My fuel setup,
Walbro 255 in tank, 044 in line, 8 feed, 6 return, Weldon fpr, fuel pressure gauge on the line before the 044 (readout in car) and fuel pressure gauge on the rail.
Here's what happened, I was idling the car and noticed it sounded like the 044 was working its *** off. Looked at gauge in car and it is reading 0 pressure. This gauge if I remember right usually read around 2 bar. Shut the car down, pulled pump, cause on the dyno the sock came off and was creating issues, plumbing, wiring sock all good. I was beside the road so I had limited tools so I got a ride home and trailered the car back to the garage. I felt it might be the in tank pump (which was an aeromotive 340) and I had an extra Walbro at the house. So I changed the pump, and I'm still having the same issues. I've checked voltage at both pumps and I'm getting 13.6 at the tank and 13.4 at the 044. Car idles fine and the 044 doesn't sound like its working as hard now, but here is my issues. I'm still not showing pressure before the 044 and the pressure on the rail is 100+ psi. The base pressure for the car is supposed to be 60 psi. Other things i've tried is remove the power wire for the 044 from the battery, turn key and in tank kicks on and it shows pressure on the gauge before the 044. Hard to test this theory with the 044 hooked up cause you can't here the in tank over the 044. The relay for the 044 is getting its signal from the oem wires that are powering the in tank, and as far as I know I've got no issues from the 044 pumping other than why do I have so much pressure now at the rail and why do I have none before the 044?

 

I've also tried lowering the pressure by adjusting the fpr and it starts to go down, but car starts to stumble when the gauge gets below 80psi

 

Has to be something wrong with the 044, how much power are you making that you need all that fuel?

After pondering it more, I know you checked for voltage at both pumps, but maybe something happened and amperage is the problem.

With both hooked up, you get no pressure before the 044, and it seems like the 044 is working it's *** off. So maybe the 044 is robbing all the amperage on that circuit, not allowing the in tank to do much of anything.

You unhook the 044, and you see pressure again because now the intake has the amperage it needs.

Maybe try running a new power source to the 044 seperate from the power supply to the in tank and see what happens?

Fuel pressure might be so high at the rail because the 044 is working overtime, and the regulator cant bleed off fuel return fast enough because the 044 is pumping so hard.

Just theories, but maybe worth a shot...

 

Thanks for the info, I'll try another signal source for the 044 and just see what happens, car made 660hp/460tq. I like to keep it safe and not work my fuel system near its limits

 

Got to thinking, actual power supply (pulling amps) would be on the power supply wire coming directly from the battery to relay, relay to pump right? There is no issue turning on the 044 so I am assuming the signal wires are working as they should. Next step I'm going to try and troubleshoot the relay, but I don't understand how the relay for the 044 could be the problem, but I'll check it too. Thanks for the input, but if u or anyone else has any more troubleshooting ideas I'm all ears cause I'm not understanding why it isn't working. Thanks

 

Im having the same exact issue as you did you figure it out by any chance?