g23crawler

Having a weird issue and hoping im just overlooking something. I installed a new fuel system and my FPR wont hold pressure. On first start up the gauge read around 90psi, adjusted it down to 58psi and car ran great. Went to start it up about 4 hours later and the gauge showed around 90 again. So adjusted it back down, let the car cool down and it did the same thing. I am using an electronic gauge, I will put a mechanical one on tonight to verify but I know the electronic gauge is good. Its like once the car cools down or the fuel drains back to the tank the fpr losses its adjustment (which I dont even know how that would be possible) using an aeromotive FPR, walbro 450 intank, a1000 external, 10an feed, 8an return (flex fuel sensor in the return), holley fuel rails. Crappy pic of how I have it routed now. Also the a1000 is not active right now, until I figure out this issue.

mykream

Did you block off the stock fpr?

g23crawler

no because my fpr isn’t boost referenced, I was told I didn’t need to block it off if it isn’t referenced. I’m running a base 58psi.

mykream

Hmm, I have always heard to block it off if you are going to an external regardless

Turpid porpoise

Is all fuel from the return line flowing through the flex sensor or do you have a bypass loop going around it for excess flow?

g23crawler

Its currently all ran through the sensor, but I had the sensors on when all I had was a 450 intake and it was fine.

Turpid porpoise

Have you disassembled the FPR to clean it and check for damage to the diaphragm?

g23crawler

No but I will tonight, I was just curious on why the pressure fluctuates as the car runs longer. I will take out the sensor to see if that doesn't change anything also. I just figured if it was the sensor it would be a constant pressure I couldn't adjust.

Unreal

Flex fuel sensor isn't an issue. Sounds like FPR is bad. Try swapping it out.

As for block off the factory regs, you don't have to do it to keep siphon working if you keep pressure up at stock levels, but you may overrun them which could be an issue. Then again it would have been an issue before this.

g23crawler

Took it apart and it looked perfec. There was a hose barb on the boost reference port, took that off and put a manual gauge on. Hold 58psi perfectly fine now. Not sure if it was the electronic gauge or that hose fitting. Just glad it works now.