Fuel pump issue!

[Brandon H]

I have a dual pump division x return fuel system. The car drives great when the fuel pump comes on with the ignition and has never died while driving. I noticed after driving I will go to turn the car off and when I go to turn it back on, the fuel pump will not come on with the ignition(no priming or running). There are zero fuses blown, fuel pump relays are good, but the aux fuel pump relay will not come on. I bypassed the inertia switch to make sure that’s not the issue. I disconnected the negative terminal from the battery and reconnected it and the fuel pump comes right back on with ignition. Each time the pump doesn’t come on, I disconnect the battery and reconnect and bam it’s good to go.. Any ideas? I’m stumped.

Edit, FPDMS are bypassed, all the wires are cut except the two middle ones that go to the PCM

 

[86GT351]

Hook up the FPDM and see what happens

 

[Cum Grano Salis]

Just a few thoughts-
1) If pressures are high enough, what shuts both pumps off? Those would be a positive liquid displacement operation, pressure switch(es) required?
2) Is it auxiliary pump only not activating (always did before) not clear? Possibly 2 stage intervention related to fuel requirements, it’s not supposed to.
3) Know nothing about GT 500 theology. Only familiar with Scully Control and JP-8 commercial type fuel dispensation. Just sayin’.

 

[01yellerCobra]

Are both pumps set up to run 100% of the time? The next time they don't come on tap the relay.

 

[Andrey Sidorov]

So I have similar setup on my car - division x fuel rails and return kit , with aermotive fpr, fpdm bypassed with wires cut , what let’s the pump go on is the relay that is fed from direct 12v from battery and ignition 12v from key turn source (runs all the time when the key is in on position) I had an issue where the pump would not turn some times - the issue was a bad relay. It sounds like In your case it’s getting stuck in off position after it disengages for some reason. Check the relay and check the wire to ignition source , in my case that relay is under the rear seat on the driver side , your case might be a bit different