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 Second vacuum on carb?
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UK_Sub
V4 Guru

United Kingdom
2337 Posts

Posted - 26 Sep 2021 :  18:59:34 Show Profile Reply with Quote
I was trying to start up a 96 that had been dormant for 6 years - fitted the dizzy, rigged up a petrol can and the car would run, but belch out flames from the carb.

Realised I could hear sucking noise, which turned out to be coming from a second vacuum pipe coming out of the carb base. As soon as I blocked this, the engine sprang into life and idled perfectly.

I know one of the vacuum pipes was for the brake servo, but what is this second one for - does it link to the pipe on the rocker cover?


Edited by - UK_Sub on 26 Sep 2021 19:00:48

christophe
V4 Fan

France
127 Posts

Posted - 26 Sep 2021 :  20:02:09 Show Profile Reply with Quote
Yes, the second pipe is used for the PCV system. There is a check ball inside the conduit from the carb for this one. I am not 100% sure and can't have a look under my bonnet right now, but I am wondering if the hose from the brake servo is connected to the right outlet there. On my car, these had been switched by some shade tree mechanic.
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Borstlap
V4 Fanatic

Norway
304 Posts

Posted - 26 Sep 2021 :  20:25:18 Show Profile Reply with Quote
The brake booster is on the wrong side, the pcv hose coming from the rocker cover should be connected there. That 90 degree connection should be straight up with the hose to the brake booster attached.

Alex
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UK_Sub
V4 Guru

United Kingdom
2337 Posts

Posted - 26 Sep 2021 :  20:33:03 Show Profile Reply with Quote
Thank you for your quick replies!

Does that mean the vacuum on the left (currently linked to the brake booster), should go to the oil breather pipe instead?
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christophe
V4 Fan

France
127 Posts

Posted - 26 Sep 2021 :  22:50:16 Show Profile Reply with Quote
Yep! That's it.
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72sonett3
V4 Fanatic

Spain
264 Posts

Posted - 16 Oct 2021 :  22:40:40 Show Profile Reply with Quote
But there should also be a Positive Crankcase Ventilation (PCV) valve between the nipple and the valve cover.

--
'72 97
'77 96L conv.
'95 900SE conv.
'99 9-3T
? 006
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