I had an interesting problem whilst over in Suffolk the other day.
We were over there for a few magical days and were on our way to see a friend who lives there but we were somewhat early so I parked up at the side of the road for about an hour, then when I came to restart the engine, steadfastly it refused to oblige!
So ensued a few minutes of mind searching and I came to the only possible conclusion that no fuel was getting to the injectors, so I opened the bonnet and grabbed hold of the conveniently located fuel bulb/pump (so nicely placed on the Renault Master right behind the fuel filter) and pumped away only to see quite literally masses of large air bubbles in the translucent pipes.
Immediately after I had done this the engine started instantly and has continued to perform perfectly ever since!
I last changed the fuel filter 4 years and approx. 20,000 miles ago and, up until the othr day I had never had any problems, nor had I ever seen many, if any air bubbles in the pipes. But now I am at home once again I will change the filter as well as double checking all the pipe unions.