Scirocco Register

I have a Mk2 '88 Scala with EX engine and Pierburg 2e2.

Timeline:

• Got the car on the road after sitting for a few years
• Ran happily for about a month
• Started developing intermittant hesitation when pulling away from stopped - every now and then the revs would dip from idle and take a second or two to build back up
• About two days later it did the above pretty much constantly. On my way home it suddenly started lurching and struggling regardless of what gear I put it in, and I had to struggle to get it off the road without stalling.

After that I could get it fired up but it simply did not run right, sitting at about 1k when cold, 500 and falling til it stalled when hot.

Fuel seemed to be getting up to the carb fine - there was the tiniest little air bubble in the top corner of the inline filter, and I had also replaced all the fuel lines and jubilee clips.

On the ignition side of it, I had before getting the car on the road replaced essentially the entire ignition system: spark plugs, ht leads, tci, dizzy rotor, coil.

This led me to believe that the problem lay somewhere with the carb, thinking it might be a gunked up jet or drilling or something similar, so I ordered some bits up and did the following:

• Split apart in order to spray out the jets and all the gunk inside (I collected loads of soot particles and some bigger solid chunks)
• Took the waxstat off and verified it extended with heat properly
• Replaced and readjusted the PDU (it was cheap enough I thought it a better option than getting a guage and what not to test it). Set to 2.5mm when sucking on the vac line, 4.9mm when pushing on the little bolt at the back.
• Cleaned all the shit out of the housing for the autochoke, and put it back on
• New red gaskets with rod + oring end cap thing that is shaped like a rounded parallelogram and sits on the side (can't remember what it is for)
• New gasket for the accelerator pump, made sure it was the same size as the old one
• New gasket between the two halfs of the carb
• New carb flange
• I took the inlet manifold off and the coolant channel grommet was positively shredded, so new grommet and gasket
• Replaced the vacuum lines of the carb with 4mm inner diameter lines.
• Replaced the o'rings on the 3 point and put some thin grease on them.

And some checks carried out:

• Put a compression tester guage on all four cylinders and it had good compression
• 1kohm across each ht lead
• 1kohm across rotor cap
• 0.7ohm from top to bottom of the spark plugs
• Spark plugs are a bit black / wet from fuel
• Solenoids click when the electrics are on
• 12v to both solenoid plugs
• 0.7ohm from carb to battery -ve
• 14.9ohm between autochoke lead and battery -ve
• 12v to manifold hedgehodge
• I had no 12v to the autochoke, but there was 12 going into one side of the sender, and I did have the engine running about half an hour ago, with the choke flap opening it self, so I believe the coolant may be warm enough that it is turned off. I will check next time I am home.
• Waxstat extends properly and retracts with a small amount of pressure

I buttoned everything up, bled the fuel thru, and after a bit of fiddling managed to fire her up.

After a lot of trial and error I found that screwing the mixture screw (the one accessible via the bung on the airbox) fully in, then unscrewing it by two full turns seemed to allow the engine to start without the carb popping and spewing a ton of smoke.

This is what happens when starting it up:

• Goes up to 1.1k and seems to sit there steadily
• Weirdly it doesn't do the 2k blip it used to do
• Can put my foot on the throttle and rev it up happily to 2k
• After a minute from starting I took the air filter out and glanced at the choke flap - it was wide open at this point (having started just about closed).
• I left it for 5 minutes and over that period of time it dropped to about 900 and seemed happy with that. I could still rev it up to 2k happily.
• Throughout all the above it was spewing a blanket of petrol smelling blue tinged smoke over the drive and it sounded really burbly

I tried at first turning the screw in clockwise a quarter turn at a time, leaving it for 10 seconds and then doing another quarter turn. This didn't seem to change the sound or amount of smoke coming out the back, but after 2 full turns the revs had dropped by about 200, I tried throttling it up and it immediately cut out.

I subsequently came back after a few hours to let it sit and go back to "cold"/ambient temps for the purpose of repeatability and tried the same but turning the screw counter clockwise. Effectively the same thing happened.

I also ran the engine up once, messing with nothing, just letting it get hot, and it seemed happy to throttle up, but was stilling spewing smoke everywhere.

While running the fuel filter was chock full of fuel, and after it cut out there was still plenty of fuel in the filter. The mechanical fuel pump and air/vapour seperator/pressure regulator have both been replaced. It used to struggle to start and I had to pump the throttle once or twice depending on how long I had left it without starting it for the couple of months when I got it ready to go back on the road, after replacing the air/vapour seperator it would start happily when turning the key, now I have to give it a pump to get it run, but it may just be that method of bleeding the air doesn't get all the air out (I split the return line, blow air into return to the tank, let the fuel filter all fill up and make sure the flow from the return port of the seperator is laminar when it goes into my catcher bottle).

Effectively I seem to have a mixture that can never be set right it seems.

I'm going to be away for about a week without access to the car. I'll likely take the carb apart and rebuild it, replacing everything and measuring it all up properly i stead of my previous half-assed cleaning of it when I get back on the weekend, but I thought I would make this post to see if anyone might be able to point out a very obvious problem, or potentially point me in the right direction.

I tried to put as much detail in this post as possible, so if you read the whole thing, thanks very much for your time.

Technically you should check the ignition timing before setting the carb. However, that is unlikely to explain the changes you have experienced, unless the distributor body is insecure or the distributor is on its way out.

In setting the idle mixture, I learned early on that the mixture control screw on the 2E2 carb works in the opposite direction to most other carbs. On the 2E2, it turns clockwise to enrich, anticlockwise to weaken. The mixture screw and idle speed screw need to be turned alternately to achieve an idle speed of between 700 and 800 rpm (900 to 1000 rpm for auto transmission). The idle speed screw is the (I think 13mm) hex screw on the back of the 3-point unit, a bit tricky to reach without burning your hand on the exhaust manifold, but accessible with a spanner between the carb and the bulkhead, I think from the opposite side of the carb.

This all assumes your carb basic throttle and warm-up cam settings are correct, and there are no other faults. For completeness, the adjustments should be done with the engine at normal temperature, with all electrical consumers off, all vacuum hoses connected and the crankcase breather hose disconnected from the rocker cover.

From your description, it seems your mixture was way too rich. Finding the optimum mixture is difficult without a CO meter (to achieve between 0.5% and 1.5% CO), but with trial and error, you should be able to achieve at least a reasonable performance. To start with, I would turn the mixture screw within the range which gives you highest idle speed, then adjust the idle speed screw down to achieve the correct idle speed, then repeat. Finally, adjust the idle mixture screw anti-clockwise to the point at which the revs start to fall off, then back maybe a quarter of a turn.

At this point the idle mixture will probably be a bit weaker than ideal, but at least it should easily pass the MOT emissions test (less than 3.5% CO at idle). Ask for an emissions printout when you get it MOT'd, so you can check whether you need to tweak the mixture, though as the crankcase breather hose will be connected during the MOT test, the CO reading will be a bit higher than with the hose disconnected.

double check all vac lines are good and not split
when i eventually gave up on my pierburg and bought a weber when i removed the pierburg right at the very back was a split vac line that was the source of my woes, i dare say if i had of replaced that line the pierburg would work fine but i fitted the webber instead for ease

GT_II wrote: ↑Mon Nov 11, 2024 1:53 am In setting the idle mixture, I learned early on that the mixture control screw on the 2E2 carb works in the opposite direction to most other carbs. On the 2E2, it turns clockwise to enrich, anticlockwise to weaken. The mixture screw and idle speed screw need to be turned alternately to achieve an idle speed of between 700 and 800 rpm (900 to 1000 rpm for auto transmission). The idle speed screw is the (I think 13mm) hex screw on the back of the 3-point unit, a bit tricky to reach without burning your hand on the exhaust manifold, but accessible with a spanner between the carb and the bulkhead, I think from the opposite side of the carb.

This all assumes your carb basic throttle and warm-up cam settings are correct, and there are no other faults. For completeness, the adjustments should be done with the engine at normal temperature, with all electrical consumers off, all vacuum hoses connected and the crankcase breather hose disconnected from the rocker cover.

From your description, it seems your mixture was way too rich. Finding the optimum mixture is difficult without a CO meter (to achieve between 0.5% and 1.5% CO), but with trial and error, you should be able to achieve at least a reasonable performance. To start with, I would turn the mixture screw within the range which gives you highest idle speed, then adjust the idle speed screw down to achieve the correct idle speed, then repeat. Finally, adjust the idle mixture screw anti-clockwise to the point at which the revs start to fall off, then back maybe a quarter of a turn.

Ah I see I'll give it a shot adjusting using both when I have the chance, thanks.

I agree that I think the mixture was way too rich. What baffled me was that after changing the mixture as soon as I put my foot on the throttle it would cut out. Will see if that sorts itself out once it's sat at a better mix.

james butler wrote: ↑Mon Nov 11, 2024 10:25 am double check all vac lines are good and not split
when i eventually gave up on my pierburg and bought a weber when i removed the pierburg right at the very back was a split vac line that was the source of my woes, i dare say if i had of replaced that line the pierburg would work fine but i fitted the webber instead for ease

Yeah some of them looked like they were on the way so I put some new 4mm silicone hoses on. (I've however since read silicone may not be the best for withstanding bay temps).

When I rebuilt a Pierburg 2e2 during lockdown I found the most troublesome part was the 3/4 point unit. I bought several complete carbs to have plenty of parts to choose from and this part failed to hold vacuum on all of them. New units are scarce and very expensive. In the end I did source a secondhand working unit to complete my build.

The symptoms you describe tend to be associated in the documentation with poor flow of coolant affecting the operation of the auto-choke. I know you have replaced the notorious o-ring but it would be worth checking the body of the auto-choke gets too hot to touch after a few minutes running from a cold start.

One of the vacuum hoses to the pulldown unit should have a restriction in it. If you have changed some vacuum lines did you transfer this to the new line? If not, it probably won’t work correctly and will affect the operation of the choke.

Another thing that might cause over-fuelling is if the accelerator pump injection nozzle is faulty. This squirts a measured amount of fuel into the primary port on hard acceleration. The nozzle is supposed to have a ball bearing in it but if it is missing fuel can continue to pour out of the hole left by the missing ball bearing when the accelerator is operated.

What worked for me was stripping the carb into literally all its component parts, putting them through an ultrasonic cleaner and then reassembling whilst making and checking all the necessary adjustments. The most useful sources of information for me were the 2e2 service instruction PDF in English, the Haynes Solex and Pierburg manual, SkyRocket Automotive’s YouTube channel and also James Akers’ videos on disassembling and reassembling a VW T25 / T3 2e3 carb which is very similar to the 2e2.

Good luck with your project. In my opinion the Pierburg, when working correctly, is far superior to a Weber.

WreckTangle wrote: ↑Wed Nov 13, 2024 11:17 pm When I rebuilt a Pierburg 2e2 during lockdown I found the most troublesome part was the 3/4 point unit. I bought several complete carbs to have plenty of parts to choose from and this part failed to hold vacuum on all of them. New units are scarce and very expensive. In the end I did source a secondhand working unit to complete my build.

The symptoms you describe tend to be associated in the documentation with poor flow of coolant affecting the operation of the auto-choke. I know you have replaced the notorious o-ring but it would be worth checking the body of the auto-choke gets too hot to touch after a few minutes running from a cold start.

One of the vacuum hoses to the pulldown unit should have a restriction in it. If you have changed some vacuum lines did you transfer this to the new line? If not, it probably won’t work correctly and will affect the operation of the choke.

It was missing from the original hoses so I don't have one at the minute.

Another thing that might cause over-fuelling is if the accelerator pump injection nozzle is faulty. This squirts a measured amount of fuel into the primary port on hard acceleration. The nozzle is supposed to have a ball bearing in it but if it is missing fuel can continue to pour out of the hole left by the missing ball bearing when the accelerator is operated.

That makes a lot of sense. I will definitely have a look at that if adjusting like GTII said doesn't help.

What worked for me was stripping the carb into literally all its component parts, putting them through an ultrasonic cleaner and then reassembling whilst making and checking all the necessary adjustments. The most useful sources of information for me were the 2e2 service instruction PDF in English, the Haynes Solex and Pierburg manual, SkyRocket Automotive’s YouTube channel and also James Akers’ videos on disassembling and reassembling a VW T25 / T3 2e3 carb which is very similar to the 2e2.

Good luck with your project. In my opinion the Pierburg, when working correctly, is far superior to a Weber.

Do you happen to have a copy of that PDF that you could share? Would be very handy :)

If you search "2e2 manual" on Google, you will find it