Renault master fuel problem?

cdc, thanks for replying, it does run fine, its just on start up hot or cold, just had new glow plugs because the dashboard light for these was staying on all the time, its now reset and clear. the van will start up every time but when its playing up the revs will slowly drop and the engine will stop after about 10-15 seconds, its very hard to re-start at this stage, this when i can see an empty fuel line (just air) between the filter and engine, squeezing the primer bulb about 10 times will re-fill most of the line and the engine will start on the second try. Thanks again.