HELP! Fuel pump only works on bench test, not in assembly???

[yepes281]

Okay so im having a problem with my jay racing 342 fuel pump that i cannot figure out. I bench tested the fuel pump outside of the assembly and it works flawlessly, but when i put it back in the assembly is when im having my problem. You can hear the pump turn on, but no fuel comes out. There are no leaks in the o-ring or anything. When I put my walboro back in it works fine, im only having this problem with the jay racing pump. Does anyone have any idea what it could be? Also i did switch the power and ground on the jay racing pump because the polarity is switched.
Does anyone have any idea what it could be, my cars ready to go on the dyno and this is the only thing holding me back

 

[Calan]

Sounds like a polarity issue with the pump running backwards if you are getting no fuel at all. Double-check the wiring.

 

[yepes281]

Well that's the thing I bench tested it out of the assembly, and inside the assembly, I got the polarity right, and triple checked it.

 

[Calan]

Is it rewired? Maybe the polarity has been switched in the car somehow (Or between the plug on the harness and the pump connector...on the hanger).

 

[EvoInside]

when you say you bench tested it, did you just power it up, or did you actually submerge the pickup in fuel and confirm that it actually pumps out fuel? If you only bench tested it for powering up and cycling on the bench, thats what its doing in the car, bench test it with some fuel.

 

[yepes281]

It is rewired, but when I bench tested it in the assembly, I switched the polarity both ways just to make sure I had it right.

 

[Calan]

when you say you bench tested it, did you just power it up, or did you actually submerge the pickup in fuel and confirm that it actually pumps out fuel? If you only bench tested it for powering up and cycling on the bench, thats what its doing in the car, bench test it with some fuel.

But be EXTREMELY cautious if you do this. Ignition from an electrical spark becomes a real concern in open atmosphere. I would look at using something less explosive than fuel but still pump safe myself.

 

[yepes281]

It was submerged in gas when I tested it that's how I know it pumps gas out by itself, but not while in the assembly, and im being very careful

Okay so when I hook it up directly to the pigtail harness on the fuel pump it will pump fuel, but when I connect it to white connector on top of the fuel pump assembly it wont pump, any ideas??

 

[nergsx]

It was submerged in gas when I tested it that's how I know it pumps gas out by itself, but not while in the assembly, and im being very careful

Okay so when I hook it up directly to the pigtail harness on the fuel pump it will pump fuel, but when I connect it to white connector on top of the fuel pump assembly it wont pump, any ideas??

Was the issue ever resolved having the same one in the big 26 . can get pump to work outside of the hanger but not in the hanger have tried 2 different hangers and 3 pumps with no luck

 

[19Eclipse90]

What does “outside of the hanger” mean? Please explain.

The pump physically working on the bench - which is what I assume you mean - but not when installed in the car points to a wiring or MPI control circuit issue, meaning changing either the pump or the hanger would have no effect on the result.