motor is off, I've had different results...sometimes the fuel pressure holds forever...one test it dropped to 24 psi within 20 minutes...then last night I started her up...got the correct FP reading...then this morning the FP was at zero! (but the thing is with zero FP this morning she started up like a champ cold versus the horrible warm/hot starts that I have to press the gas to get her going...even with fuel pressure reading perfect)....so trying to figure out if this is a bad Fuel Pressure Regulator?...or the check valve that you're referring to or what?