fuel line pressure bleeding off -what is suppose to maintain the pressure?

[sehaare]

Hi guys,

98 4wd v6 SOHC Auto

I did a little troubleshooting on the car and it appears that the fuel line pressure is bleeding off if the car sits for a while (rough start after a matter of hours. no start after a matter of days).

From going through the treads I found the trick of cycling the key on and off before starting to get the fuel pump to get the pressure back up. I've done this and it has worked every time.

I've found bits a pieces of info on the system in multiple threads but I figured there had to be a fuel system guru out their that could put it all together for me.

What is supposed to maintain the fuel system pressure when the engine is off and what are the likely causes of failure?

I want to have my ducks in a row before I go though the pain of pulling the tank to figure this out.

Thanks
Steve

 

[rileyrs]

the system is essentially always under pressure, simply because the pressure doesnt leak out anywhere when its off, but when you turn on the battery, you hear the fuel pump prime, to ensure pressure in the system, and to start to pump, so its ready to supply fuel while the truck is running,
it sounds like you might have a leak somewhere in the fuel system that makes it lose pressure over time, or maybe just a weak fuel pump

 

[sehaare]

Thanks for the reply

I know that in other systems that I have worked on there was a check valve to prevent the fuel from leaking back past the pump into the tank. Others have had fuel accumulators that use a diaphragm to keep pressure on the system.

Granted these have been fuel systems that were much older than my 98, but I would think that the system would at least have to have a check valve or what would keep the fuel from flowing back past the pump impellor and back into the tank?

 

[Turdle]

I think there is some confusion in this subject.

I know, for a fact, the pressure on my 98 v8 would bleed down with all stock components ( injectors-rails lines pump regulator etc) and does so with aftermarket ones also. I wonder if the return style fuel pressure regulator dumps off -as my aeromotive regulator does.

 

[Cobraguy]

Jon, it shouldn't bleed off below the regulator setting. But in realty, they do. Still it should hold a fair amount of pressure in the system...returnless or return. If not, you have a check valve, regulator, or injector leaking.