I have a 2008 f250 with a 5.4 high miles around 300,000, with a cold start it runs like it’s brand new. Then around 10 mins of idle the short term fuel trim goes up to like 59%, then fuel pressure drops to about 5% until it dies. Code comes up is fuel rail pressure sensor of course. I started by replacing the sensor, then fuel pump driver, fuel pump, fuel filter, all fuel injectors, throttle body, mass airflow sensor, all O2 sensors vapor canister purge valve. Then did a smoke test on the vacuum lines with no leaks, intake tubes same.

Any help would be awesome!

thanks

 

You must have a decent scan tool to provide fuel trim, so can you post all the data stream info so we can see what is going on, thanks.

 

I thought stored it but apparently not. I’ll have to run it again.

I can say all the O2 numbers were in range, short term fuel trim starts around -10-12% until it warms then rises to a solid 59%. But I’ll see if I can run it again and post it.

thanks

 

Does your scan tool provide fuel pressure desired and fuel pressure actual ?

 

No, but it should be in the 40 psi range from what I read, and it’s about there until it warms up then it drops to like 5 psi. I’ve watched it live and the short term fuel trim goes up, then the fuel pressure goes down shortly after.