LB7 Rail Pressure Issue

[Ne-max]

I am helping a buddy with his truck. It was having shifting issues in the higher gears. Truck runs good and don't smoke. He just has to get up in the rpms for it to shift. I hooked up my laptop and cleared all the codes. Then went out on a drive to data log it. After logging it I noticed that the Commanded rail pressure would get up to around 23000 but the actual rail pressure would stay around to 5-6000 psi. It is throwing the P1093 & P1094 codes. Its just odd cause the truck seems to run pretty good and don't smoke. It starts real easy. Truck has 340000 miles but unsure of the history. It almost seems like a cp3/FPR issue to me but wouldn't it run like crap with that low of pressure? Could it just be a rail sensor?

 

[Ne-max]

Bump

 

[02greysixer]

My lb7 ran and started good with two seized plungers in the cp3. Don't know what pressures it'd build. It's surprising how well they can run with low rail pressure and just be down on power

 

[Ne-max]

Also you can't really feel the difference in his #1 tune to number 5. That's why I'm leaning towards cp3. But it should limp out with that big of differance in pressures also

 

[AKlowriderZ71]

Mine ran fine with a weak CP3, but sometimes at higher rpm and heavy throttle, it would go into limp mode. A bottle test on the injector return was okay. Added the CP3 return to the bottle test, and found the CP3 bypassing 3x allowed max spec.

A reman CP3 solved my problem. Have you bottle tested it?