking for the size.

So, checking the vacuum - the pulldown unit is shot. There should be a restrictor in the hose to it, which, I suspect, protects the vacuum in the entire system from unit failure.

Just oredered a new pulldown unit, will update when it arrives.

Good info in the linked T25 info on Pierburg 2e3.

Yeah, a snubber in the tube helps stops a weak or perished diaphragm from splitting.

I have a vacuum gauge plumb in via a snubber. It also smooths out the pulses at low revs.

I wound some tape around a 2.5mm twist drill to set the choke flap gap Starterklappenspalt

(also the loose end of tape can stop the drill bit falling into the carb )

2.5 +-0.1 on my 55kW engine with its stupidly high fast idle.

2.4 +- 0.15 on most polos

This is very useful, thanks! I saw this done in the linked video exactly as you describe. The gap looks fine on mine, the engine idle is terrible and coughs and cuts out as soon as you let your foot off the accelerator. I am still waiting for vacuum pulldown to arrive and hope this will fix the problem. I still think it's useful to add the bead in the vacuum hose, will try to make something out of polyethylene rod with a tiny pinhole.

There was a suggestion of using a thick spacer below the carb and mount for vans and 1.8, 1.9 engines. I don't think it's needed for the 1.3. I think it is important for the longer accelerator plunger.

Edited 4 May May 4 by squirrel

So you can't get it to idle enough reach operating temperature...

is the base mount sealing against the bottom of the carb?

Can you rock the carb with your hands.

If so I would suggest a new carb mount.

A vacuum leak here is bad.

(You might get some short term fix with a blue hylomar gasket sealant).

There are some poor ones out there, sadly.

So a good brand like Febi is worth the money.

I had a Bakelite spacer to keep engine heat away from the fuel in a Weber carb, and a bit longer inlet tract for more low-down torque with a larger carb.

Think it was for an X1/9 and needed surgery for my Weber throttle lever.

Thanks for the suggestions! I think after the heatwave I'll take the carb out, again, and may replace the mount. I was unable to remove the main nozzle during the last rebuild, may give it another try. A spacer came with the rebuild kit but I haven't braved adding it. I guess if the mount's bad, the spacer won't solve the problem. I need to check the throughput of the accelerator pump, as well as the fuel pump. It's turned into a bit of a saga this one...

I'm trying to remember if the Formel E's used an electically-controlled stop valve on the carb as part of the Stop-Start Assist?

It would stop it dieseling on. An idle cutoff valve will have a supply wire to it and an earth connection to a spade on an inlet manifold bolt.

Thanks guys! The Formel E seems to have the low end of the high end components. It does have the electric cut-off valve. I tried it, it clicks nicely. Thanks for the diagramme dvderlm! Unfortunately, I can pretty much recite it with my eyes closed by now but this is the right one, indeed! Very helpful assignment of the two vaccum connectors on the side - explosion A. I found a description bun noone explained which one was which :-)

I am about to replace the carb mount. I bought one but I have the niggling feeling it's not the right one. Just ordered another one from heritage parts. Once it arrives, I'll take the carb all apart. Again... Need to check the throughput of the accelerator pump, as well. Split base fits the bill, will see. I only just realised what split meant - it splits horizontally between the upper and lower plates; I was looking for vertical cracks. TBC

It needs engine vacuum to suck the fuel out of carb through the idle circuit. So base mount being air tight is vital. And top gasket. And vacuum pipes.

And carb needs some flex to stop fuel frothing from engine vibrations.

Don't tighten too much or you can split the rubber around the screw inserts. Hand tight.

Carb needs free passage of fuel from pump, swirl pot and needle valve to enter the well where the float is.

Float needs to be correct height so top of fuel versus holes in emulsion tubes gives correct mixture.

Idle mixture screw fine tunes fuel.

Idle speed screw controls throttle closing gap for air.