1996 k2500 5.7 fuel pressure is 60psi with key on engine off when it is idleing it drops down to 50psi and after i turn it off it will drop to 0psi. reason i checked fuel pressure is truck is low on power all across the rev range. is there anyway to tell if it is fuel injectors vs fuel regulator or maybe the fuel pump? ive searched for weeks and read so many forum posts and i have yet to find any help on this subject any help would be amazing
60psi KOEO is within spec for a 1998 (60-66psi), I assume 1996 is the same.
Fuel pressure should drop with the engine running at idle. 10psi sounds about right, as the drop in fuel pressure roughly follows the manifold vacuum (which, at idle, would be around -10psi relative to atmospheric).
The fuel pressure drop to 0psi shortly after turn-off may indicate a leak, which, if leaking into the intake, would cause the O2 sensor(s) to instruct the ECU to reduce the fuel delivery; if so, the long-term fuel trim(s) would be inappropriately affected and driveability likely suffer.
Others will I'm sure have better comments than mine.
Have you checked the ECM for codes? Do so even if the CEL is off.
Intake gasket leaks are common on the L31. Is it using any antifreeze? Is there any evidence of contamination in the antifreeze? Is there any reason to believe air is leaking into the intake tract downstream from the MAF sensor?
Can you attach a scan tool and check the long-term fuel trim values?
There are ways to check the injectors, e.g., using a Tech2 to run the Fuel Injector Balance Test and the Injector Coil Test (see attached). These instructions are given in the 1998 factory service manual and I assume are relevant to your year.
There are other sensors worth checking too, e.g., MAF, TPS, to name but two. Let's see what others say.
