cliffyk

I looked in the shop manual last evening and also saw no mention of back probing--I was curious as to what source you had that suggested it.

You state the "battery is good". How was that determined? Checking the voltage while cranking, monitoring the voltage as suggest by JayC, high load testing?

I think you are beyond what can be done with a multimeter and need to find a shop with a diagnostic 'scope than can monitor the actual signals between the PCM and the FPD and analyze the duty cycles of the input and output signals along with the fuel pump voltage and current draw...

JayC

[QUOTE=cliffyk;8145498]I looked in the shop manual last evening and also saw no mention of back probing--I was curious as to what source you had that suggested it.

You state the "battery is good". How was that determined? Checking the voltage while cranking, monitoring the voltage as suggest by JayC, high load testing?

I think you are beyond what can be done with a multimeter and need to find a shop with a diagnostic 'scope than can monitor the actual signals between the PCM and the FPD and analyze the duty cycles of the input and output signals along with the fuel pump voltage and current draw...[/QUOTE
Yeah my battery was good as well. Never ran down and always started in the coldest weather. But it would not handle the sustained current draw of a Focus pump
with a 20A BAP.

Bman2000

http://www.allfordmustangs.com/forum...fpdm-check.png

this is what i found. i didnt use this one, but looks like the same problem tree print out from the dealer, which i got and have sitting in the trunk of the car. says disconnect fpdm then test power pin and ground pin from the connector. no back probing like i said, which i thought was weird cuz i wasn't sure how a harness not connected to the actual part would give you an answer about the part being bad?

In any case, i didnt use just a volt meter. we had a volt meter to verify the the voltage was getting from the fpdm to the pump, and we used a scope i guess its called? i thought they were just big hand held things, cant remember the technical term i guess, but basically like a tech 2 and that's where we monitored signal from the pcm to fpdm and so on, along with other stuff. So fpdm is bad. As far as the battery i guess i could recheck but its only a little over a year old, but yea i was kinda going off the hey it works great for starting so must be good and strong lol. guess that's not scientific.

edit: by the way that tech 2ish thing did a koeo test and thats the first place the fpdm had a failure code. Then we watched fprs and the voltage signal and the actual signal and when the car fell on its face the rail pressure went from 38-40ish to 26 and the voltage dropped to 10v on the volt meter after the fpdm and the signal from the pcm was still 100%

Bman2000

Also im looking at replacing it, was just going to use a factory unit, but i see for a little more they have upgraded fpdm that are supposed to be less prone to thermal issues that can cause a lean in the system when being used really hard, and i am running a ford gt pump (310 lph) i see they say to use those when running the dual fpdm dual gt pumps, but just curious do you think it may be worth paying a little extra for that since i have to replace it anyway? or on my set up not likely to help at all?

Bman2000

by the way cliff, i know i said back probing in the first post, i just meant check the pins in the connector, since it was disconnected i just call it back probing.

JayC

Is it possible to find a friend with a good working FPDM that you can borrow long enough to test things out. What you're describing is exactly what we saw. Signal to the FPDM was 100% but the voltage dropped as the load when up.

cliffyk

That's what I thought.

Back probing is a common term/process in electrical testing, however it is as I described above, using thin wire probes to go in through the "back" of a connector...

Bman2000

jayc i dont know anyone else with another fpdm anymore. Im kinda stuck buying it. Also im running a single ford gt pump no bap, from what i understand our fpdm usually can handle around 20A before have a thermal shut down issue, and running 2 ford gt pumps pulls around 25A so with a single and no bap im under the impression i wont have that issue. But its easy enough to test. so ill order the part but before i plug it in when the car is back at the shop ill test the battery.