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got a 97 C3500HD with a gen 6 MPFI 454... been going through it... been getting lean burn codes on the O2 and 1406, above 1/2 throttle engine tends to lay over on power dragging a 7k trailer and gets more noticeable the heavier I get...

cant get the fuel system lined out... new filter/fuel pump w/sock/injectors..

all data has 56-62psi for specs

key on fuel pressure 46psi

key off fuel pressure drops almost instantly to 15-20psi

free rev drops to 40psi from 46psi

all pressures measured at test port.

putting a 340LPH pump in the tank will probably mask the problem due to shear volume of fuel sent..

picked up adapter to swap line to -6 AN to run from tank to engine for supply and return incase one of the steel to hose transitions pealed over and is restricting flow..

fuel pressure regulator is vacuum controlled

both FPR and fuel pump are under 12M warranty...getting new FPR tomorrow

could I have a gotten a bad fuel pump?
upon further parts review.. fuel pump I got is rated at 35GPH and 85psi swaping it out got the 58gph/110psi version

Sounds like a bad pump. You have already shown it doesn't meet spec.

Yup, sounds like you got a bad pump.

Can't see why a 340 lph pump would be a good idea; it probably ran fine for many years with the OE one. Should run fine again with a properly working OE replacement as well. No need to step up to overkill on it.

Probably not the FPR but could be, worth a try before dropping the tank.

got the 58GPH version in, everything seams good now...
end goal is 400-450FWhp out of it.. IDK if a ~220LPH will support that or not obviously a 340LPH would have no problem

no bed on the truck right now, so pump swap is easy
got a 0411 swap about to get done as

exhaust is on.. engine still acts like its running out of fuel under a load...

anything pressure/inertia/other switches that controls the fuel pump relay that I should check?

answered my own question....

Quote:

When the ignition switch is turned to the ON position, the VCM energizes the fuel pump relay for 2 seconds allowing the fuel pump to pressurize the fuel system. If the VCM does not receive any ignition reference pulses (engine cranking or running) within 2 seconds, the VCM de-energizes the fuel pump relay. This causes the fuel pump to stop.

As a backup system to the fuel pump relay, the fuel pump can be energized by the fuel pump and engine oil pressure indicator switch. The switch has the 2 following internal circuits:

The oil pressure indicator or gage in the instrument cluster.
A normally open switch which closes when the oil pressure reaches about 28 kPa (4 psi) .

If the fuel pump relay fails, the fuel pump and engine oil pressure indicator switch runs the fuel pump. An inoperative fuel pump relay can result in long cranking times. The fuel pump and engine oil pressure indicator switch energizes the fuel pump as soon as the oil pressure reaches about 28 kPa (4 psi)

Check Fuel pressure under load. I bet it drops

You likely have a bad pump.

Got less than 50 miles on this pump..... They go bad often?

How big of a drop if any is allowed?

after multiple attempts... engine had no power... yanked the MPFI system off, put a MSD 6AL with blaster SS coil billet dis, edelbrock performer intake, fast ezi efi 1.0, oem fuel pump.. also swap to adjustable valve train with 1.7 roller tip rockers. comp cam conversion stud is #4514-16 ~$90.00 since I already did the 0411 swap ill turn all the SES codes off..

Quote:

Originally Posted by malibu795 (Post 5453460)

...oem fuel pump..

The same one that 1FastBrick suggested might be bad? What kind of hose did you use between the pump and the fitting in the tank? I would look at it first.