Ok so here's a brain teaser for Thanksgiving day see what you can come up with.

99 K2500 Vortec 7400

I started with low fuel pressure and so far have done the fuel pump, fuel filter and fuel pressure regulator. The injectors were already done when I purchased the truck. The pump is a delphi and reguator a BWD, when I did the regulator I verified that the injectors were not leaking.

So with engine off key on it jumps to 62psi but as soon as the pump quits it drops immediately to nothing, crimping the return line makes no difference.

Engine on pressure hold steady as a rock at 49 psi and jumps to around 56-57 psi for a second then levels back out at 49, once againg crimping the return make no change.

I have been over it multiple times looking for leaks and don't see anything at all, I am completely at a loss as to what needs to be done next anyone ever seen anything like this or have any ideas of what to try now? I have a group of guys expecting this truck to take them from GA to AR on a duck hunt and I hate to let someone down.

 

Key On Engine Running(KOER) pressure should be lower than, Key On ENgine Off(KOEO), the cauum referenced fuel pressure regulator bring sthe fuel pressure down when vacuum is applied.

If you are complaining about your dropping fuel pressure and since crimping teh return line makes no difference you either have a leaking fuel pressure regulator, or leaking fuel injectors or fuel pressure is leaking back through the fuel pump.

I dont understand why while idling your ful pressure spikes up to 57-58psi then back down to 49psi??

peace
Hog

 

You Could have Low volts do you have a intank pump or EX?