98 454 lean and fuel pressure

[ailver79]

Recently purchased the truck. Shows 133,*** on the odometer. Got truck with a K&N filter and a straight through 4" muffler. Still has cats. In the process of replacing leaking intake gaskets and repairing a hard hot starting issue, I did a new fuel pressure regulator, 5.0 motorsports "stock improvement injectors," cap, rotor, upstream 02's and fuel filter. Put 100 miles on it today and got CEL for lean on both banks. Pulled up fuel trims and went for a drive, both long terms at at 25. Checked for vacuum leaks, cant find any with ear or carb spray. Checked fuel pressure Key on engine off, cycled 5 or 6 times got 52 psi. Running pressure is 45 with a spike up to 50 when I whack the throttle, no load. Pinched off the return line briefly and had no change in psi. Pump has always been loud. Plan is to check engine with a vacuum gauge tommorow, voltage and ground at pump harness, inspect pump connectors if I can get to them, and see if I can get the low amp probe from my scope on the harness without dropping the tank. Truck starts fine when hot or cold, seems little low on power as compared to before. My thoughts are, Old injectors were sticking open, made good power with a weak pump because of that. New injectors want more fuel than the old pump can provide whether that be mechanical or electrical. Probably only put 100 miles on the truck before starting the surgery, so don't have much baseline. Am I missing something?

 

[454cid]

When i clamped my return line the pressure shot up to about 90psi immediately.

 

[GM Guy]

make sure purge solenoid is working and you arent developing alot of vacuum in the fuel tank, that would make the pump work harder.

 

[ailver79]

Thanks. Purge solenoid shows full duty cycle under load on scan tool. I'll command it off and on tomorrow. Just went back through it tonight. Clamped off return hose again, running pressure stays at 45. I then deadheaded the gauge at the new filter and cycled the key about 6 times, gauge got to 60, but dropped fast. Checked for power and ground at pump connector, connections looked solid and tested 13.0V running on both sides. Jumpered fp ground at frame and thermostat housing and stayed the same. I'm calling it a bad pump and going to decide which one to get. Thanks for the help along the way.

 

[454cid]

make sure purge solenoid is working and you arent developing alot of vacuum in the fuel tank, that would make the pump work harder.

Edit: Oops, I thought this was my thread..... I've got an evap issue, too.