Volkswagen Passat (1988 - 1997) - 96 1.9Tdi air bubbles in diesel fuel pipe

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Tue 27 Jan 2009 19:38
96 1.9Tdi air bubbles in diesel fuel pipe - tujags
I seem to have given myself another problem I changed the fuel filter as procedure in Haynes manual but did not prefill the canister with fuel- not mentioned in Haynes- but everywhere else says fill it! thank you Mr Haynes! now when I run the engine I am getting bubbles in the pipe between the filter & the engine & the exhaust is smoky was OK before I changed filter! I have also changed the engine oil & filter. car is still offroad at present few more jobs to do before putting it back on road weather is delaying as garage is full so have to work outside.
Haynes says check for bubbles but not suggestion how to cure them if present!
No obvious leaks around filter but maybe clipped pipe connection is problem any other suggestions?

Edited by Pugugly on 29/01/2009 at 22:50

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Thu 29 Jan 2009 22:46
96 1.9Tdi Air bubbles in diesel fuel pipe - piston power
Does this have a manual pump on the fuel filter housing to bleed? is so crack open the bleed screw and pump till fresh fuel and no air come out.

Then do same between filter to pump crack off bleed screw at pump and bleed the same.

Then crack off the furthest injector and crank over engine till fuel comes out, then tighten up it should start ok.

If no filter pump you will have to crank over, but id remove filter and fill with fresh clean fuel first.
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Thu 29 Jan 2009 23:31
96 1.9Tdi Air bubbles in diesel fuel pipe - Peter.N.
Also make sure that the cannister has sealed to the 'O' ring correctly, rotating it as you tighten the bolt will help.
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Mon 2 Feb 2009 21:03
96 1.9Tdi Air bubbles in diesel fuel pipe - tujags
This is a throw away filter which has an inlet & outlet pipe which the hoses push on & then tighten hose clips & a control valve which is a sealed push fit in top of the filter it has an 'o' ring seal & an 'R' clip to retain it. The filter unit also has a drain valve on the bottom to drain any accumulated water. It ia a complete unit so doesn't fit into a housing just a clamp bracket mounted on the inner wing.
My problem is I have nearly 50 years of petrol engine experience but this is my first diesel so it's all new to me. At the moment I don't understand the function of the control valve it has hoses connected to it these are seperate to the fuel in & fuel out hoses.
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Tue 3 Feb 2009 11:48
96 1.9Tdi Air bubbles in diesel fuel pipe - dieselnut
Had a quick look at the VW Elsawin I have access to & list below the function of each of the 4 pipes to the filter :-
The one with the arrow stamped on the filter going into the filter is the feed pipe from the fuel tank.
The pipe from the T piece with O ring, going in the same direction as above pipe is the return to the fuel tank.
The pipe with arrow on the filter pointing away from the filter is the feed to the injection pump.
The pipe from the T piece with O ring, going in the same direction as above pipe is the return from the injection pump.
I don't know the purpose of the T piece other than perhaps to help get air back to the tank from the filter.
Perhaps if you connect a clear plastic tube to each of the pipes in turn you will find where the air in coming from.
It does state to always renew the T piece O ring.
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Tue 3 Feb 2009 11:51
96 1.9Tdi Air bubbles in diesel fuel pipe - dieselnut
Just found a bit more info on this control valve T piece.
Below + 15 °C:
Passageway to filter open
◆ Over + 31 °C:
Passageway to filter closed.
HTH.
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Thu 5 Feb 2009 21:30
96 1.9Tdi Air bubbles in diesel fuel pipe - tujags
Thanks for Info I didn't replace the O ring perhaps that is the problem when I can find the car under the snow I will fit a new one! & also check all the pipe connections.
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