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To coin Bodgers phrase HELP

My 300 tdi disco has started destroying lift pumps, 3 in 3 weeks, anybody got any advice on this, there's no muck or water in the system and when you crack the pipes after it's failed there's a hiss like it's formed a vacuum. Thanks for any replies.

Which replacement pumps have you used? Some of the aftermarket stuff is very poor quality I've heard of several people having problems with Britpart stuff.

Delphi which aren't bad. The one that's on now feels a bit dodgy, I'm fitting an in line filter today in an attempt to at least eliminate one potential problem. If it happens again everything will be stripped cleaned and/or replaced from the stack pipe forward.  

A quick addition to the info available, I re tested the pump I took off which definitely wasn't working is now working again. So the question now is why would it stop working for a while, is there a valve that could get clogged?  

Do you think that the supply pipe from the fuel tank is blocked or a foreign body is blocking the tank outlet. is there a kinked or trapped pipe from the fuel tank. A failed pump does not usually form a vacuum at the pipe connections. your description would suggest the pump is fine it is the pipe work at fault.

Another check is to see if the fuel tank breather is clear, if air cannot enter the tank as fuel is used this will cause a vacuum greater than the pump can overcome.

It does sound like you might have some plumbing issues rather than the pump being at fault.

Sorry I should have been clearer the pump was taken off and a clean pipe attached to the inlet and dropped into a jar of clean diesel and both the cam arm pumped and the primer arm pumped and it wouldn't suck diesel. The same test on a new pump and it drew diesel through in 2 pumps. I re tested the duff pump after a week and lo and behold the damn thing worked. The fuel pipes have been checked and no kinks or blockages.
I was going to put an inline filter on yesterday but the connections on the filter weren't big enough to get a tight seal so I'll try to find a better one today.
I also had a spare brand new sender unit so I stuck that on too.
Is there a non return valve in the pump body which might get stuck?
The filler cap is a push in plastic thing so it's not air tight.
It's a bit of a puzzle but I will persevere    
shropshire bill

Have you checked the sedimenter filter ?

I had problems with mine when running on used veg oil

I chopped that out in the first couple of months I had it. All they do is fill with much and water and cause problems. The filter does all of that anyway, the landy guys all agree it's a waste of time. At the moment every day I just release the bleeder nut in the filter and check the gauze at the top of the lift pump and so far so good.  

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