I have been having problems with fuel supply (I think) for about 2 months now.
The van has an intermittant missfire which occasionaly stops the engine.
I changed the fuel filter and thought I had fixed it for about 60 miles
until it came back.  Then I thought it was water in the fuel because it
seemed to stop when I used gas dryer.  Lastly I swapped out the fuel
pump with another that I had lying arround.  The symptom has not
come back for about 600 miles but the "new" pump is making some wierd noises.
It sounds like there are air bubbles going through it. In fact if I look 
at the fuel filter I can see air bubles inside of it on the pump side.  Is
this normal, does it imply a suction leak (no gas leaks out), is the pump
leaking air into the fuel, should I try to get rid of it (difficult)?
Any ideas?

Thanks
 

--
David Shepherdson