New Lift Pump/ Weird Problem

[pwr2tow]

I just finished putting in lift pump #4 and thought I would put my pressure gauge sending units in a different place. I put a petcock in the sending unit line so I could bleed air out of fuel lines, which would come in handy when I change fuel filters oorrr pumps . Well I went to do the bump the starter thing to make lift pump run and purge air, The first time was O. K. and pressure was O. K. , then I thought well do it again to make sure all air is out of system. The second time I bumped the starter the pump runs but no fuel and no pressure, I do this again and still no fuel and no pressure, I do it a few more times and still no fuel and no pressure. I didn't know what to do so I start truck and guess what I have fuel pressure and when I open petcock fuel runs out and truck is running. I shut truck off and bump starter, no fuel and no fuel pressure.



What could cause the pump to run but not pump fuel.

There are no air leaks cause the system holds pressure (according to gauges) until I bump starter then the pressure drops to zero unless I start the truck then pressure stays at 13lbs.



I disconnected the batteries again and went inside for lunch and when I hooked the batteries back up and bumped starter it pumped fuel and I had pressure, bumped starter second time and no pressure or fuel. Started truck and runs fine, I have pressure and fuel flow from petcock while running but not when I bump starter.



This really has me frustrated, as if haveing to change lift pumps every 10,000 miles isn't enough.



Any ideas???

Ron

 

[Brandon]

change polartity

 

[pwr2tow]

How do I change polarity when it is a connector plug??

Please explain? I do not understand. The lift pump pumps fuel when the truck is running, and just the first time when I bump the starter. When I bump the starter after the first time the lift pump will not pump fuel but if I start the truck then the lift pump will pump fuel.

Ron

 

[pwr2tow]

I think I found the problem, The fuel system relay, I switched the horn and fuel system relay and know it works as designed. The only thing is the horn still works too. I'am going out for a drive know so hopefully this is solved.



P. S. Does anyone know how to test relays to see if there defective.



Thanks,

Ron