Air Bubbles in fuel line

[peteabbott]

Right then........since fitting the 1Y engine getting on for four years ago not once have I had a problem on starting. THEN last week she turned over and over and nothing ! After checking all the usual like glow plugs etc I thought I would fit a piece of semi clear tubing from the filter to the pump. Lots of air bubbles when turning over and after she started still pulling in air. I replaced the complete fuel line from the tank and replaced the bleed back valve on the filter..........still pulling in air ! Next morning there are no puddles under her and no wet joints but the semi clear tube from filter to pump is empty so it has drained back to the tank, surely it can only do this if air is getting in ? Thinking of replacing the filter with a single in and out instead of the one with the bleed valve on, taking the spill straight back to the tank. What could do this and cause this fault "overnight" Any ideas please folks ?

[Oldiebut goodie]

Difficult to spot easily as you are dealing with negative pressure.
The way that I test for these mysterious air ingresses is to pressurize the suspect piece of fuel line with a bicycle pump and a suitably cannibalized adapter thus forcing some of the diesel out so that you can see the leak. The problem is difficult to trace as the fuel never leaks out just allows air in on suction or the fuel attempting to drain back to the tank under its own weight.
That said I have spent 10 years with my boat engine doing the same and finally cured it last year with a new fuel tank and fuel lines without ever discovering the fault, it must have been inside the fuel tank is my only thought.

[bobby-gg]

Have you got the Tdi style filter with the thermostatic valve on top?

I've just fitted a tdi and had exactly the same problem, turns out that it was the actual valve, as you've suggested, I've replaced it with a normal one in one out filter with the return straight to the tank and no more problems

Rob

[royt28]

Hi, try fitting one of these to your clear fuel pipe near to the fuel filter. http://www.ebay.co.uk/itm/170958609028? ... EBIDX%3AIT" onclick="window.open(this.href);return false;
will stop the fuel running back .

[peteabbott]

Have you got the Tdi style filter with the thermostatic valve on top?

I've just fitted a tdi and had exactly the same problem, turns out that it was the actual valve, as you've suggested, I've replaced it with a normal one in one out filter with the return straight to the tank and no more problems

Rob

Thanks everyone. Replaced the filter with a one in and out and all seems fine.

[bobby-gg]

result glad you got it sorted