WG start then stall ?? faulty lift pump

[JimmyJ]

Thank you kindly Offroadroad Spike. Yes it's the 2.7.

I had changed the fuel filter about 6 months ago just because it was due. Fired up straight away using the bleed valve, had no air, and ran fine up until recently.
Changed the filter again just in case, tightened up all the hose clamps, same bleeding procedure but the fault remained.
There is no rough idle once it starts, it runs fine once it's going but I can see bubbles in the small line between the two pumps. I have about a 30-minute window where it will restart again normally but that's about it.

I have picked up the green o'rings from the local Mercedes van dealership and ordered a new line that includes the bleed valve as the push-back clip is looking a bit dodgy so figured I might as well change that as well. Hopefully, that will be here in a couple of days so we shall see. Also going to replace the small hose on the back of the filter so fingers crossed.
Thank you again

[Deezelweazel]

May i ask which type of fuel filter you use?

The one with the return valve and three fuel line connections( two with the o-rings and the additional plastic thermostat) or the one with two connectors with a direct return without leading back to the filter?

[JimmyJ]

Thanks for your reply Deezelweazel,
It was changed from the original one by the workshop that did the injectors (and a multitude of other things). It's a Cooper filter WCF78 so just the one direct return line. For the first time, I did actually see a tiny bit of diesel sitting on top of the filter. There hasn't been any up until now but it had been sitting for two days so no idea if that made any difference
The car no longer fires after cranking now

I've changed the o rings on that line and the one between the lift and high-pressure pumps but the push-back clip on the bleed valve has broken now so I can't get the plug out. I'd rather not just try and crank it as I think I've killed the battery. Seems to only be cranking on 9V so waiting for the post and the new bleed valve line.

[Deezelweazel]

Bleed valve?
Are you talking about the one with the plug close to the fuel rail? Never used that one.
Maybe you get a small manual lift pump like the ones Bosch sold in the past.
With that one you can very conveniently purge the fuel filter if you open the drain on the fuel filter. It has a small anti drainback valve installed in the pump. Once the fuel is in the filter it will remain there.

Another cause for the constant drain could be a missing fuel line in the fuel tank. The feeding and the return line must reach to the bottom of the tank. If the return line is missing, it will drain the line automaticallly.

[JimmyJ]

Yes, the bleed valve near the fuel rail. Every time I've changed the filter I've been able to start the car first pop by filling the filter and using the valve.
sorry, I'm unsure of what you mean by a missing fuel line. The car has been running with this setup for the last 6yrs

[Deezelweazel]

In the fuel tank there is a fuel line camped to the the return line. This line must reach also to the bottom of the fuel tank. Otherwise it will drain the return line, causing trouble. The fuel injectors release the excess fuel into the return line. If air is in this line it causes trouble.
The injectors need to work against the non pressurized amount of fuel in the fuel return line. If air is in this line you don't have that "backpressure".

[JimmyJ]

Yay we're running again.

I'm not exactly sure which one was the problem.

Changed the O'rings on the filter clip and both pumps but still no go. Bought a new battery just in case. Probably didn't need it though.

Managed to get the broken clip on the bleed valve off finally (the new one is stuck on a wharf somewhere). A terminal amount of time is spent bleeding the air out. Still no fire so cracked injector and no fuel up getting there.

Bypass fuel filter and she fired out of a bucket of diesel.

Switch filter back to Wilson brand instead of the new Ryco one as the clip fitted better and changed the hose from the filter back to the steel fuel line.


Success!!!!!
Pretty sure it was a combo of the filter clip and hose that was the issue.

Thank you so much for everybody's responses and the willingness to share your wisdom.