Just installed fuel pressure gauge and as soon as you turn the truck off fuel pressure falls to 0 slowly. When you first turn the key on it goes to 9psi and then slowly back to 0 is there no check valve in the supply system of a common rail. 2006 5.9 truck.

 

I'm not sure if I'm reading it correctly but yes the pressure will bleed off. I'm not sure how fast it will bleed off but this sounds normal to me. Are you having and running issues or this is just something you noticed but all is still normal?

 

Every thing seems fine just bought the truck new to commonrails. Thanks

 

Yes, that is completely normal for the ECM controlled fuel pump.
9 psi pressure with the pump running, engine off is normal but not really usefull. Watch your fuel pump pressures with the engine under load.

Sometimes when you turn the key on, the lift pump will not run. Also normal.
To force the pump to run everytime without the engine running, just bump the key, crank the engine for a split second, with the ignition key.

 

When you turn the key on the lift pump will run for about 2 seconds. If you bump the starter but do not start it will run for about 25 seconds.