Pierburg 2B5 vacuum circuit

[philipayton]

Maybe it’s T’d off that hose?

[GT_II]

Comparing the diagrams for the 2B5 in the VW workshop manual, the Haynes Mk2 Scirocco manual and the Haynes Solex & Pierburg carb manual, the Haynes Scirocco manual is clearly incorrect. The hose labelled E in the Haynes Scirocco manual goes to the thermovalve on the air cleaner (rear connector I think, shown as the thicker end of the valve in the Haynes carb manual). The econometer if present would connect to a port on the brake servo vacuum pipe.

[philipayton]

Thank you once again - will give this all a try. Much appreciated

[philipayton]

Just sorted all that and tested. No noticeable change. However when I bypassed the temperature regulator in the air inlet box it was better. I’m not sure it was getting sufficient vacuum to open the flap before. So either I have a vacuum leak somewhere or the temp regulator is faulty.

It’s not perfect still. Very responsive on the throttle but still jumpy when cruising at low revs. Definitely better though.

Think I need to search for a leak.

[GT_II]

Also, check the condition of the carb mounting flange - a split in the gasket could affect the gas flow

[philipayton]

There is no visible damage to the mounting flange but there is oily residue there suggesting a leak. Maybe would be good idea to get another one to eliminate that.

[philipayton]

Waiting for the carb flange to arrive. Have spotted the rocker cover gasket has had it - leaking at the cam belt end. It was a cork one and the rubber bit over the cam had broken in two. New rubber one on its way.

Is it possible that this could lead to an air leak that would cause my symptoms? Ie starts ok, idles ok, accelerates ok but lumpy when running at constant low revs like when stuck in traffic.

Previous owner tells me it ran ok before so to start with I’m just focusing on things that might deteriorate due to the car standing for a while.

[RussGLAuto]

Hi - I have the same model year / 2B5 carb.

This is the correct carb for the year. Is she a GL by any chance?

Question - does the car have the original filler neck / tank / fuel lines?

Thanks

Russ

[RussGLAuto]

Whatever you do from here, please DO NOT get the Webber upgrade.

I'll help you work through any issues you have to get her back to A1. It may not be cheep, and not for the faint hearted. But have a little faith, and we'll get your car running sweet as like mine is with the original 2B5!!

Cheers

Russ

[philipayton]

Thanks Russ - and yes it’s a GL with the single wiper.

Filler neck has been done but not fuel lines. According to the previous owner it ran fine before the gearbox broke and it was laid up for a while. Fuel filter in engine bay shows clean fuel.

Next job, if after fitting rocker cover gasket it’s still not right, is to remove the jets and blast some air through. If still no good then probably carb off for a refurb.

Given it was ok before I’m hoping that won’t be necessary!

I have no intention of swapping out the carb - at least for now. It idles sweet (although a little high at 1100 - - maybe that’s the vacuum leak?) and accelerates smoothly.

[philipayton]

I’ve fitted a new rocker cover gasket and carb flange. I’ve removed the jets and blasted them and the jet ports with air. I’ve added some fuel system flush and ran about 20 miles. It’s better but still not right.

I think the next job is to remove carb, clean it and refurb. The carb refurb kit came with the car.

Provided I put everything back as it came off is there anything I need to be aware of? I have the Haynes manual but have already established that it’s not quite right - at least for the vacuum circuit.

[RussGLAuto]

Hi Phil,

You say it's still not right, what is she doing exactly? Can I recommend you check the fuel tank for rust particles via the sender port under the rear bench seat. My 82 GL had the filler neck changed, what wasn't done was the tank and hard fuel line from it to the engine bay. It was thick with rust.

That filter may look clean, but if it has even the smallest black specs on it, that's your problem. Change that hard fuel line and ensure the tank is clean.

To start from cold:
Depress the accelerator once and release to prime the carb. (twice if longer than a week since last run).
Start. Engine should fire immediately and rev to c. 2300-2500 RPM and remain there. After 15-20 seconds blip the throttle (with one’s right foot) and the revs will fall to c. 1200-1500 RPM.
Don’t wait for the engine to warm up, drive off. Once warm, she should idle at c. 950 RPM.

To start from warm:
Slowly depress the accelerator and hold full throttle down.
Start and release accelerator while cranking the engine.
As a side note, when I got the car I was filling it with regular E5 - 95 RON unleaded. Having read the owner’s manual, it states to use unleaded fuel of not less than E5 - 97 RON.
Woops! So, she’s now guzzling Super Unleaded.

[philipayton]

Thanks Russ
I will give all of that a try - especially the super unleaded.
I have double checked the timing and moved it very slightly. Will see how it is. And will check the sender port under the seat as you say.
Will feedback!
Thanks again
Philip

[mark1gls]

Any old car now should NOT be using normal unleaded petrol as the ethanol has increased to 10% (E10) and it’s not kind to rubber hoses and old carbs.
You can buy an additive to put in each time you fill up but best to just use Super unleaded as that’s still 5% ethanol (E5)

[RussGLAuto]

Thanks Russ
I will give all of that a try - especially the super unleaded.
I have double checked the timing and moved it very slightly. Will see how it is. And will check the sender port under the seat as you say.
Will feedback!
Thanks again
Philip

No worries Phil, it's a pain in the proverbial to change that fuel line, you'll probably have to enlist a garage to do it if you don't have a lift as I did £££, but that was where the problem was. The pipe looked fine on the outside with no corrosion.

Can get Golf Mk1 fuel lines (same as mk2 Scirocco) from Classicvw.co.uk.

Clean fuel is a must and your best starting point. If you want to bypass the fuel system, you could always hook up a fuel can feed directly to the swirl pot. Check the running of the engine. Please don't drive it like that though!! Oh, that was another item my GL was missing... fuel / air separator or swirl pot.

Normally bolts to front of the engine next to the rocker cover.

Good point made by mark1gls too. Don't use E10 fuel.