took my car out for a drive today at idle the fuel pressure was 42.5 on( factory regulator) and when i gassed it (wot) i saw no knock on the scanmaster. drove for about 30 miles.. when i restarted it to go home fuel pressure was only at 36 lbs at idle and when i punch it (wot) it startes pulling timing right away i also have the btm turned up to 3 so it's already pulling maximum timing. where did my fuel pressure go? is it starting to knock more because it was at maximum temp? any help would be appreciated thanks

 

well thought this was weird also. unhooked battery for night and pulled gas cap off. when i rehooked everything in the morning and restarted it fuel pressure was back at 42.5 again maybe the tank in seeing to much pressure? any way i have a lt4 km and have been monitoring knock before and always and have never seen any i'm still dumbfounded.

 

When you punched it did you notice if the fuel pressure went up? Are you running an FMU?

 

yes i am running an fmu my pressure rises proportional to my boost 85 max. i drove the car normal again today when i started out it ran flawless no knock retard smooth throthle response again after it heated up it started pulling knock like crazy.and again my fuel idle pressure went down to bout 37 at idle. so when i got home i disconnected the battery again and the fuel cap then took it out for a another ride and it ran flwless again no knock!! i know from monitoring the computer that sometimes it throws a egr code and ses light then goes away and the blm 's go to 108? means it's running rich so it's pulling fuel. i thought maybe a stuck injector but they all ohm out the same please help

oh and i put brand new o2 sensors in this morning and still having same probs

 

With 85 PSI of fuel pressure arnt you in the running for locking up the Injectors?

 

Next time it gets hot and the FP drops, open the gas cap and see if you have a bunch of pressure in the tank. It may just be time for a new gas cap.

 

thought the gas tank was a closed system supposed to be pressurized it has some serious pressure in it i can hear it hissing