Fuel Rail Pressure Issues

[WisconsinHick1]

I am having a fuel rail pressure issue. I can hold pressure up through about 75% throttle then I try to go to 100% and my rail pressure drops in half. Can someone take a look at this log and let me know what you see?

I don't think it is my CP3 going bad. I am thinking Fuel Rail Pressure Relief Valve or my return rates on my injectors are high. But if the return rates on the injectors where high wouldn't it relieve the pressure throughout the throttle?

Log_0009.zip

[WisconsinHick1]

Sorry I'll give a little background on the truck. 02 LB7, 120% CP3, 60% injectors, FASS 150.

[GMC-2002-Dmax]

The log is useless without PW, you probably have PW too high and it's draining the rails.

Try reducing the PW at WOT by 200us and relog it, if it holds better rail pressure keep reducing it until it holds.

[WisconsinHick1]

These logs have PW.

Thanks for taking the time to look at them for me.

Log_0003.zip

[WisconsinHick1]

Also here is a log with my lowest tune.

Log_0001.zip

[LB72004]

Try reducing the PW at WOT by 200us and relog it, if it holds better rail pressure keep reducing it until it holds

I think your right. in the last log, post 5, the fuel pressure is an inverse of the PW. as the PW goes up the pressure goes down and vise versa.

[THEFERMANATOR]

Plenty of guys out there run a stock LBZ pump with 60 over injectors and can hold decent rail pressure, with a 120 over you should be able to hold just about naything those nozzles could give I would think. Need to check return rates to make sure it isn't an infamous LB7 injector going out. I know I only have 30K miles on mine and cannot hold rail pressure anymore. Also check to make sure you are actually getting fuel to the engine. From the log it looked like it built up pressure and then dropped off. Looks to me like either a leaking injector returning to much fuel, or a lack of fuel volume under load.

[WisconsinHick1]

Plenty of guys out there run a stock LBZ pump with 60 over injectors and can hold decent rail pressure, with a 120 over you should be able to hold just about naything those nozzles could give I would think. Need to check return rates to make sure it isn't an infamous LB7 injector going out. I know I only have 30K miles on mine and cannot hold rail pressure anymore. Also check to make sure you are actually getting fuel to the engine. From the log it looked like it built up pressure and then dropped off. Looks to me like either a leaking injector returning to much fuel, or a lack of fuel volume under load.

I was told the 120 pump should be able to fuel these nozzles all day long with out breaking a sweat.

Yeah I was thinking at first my FASS wasn't keeping up then I did some more logging and as the engine heats up it gets worse and that is signs of an injector is returning too much fuel. I will be doing a return test this weekend. They are original injectors with 150K miles on them so I am guessing it is finally time for injectors if so 150% here I come.

[2007 5.9]

Who's CP3??

Don't say T&C....

[WisconsinHick1]

Who's CP3??

Don't say T&C....

No sir it is one of John's pumps.