tehzack
New Member
I've been chasing an issue where my car (2001 GT 5spd: ported heads, MHS 2.5 cams, longtubes, full exhaust, etc) falls on its face momentarily after upshifts at WOT. I've done some reading and it seems like the PPRV after the fuel pump can cause this issue. I dropped the fuel tank to do the pprv delete. While I was in there I installed a Deatschwerks 340 fuel pump since I figured an OEM pump lived there and I wanted to bump the spray up to 125/150 from the 100 I've been running.
When I initially cold start the car it will run normally until it gets some temperature. Once it starts to warm up the car will buck and shake and just barely be driveable. I logged the fuel pressure in HP Tuners and it fluctuates wildly from like 0-80psi while its bucking (with corresponding wild swings in AFR's). I dropped the tank again to confirm that the feed line running from the pump directly to the tank wasn't kinked and to make sure the pump ground wire wasn't pinched in the fuel hat causing it to run at max pressure. Everything looks fine.
I tried unplugging the fuel rail pressure sensor and the car runs perfectly fine. AFR's are perfect: Idle/cruise is 14.7 or so, WOT 12.8-13.0 (Car is N/A), no bucking and the split second lag after upshifts is gone. When I pulled the vacuum line off the FRPS no fuel came out, and from what I can tell when datalogging fuel pressure it seems to work fine.
Everything I've read lead me to believe I could just drop this pump in and go on my merry way. Since I've also deleted the PPRV would running a fuel pump this large require some tuning on the stock fuel pump voltage values in HP Tuners or something? What does the car fail safe with the FRPS unplugged that would make it run like normal, but be barely driveable with it plugged in?
I've got an oem FRPS and one of those kenne bell restrictor disc deals ordered to try and install and see if maybe that makes it happy again. Got any suggestions to offer in addition to this? I've been thinking maybe the fuel pump voltage might need to be tuned, but it doesn't seem like anyone else has had to do this with this size pump.
When I initially cold start the car it will run normally until it gets some temperature. Once it starts to warm up the car will buck and shake and just barely be driveable. I logged the fuel pressure in HP Tuners and it fluctuates wildly from like 0-80psi while its bucking (with corresponding wild swings in AFR's). I dropped the tank again to confirm that the feed line running from the pump directly to the tank wasn't kinked and to make sure the pump ground wire wasn't pinched in the fuel hat causing it to run at max pressure. Everything looks fine.
I tried unplugging the fuel rail pressure sensor and the car runs perfectly fine. AFR's are perfect: Idle/cruise is 14.7 or so, WOT 12.8-13.0 (Car is N/A), no bucking and the split second lag after upshifts is gone. When I pulled the vacuum line off the FRPS no fuel came out, and from what I can tell when datalogging fuel pressure it seems to work fine.
Everything I've read lead me to believe I could just drop this pump in and go on my merry way. Since I've also deleted the PPRV would running a fuel pump this large require some tuning on the stock fuel pump voltage values in HP Tuners or something? What does the car fail safe with the FRPS unplugged that would make it run like normal, but be barely driveable with it plugged in?
I've got an oem FRPS and one of those kenne bell restrictor disc deals ordered to try and install and see if maybe that makes it happy again. Got any suggestions to offer in addition to this? I've been thinking maybe the fuel pump voltage might need to be tuned, but it doesn't seem like anyone else has had to do this with this size pump.
