Thread: low fuel pressure

hey guys i wanted to start this thread because i think it is going to help me diagnose my car and i think it would be good to know. Name any and as much reasons, you know that can cause your fuel pressure to drop. thanks guys

dirty fuel filter
bad fpr
bad fuel pump relay
bad fuel pump
dirty fuel pump sock(filter)
dirty fuel lines
poor voltage at the fuel pump

those are good...how would a bad relay cause low pressure? sorry if that is a noob question

it pretty common for the the relay to cause issues. if you check the voltage at the pump and its less than 12v at idle thats your problem. One of my friends used to work for nissan and told me that nissan regulated the voltage to the pump at idle and other driving conditions but I could never find this in the fsm. I have on checked the voltage at the pump in a few cars and seen 9v and only 11v when reved up. I usually add a external relay to cure this.

here are things that will increase fuel pressure
walboro pump 2-4psi
300zx tt fuel filter 2-3psi
external relay to pump 3-4psi

I did my fuel upgrade in steps so I know how much my pressure changed with each part.

so you just rewired a whole another relay for the pump?

yep 40a bosch relay wired to the pump harness out side the tank. wired to the battery and triggered by the factory switch. I now see 12-14v at the pump harness.

So, i checked the voltage at the connector for the fuel pump and it read 11.94v with the key on engine off. Then about 2-3 seconds after it went straight to 0v. Is that normal i mean i don't think so but i could be wrong. thank you guys for the help.

yes the pump will prime for starting then drop off. You need to check the voltage with the car started.