Pierburg 2B5 vacuum circuit

[philipayton]

I’ve just got hold of an 83 1.6 with an 2B5 carb. It starts and runs ok but a bit lumpy at low revs and idle a bit high (1000 rpm). Before getting into the carb I thought I would check the vacuum circuit.

It’s very different to that in the Haynes manual. Is there an alternative vacuum circuit for this carb?

Thanks

[mark1gls]

Not 100% sure what carbs came with the Mk2 Scirocco but shouldn’t it be a Pierburg 2e2 carb ?

https://forum.sciroccoregister.co.uk/vi ... hp?t=11151

[mark1gls]

Idle speed in range, books says 950 +/- 50

What colour are the spark plugs to check the mixture?

[philipayton]

Will check plugs tomorrow - they’re new and only have about 10 miles on them though. So idle probably not much higher than it should be.

I think most 1.6’s did come with 2E2 but the earlier FR engine had the 2B5.

I’m tempted to try rerouting the vacuum circuit per the manual to see how it runs.

[GT_II]

I have the German language VW workshop manual for Scirocco Carbs (1991 edition). This shows only one vacuum hose configuration for the 2B5, so the layout in the Haynes manual should be correct.

[philipayton]

Thanks for that. I note the car has had new vacuum hoses so wonder if they have been put on wrongly.

[philipayton]

Comparing what I have to the manual I have one initial question. The air intake has two vacuum inlet/outlets. One goes to the air intake duct (temp regulator) but where should the other one go (mine currently routed to the vacuum reservoir which is wrong). Can’t find this in the manual in diagrams or photos. Thanks

[GT_II]

I'll check that out later today

[philipayton]

Thank you

[philipayton]

I’ve routed the vacuum circuit according to the manual - subject to that outlet/inlet on the air intake (as above) just blocked off for now.

It ran just the same! Which is a surprise given how much was wrongly connected. Only on start up was it a little less smooth. Still hesitating when hot.

Probably need to start by cleaning the carb / jets and finding where the missing vacuum pipe goes.

[philipayton]

Plugs look the right colour.
One of the jets seemed a bit dirty but could have been a bit of fuel.

[philipayton]

Just run it again and no improvement. I have noticed there is oil at the bottom of the carb where it meets the inlet manifold. Assume that’s not right?

[GT_II]

The air intake has two vacuum inlet/outlets. One goes to the air intake duct (temp regulator) but where should the other one go (mine currently routed to the vacuum reservoir which is wrong). Can’t find this in the manual in diagrams or photos. Thanks

The schematic diagram in the VW workshop manual for Scirocco carb and ignition systems shows a vacuum hose emerging from the rear of the 2B carb (the only vacuum port on this side of the carb) for connection to the air filter. Unfortunately there are no pictures of the rear of the carb to show where this port is located. The colour coding ring for this hose is "natural", which I take it would mean translucent pale beige.

I’ve routed the vacuum circuit according to the manual - subject to that outlet/inlet on the air intake (as above) just blocked off for now.

I'm thinking with the air intake vacuum hose blocked off this means there is no vacuum to open the air intake flap so the carb is taking in pre-heated air only, regardless of the temperature. In hot weather like now the temperature regulator on the air box should allow vacuum from the carb to pass through to the flap switching the air intake over to cold air only.

[philipayton]

Thank you.
Do you know which of the two hose ports each line goes to? I.e. does the one operating the air intake flap go to the front port on the air inlet box) and the hose from the rear of the carb to the rear port?

[philipayton]

Also, according to the Haynes manual the vacuum port on the rear of the carb goes to the econometer. Unless there’s a second port?