I have a 98 Firebird 3.8L. I checked fuel pressure key on not running and it is 44 psi. With engine running and vacuum line disconnected it is 52 psi. Is this adequate? I have a P0301 ses code and replaced plugs wires coil pack icm and switched injector. The plug from cyl 1 was clean.

 

Looked it up in my '01 helms and for the 3.8, commanding the fuel pump on with a scan tool, ignition on -car off should be 48-54 psi. Also says to command it on a few times to get the highest reading. Doesn't sound like a fuel pump issue, something else is going on.

 

My Haynes manual also says 48 - 55 psi key on not running. I am only getting 44psi. Engine running and vacuum line disconnected it is 52 psi. If pressure is adequate could flow rate be inadequate?