There is no check valve in your system to hold pressure once the engine has stopped running. What actually allows pressure to build up in the system is the overflow valve on the return outlet of the injection pump. The overflow valve has a ball valve in it to control housing pressure of the VP44. This valve also has a small orifice in it that bypasses the ball valve to allow air to escape and to cool the injection pump. The will prevent the system from holding pressure.

I suspect your have either air in the system due to the poor running at 5 psi. Unless you are towing or have a load on the engine most people don't notice there lift pump is not running until the injection pump fails.

 

could you walk me through the steps to bleed air from the fuel system?

 

so your having hard starts or the fuel pressure just drops out while driving?

 

it wont start now, the only time it has fuel pressure is when the fuel pump is running. when the pump kicks off the fuel pressure gradually falls away, thats what was making me think there may be a valve of some kind stuck open? but how do I bleed the air from the system

 

the only time it has fuel pressure is when the fuel pump is running. when the pump kicks off the fuel pressure gradually falls away,

Thats how it works.

 

I thought before I could cycle the LP and it would hold pressure until I started the truck

 

most likely your connector tube o-rings are leaking and that is whats causing the hard starts, the fuel pressure thing is normal

 

it wont start :confused013:

 

crack 1,3,4 lines at the head and have somebody turn then engine over, when it starts pumping fuel out of the lines then close them, it should start, if your by yourself then just put a shot of ether in the aifilter housing and start the truck.