Pump doesnt shut off at all

[cahammer]

here is the problem we have a p-pumped 24v new p-pump and when we go to start it the pump turns on and the engine is very hard to start it doesnt matter if we let the pump run for a minute before we crank it over it is still hard starting and when it starts it runs very rough then smooths out like there was air in the lines not much just a little we also have the draw straw installed as well we were wondering if the pump is internaly regulated to shut off at a certin pressure or if we might have a bad overflow valve on the p-pump also the fass is pump only no filters and stock filter on engine block thanks for any help and no we do not have a fuel pressure guage installed as of right now

 

[White Knight]

I had this problem with my truck for a while. It turned out to be a couple of leaky fittings that would allow the fuel to drain/leak out and the pump cavity to fill with air. I originally overtightened the cheap fittings I used and they didn't seal well; I went to better fittings and it solved my problems. I would check for any leaks air or fuel and see what you find.


IIRC the FASS itself does not have an auto shut down feature. The trucks computer on the other hand may be flashed to prime the pump for a few seconds before the engine is running. Once the FASS reaches pressure there is an internal regulator that will bypass fuel, allowing the pump to continue to run.