Bman2000

so i tested my fpdm the way it tells you to from the factory by back probing the harness, and i believe since i dont have paper work in front of me it says if you test these 2 wires you should have less than 10.5 volts, if you have more replace fpdm. sounds simple enough except how would probing the harness while its unplugged from the fpdm give you an accurate answer about the fpdm not working? i mean no other wires connect to it, so technically i could replace the fpdm 30 times and have the same reading. Am i missing something? because my fpdm "tested" bad but that test makes no sense to me so at the moment i refuse to waste money fixing it. Help!

WhiteFoxGT

can you tell me what code you are testing for...if no code, is the fuel pump inop? What pinpoint test are you following?

Bman2000

no codes. vortech supercharged car running out of fuel up top. Basically im just going through the whole fuel systems to try and find why im running out, since the tuner hasn't said anything about need a bigger system and im running a ford gt pump and its running out of fuel at 337 rwhp with no timing. testing fpdm power pin and ground in the harness like it says. Unless im supposed to be tapping into the wires and test through the fpdm which would make more sense, but that is not how the test tells you to do it.

edit: fuel pump was brand new, car runs fine makes hp, just doesn't have enough fuel up top. 5200 rpm spikes rich 10.5 to 1(i can only assume because the car detects it starting to lean out) then 5500 falls flat on its face 15-17 to 1 and leaner since it can no longer keep up

cliffyk

"Back probing" means measuring a value with all connections in place and the system under test powered--not disconnected. It refers to the physical act of inserting probes into the "back" of a connector to make contact with the connector terminals/pins.

Back probing can be a PITA on some connectors so generally I use insulation piercing probes--specifically these:



They make a very small puncture, that does no serious damage to the insulation and is almost self-healing--I do put a dab of dielectric grease on the "wound" if it's something I know I'll be back to in a bit--otherwise use a dab of RTV sealant...

99 GT vert

If you are running out of fuel up top it sounds like a tuner issue not a fuel pump issue with the power level you are at. I had the same thing happen on my cobra I was running out of fuel over 5500 with 3-300 lph fuel pumps and a return style fuel system. I switched tuners and have not had a problem since.

JayC

Are you data-logging battery voltage? I had the same type problem went my 5 year old battery decided to take a **** during a dyno session. We installed a fresh new battery and the problem was gone. Just a thought. Good luck with it

cliffyk

It is a good thought too, flat out high-capacity fuel pumps can easily draw 18 to 20A each, and the generator will shut down at very high revs...

WhiteFoxGT

I've also seen the frp sensors fail on boosted applications. Quite common

cliffyk

^+1...

Bman2000

Thanks everyone. The battery is good, the fps is also testing good. Now as far as back probing the test from the ford manual says disconnect fpdm then test power and ground pin. the way its layed out seems to tell me not to back probe it. Thats why i wasnt back probing it, just confusing. But beside the point now, i ran a full modis handheld and back probed the signal between the fpdm and pump. Its flaky but the fpdm is failing. Upper rpm its dropping voltage instead of maintaining the 12.5 or whatever the max was, it dropped a few times to 10 volts. Plus the fpdm failed its KOEO start up test that the handheld did. Oddly enough sent a code to the hand held but whatever is wrong isnt enough to actually set off the cel and leave a hard code. But im starting there hoping that fixes the problem completely instead of just part of the issue