1998 Chevy Suburban

yes. have a fuel pressure drop test done again.

well i have a snapon solus scaner and ran a test with it all the injectors would drop the pressure from 50psi down to 20psi

you need to pressurize the system and see if the pressure holds. if it does then nothing is leaking. i think your going to find that something is leaking, like possibly a cracked fuel line inside the intake or faulty o ring. get back to us

well the engine is a 7.4 and when i had the upper intake off after replacing the regulator i pressurerized the rail and looked for leaks none should i take the rail out hook up the fuel lines and pressurerise the the rail .when the engine is off pressure and the pump cycles psi will hold for about 20 min then drop then after about an hour it will be down to 20 psi

if it holds that long then dont look for the leak. if it was that then the pressure would drop off quick. i just looked up fuel pressure and im coming up with the lowest fuel pressure should be 56 psi. what do you have .

you have a mass air flow sensor. correct? try cleaning that. also how does it run? consuming oil?

key on psi goes up to 60 when pump quits drops to 51 cleaned maf because i was getting code for that awhile back as far as oil one qt between changes 3000mi it runs great way back it was getting codes for low voltage to o2 now those are gone still have the rich codes and the egr1404 and those are the only ones that keep coming back before new regulator psi was low 34psi

at this oint we need to watch o2 voltages on a scan tool and read other values. not much more we can do here but pitch parts. let us know how you make out.

well i think it might have bad injectors what else could give it rich codes some times it holds pressure over night like 45psi then some times it drops down to 20psi in a hour

these injectors are pieces of junk. replace the whole set with the new style injectors.