crashmymax

iTrader: (1)

I'm assuming this is the fuel pressure sensor. Will not having this plumbed in to my new fuel lines cause the pump not to turn on?

Three6GMC

iTrader: (11)

Yep thats the fuel pressure sensor. Do you have a flex fuel truck and still running the fuel pressure control module? If you do then possibly as the FPCM constantly reads fuel pressure to adjust fuel pump PWM. I would imagine if it didn’t see fuel pressure then it wouldnt run the pump. If your running a fuel pump straight power/ground then no.

crashmymax

iTrader: (1)

Thanks for the reply. I do have a flex fuel truck and am running the FPCM. Is there any reason to continue using it? Is there a way to bypass it and keep the factory pump wiring, fuse, relay all working normally? Should I just wire in new relay and fuse like I did for my pumps in the surge tank? thanks

crashmymax

iTrader: (1)

I guess it would help if I explained my setup a little. I kept my factory pump to feed a surge tank with 2 walbro 450s it is a return style now. I removed the filter and what I think was the fuel pressure regulator from the stock sending unit because I figured it would interfere with the after market FPR. I left all the wiring the same for the factory pump other then I connect the signal wire for the 2 new pumps to the large gray wire at the FPCM connector forgot the pin #.
Link to picture of what I removed from sending unit
https://www.performancetrucks.net/fo...-549168/page6/

crashmymax

iTrader: (1)

found your thread on gmt 900 fuel pump looks like I need to move the signal wire for my 2 new pumps from pin 47 to pin 13 to trigger the new relays. Not sure that has anything to do with the stock pump not running but ill fix that and see.

crashmymax

iTrader: (1)

I am not getting power to the fuel pump signal relay at the ECM pin#50 DRK GRN/ WHT. I do have continuity between pin 50 at the ECM and pin 13 at the FSCM. Anyone know what wire should supply power so I can do more test.

Three6GMC

iTrader: (11)

First off check the fuse for the fscm think it’s number 21 should be a 25 or 30 amp fuse. Next pull the connector off the FPCM in the rear of the truck and test the two #10 wires both on the same end of the connector to see if you have power, those are your main power and ground. Next once you are sure you have power and ground there follow on my build page how to wire in a relay and get rid of all that surge tank junk and you will be good to go.

Three6GMC

iTrader: (11)

Also being a truck with a FPCM I don’t believe the ecm puts out a signal to the fuel pump relay in the fuse box, not 100% sure though but on my truck the relay wasn’t even there. Tried to see if I could get a signal off the pins and got nothing either. I got all my signal, power, and fuel pump wires straight from the FPCM connector

crashmymax

iTrader: (1)

There is no fuel pump relay in our trucks the FSCM acts in place of a relay. You used pin 13 at the FSCM to trigger your relay and you need power to pin 13 when the key is in the on position. I have no power at pin 13 so pump will not turn on. I traced the wire from pin 13 (dark green/white stripe) to the ECM pin 50. I should have 12v at pin 50 but have nothing. So I have no idea why I don't have 12v with the key on at pin 50 not sure what to do next. I am checking with tuner to see if its possible that not having a fuel pressure sensor installed is preventing pin 50 from getting power but I doubt it. Also both fuses are good, I ran the pump works fine.

crashmymax

iTrader: (1)

Do you know if the ECM has it's on fuse or relay? I'm going to pull every fuse tomorrow and make it's not something that simple. Is there a way to test an ECM? Trying to figure out some test to do tomorrow.