Airlock?

[texasuk]

I have a constantly recurring problem, where my van seems to create an airlock that stops fuel getting through when parked up for a while.
To get it going again I seem to just have to remove the inlet fuel hose for a second, which then seems to allow fuel to flow again. I used to blow down the pipe, but it doesn't seem to need this anymore, if it did to begin with. Once when I took the hose off I heard a rush of air, as you would expect to hear when a vacuum has been released, which is why I use the word 'airlock'.
The problem is I can't seem to work out how it is happening or what to do to fix it. I don't hear a rush of air when taking the tank cap off when it happens, so it doesn't seem to be caused by the tank not being vented, although I haven't checked any pipes down there yet.

Has anyone else come across the problem? Standard 1.9DG.

[kevtherev]

Can we assume you have changed the filter,
made sure the fuel line is not kinked..
and checked the pump operation is all good?

[texasuk]

HI Kev, thanks for the reply and yes, all three are correctly assumed.
The fuel pump was replaced with known good (and a few thou longer rod), the filter was replaced with new and the fuel line is routed well.

I think it may happen more frequently when the tank is low on fuel, but can't be sure. I wish I could work out wht it is, I'm baffled to be honest. Does anyone know if the non-return valve in the overflow/return system might have something to do with it?