Air in fuel lines - poor starting

[Winchweight]

There is a significant amount of air in the two plastic fuel lines between the fuel pump and the fuel filter.

The fuel lines from the tank were replaced two years ago, the lines on top of the engine are all in good order with no signs of leakage, the engine block is dry (except for a little oil which is another story), the rubber cap on the end is brand new.

The plastic lines don't appear to be cracked but they are very hard and somewhat brittle. Again, no obvious signs of leakage. Will run engine when BB home to see if anything escapes under pump pressure.



Any suggestions in the meantime?

[Winchweight]

Ok. So. After turning over on the starter the engine eventually fires and quickly the air in the return line ceased. But the feed line from the filter to the pump was full of air and a bit of froth, which to me seemed to be originating from the fuel filter end of the plastic pipe ( the bit with the crimped ferrule). I could see it creating bubbles there.

This bit.



I'm guessing I need to replace the pipes at the fuel filter. It's an AFN Tdi conversion, so does anyone have the part number please? Also looking at the picture, is this how it should be arranged or is there a better way with fewer crimps, jubilee clips and pipe joins?

[marlinowner]

It would be a good idea to replace the jubilee clips with proper fuel pipe clips, jubilee clips don't work very well on small diameters and might not be airtight.

[MGP]

Replace the thermo valve on the top of the filter, the white part held in with the R clip.

Sent from my SM-G920F using Tapatalk

[Oldiebut goodie]

The diameters of the rubber hoses (with the jubilee clips) look too large to me.

[Winchweight]

Cool thanks chaps. I'm going to replace the fuel filter (Fram) and the thermovalve. Also the jubilee clips with fuel clips. The hoses are from BW so I'm hoping they're good. If BW have the plastic pipes I'll do those too.

[syncroandy]

The o-ring on that plastic union thing is prone to leaking apparently, you might try renewing it first to see if it stops your air ingress. I replaced the whole union when I put in my TDI just to be on the safe side. TBH though I think you're right to suspect the clear fuel line with the swaged on hose. It looks like someone has already shortened it possibly to deal with splitting at the end. Re. clips, I grab nice OEM fuel hose clips when I'm at the scrappers, no excuse for having various random jubilee clips.

PS. Soz, just re-read and saw you mentioned the thermovalve.

[Winchweight]

Order some fuel clips from BW too. Will have to phone them to ask about the plastic lines as I couldn't find them on BW.

[syncroandy]

I'm sure they can do you a replacement clear fuel line, they invested in a proper machine to do the ends. Email sales if you can't find it on the webshop.

[GavB95]

I've just had the same problem on my van so I've replaced all the rubber hoses and also the black polymide tube that runs under the van (bought from brickwerks). I got the correct mini-type fuel hose clamps from Auto Silicone hoses (10mm-12mm dia for the return and 12-14mm for the feed side).

That swaged on fitting on the feed pipe had been cut down quite short on mine and looked perished. I cut the swaged metal cap away which leaves a brass insert inside the clear pipe that you can clamp a new rubber hose to. It doesn't need the swaged bit really.

Before...


Cutting (cut off the van)...


Brass insert revealed...


I replaced the filter, thermo valve and clip on mine too. Problem now solved and not seeing any bubbles in there anymore.

[GavB95]

Pic of the fuel filter with new lines/stainless clamps...


Brickwerks do the clear feed line:

https://www.brickwerks.co.uk/t3-parts/t ... -pump.html" onclick="window.open(this.href);return false;

If they make them should be able to do you a length of the clear pipe to make your own return - I wish I'd replaced them on mine tbh as they're very discoloured.

[syncroandy]

[Winchweight]

Excellent, thanks very much chap!

Gav, thank you for the pics, it's much clearer now.

[Winchweight]

All sorted. New filter, thermovalve and hose clips (replaced jubilee clips with fuel,hose clips).

[GavB95]

Happy days, good to hear that you've fixed it.