Fuel Pressure Questions

[myersnate]

I am having some issues with my 2001 GMC Sierra 2500HD with the 8.1L Vortex gas engine. After sitting for a long period of time or first thing in the morning the truck will not fire on the first attempt. It ussually takes 2-3 three turns of the ignition (cycling of fuel pump) before the engine fires. So I replaced the fuel filter, plugs and pressure regulator. Hopeing one of these cheaper fixes would work. I also connected a fuel pressure gage to the fuel rail to monitor the pressures. Here is what the fuel pressue does:

 

 

• Turn ignition to cycle fuel pump only - no pressure is at the fuel rail
  
• Turn key off and then back on to cylce fuel pump - pressure builds to 60 psi then reduces immediately to 50 psi then begins to slowly reduce until it reaches about 4 psi (just above zero on the gage)
  
• Turn key off then back on to start fuel pump and crank engine - engine fires with no issue
  

So what I am curious about is should the fuel pressure drop from 60 to 50 psi then slowly to 4 psi if the I don't try to fire the engine? Any ideas on what kind of problem I am facing? Thank for any help or advice.

[markw8]

If it starts to drop immediatly, the check valve in the pump is bad. It should hold pressure for an hour or more, then start to drop.

 

Mark

[myersnate]

If it starts to drop immediatly, the check valve in the pump is bad. It should hold pressure for an hour or more, then start to drop.

 

Mark

 

Thanks for the help Mark.

 

Has anyone attempted to just install an external check valve inline with the fuel filter instead of replacing the entire fuel pump assembly?

 

My fuel pressure during WOT is 50 psi, is this within the specified range? I am just curious if my pump is going bad which may convince me to just replace the fuel pump.