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fass 150 issue

1K views 9 replies 2 participants last post by  98ctd4x4 
#1 · (Edited)
Had to put a new ip on my 01 dodge, so I thought Id put a fp guage in for piece of mind. Now the pressures I get can range from 17psi at idle down to 12psi. wot hits 10. When im driving it will be at say 15psi hit a bump and it goes to 18, then a couple minutes later down to 12. So basically all over. So I put new filters on and still no change. I checked the wiring for shorts and such and all is good. So today I decided to do a bucket test and I have no fuel coming out the return line and the suction line feels like little to no suction. I can hear the pump working, even bumping the starter it runs for 30sec and pressure comes up to 15psi. So is the pump packing it in or am I missing something?truck runs and starts good. I was thinking the problem was in the tank but after the bucket test Im confused. also forgot to mention I have checked the ball and spring and and the suction line for holes and all is good.
 
#2 · (Edited)
no fuel will return unless max pressure is reached to open the bypass.
common issue is the suction line connection @ the tank. The Oring may not seal so the pump sucks air and pressure fluctuates. You can usually hear the tone change.
Is the gauge mech or elec? did you use a snubber or an isolator or both?
 
#5 · (Edited)
I checked the ball and spring on the return side and it looked fine. The fuel wasnt even moving in the bucket. It looked the same as if there were no hoses in it. It was sucking so slowly I mean a five gallon bucket of fuel with a fass150 should be gone pretty quick shouldn't it? I could feel next to no suction at all by putting my thumb over the end. I watched the video of a bucket test done at fass and it was flowing pretty good at idle. I guess the only way to see what the fuel is doing seeing how I get nothing out of the return line is Tomorrow ill take the line off at the ip and run the fass and see if the fuel is foaming or solid.
 
#6 ·
Thanks for the help turbolvr I went and picked up a new replacement pump put it on and what a difference. Truck idles at 20-21psi and at wot doesn't go below 18. The only thing I notice different from my other pump is if I bump the starter the pressure doesnt read on the guage unless the truck is started. the old pump would go up to about 15psi, but I also had no return fuel coming back to the tank on the old pump. I know I have return now because if I squeeze the return line the pressure goes up. Is this normal to not show pressure unless the truck is running? Also the new pump is about 100 times quieter, cant even hear it running when the truck is running.
 
#7 ·
The ECM should run the pump for 10 secs if you bump the starter without starting.
Mine runs the pump with just the key in "on" position so it can rev past 4k.
 
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