Just installed a Walbro 255. Pump sounded really odd and it would not build any pressure. Sounded like it was free wheeling. Wiring was double checked to make sure polarity wasn't the issue and then the assembly was taken outof the car. I connected the pump to a 12v source and again it sounded weak. Minimal suction from the sock and no pumping out of the top. Pulled the pump completely out of the housing and removed the sock. Reconnected the wires and put my finger over the outlet side. Very little if any pressure, but began to make normal pumping sounds and pressure started to come up. There was a definate pumping sound now present with my finger off of the outlet and I could feel it as well Squirted some gas into the inlet and connected again. This time it blew gas out of the top and had a very good suction from the inlet. Now the pump seems OK but I do not want to install a sketchy pump. Anyone ever experienced this?

 

Make sure you have the rubber grommet between the FP and The FP housing. It just sits between the them and the compression of the FP into the housing swells it to complete the seal. Also check to see if the grommet has been ripped.

 

I figured it out. I'm gonna make another post about the issue. It's specifically related to Full Blown dual pump set ups.