fuel filter?

[kdog]

I put a 6.0 Lq4 in my 1990 chevy K 2500. I replaced the fuel pump with a Master E3270.

My engine is running lean. (first it was just the left bank P0174, but now is showing on both sides)

The guys at Tunex were not able to find any air leaks in intake or exhaust. They think the problem is in the fuel delivery. They say injectors check out ok.

My fuel pressure is generally around 55 psi but the PSI will jump around a lot. ( I understand that fuel should be from 55 to 62 psi, correct if wrong.) Problem is I can't remember if I replaced the fuel filter or not. I did replace some fuel lines so I may have done the filter but I don't know. Also is the fuel filter for the tbi350 different enough from the filter on the 2004 6.0 to warrant a problem there?

Do the symptoms, fuel psi jumping around indicate the filter? or did I put in the wrong pump?

Thanks for all your help.

As for how the truck is running now it seems to be overcompensating for the lean code and running rich enough to heat up the exhaust super hot.

[RedHeartbeat]

A common error that occurs when replacing the fuel pump it to reuse the original hose that joins the pump to the steel line. The hose isn't strong enough and will rupture and cause fuel pressure issues. I'm not sure what you used to join the pump to the line but that's very common. A good steel braided hose that is rated for about 70PSI or better would be highly recommended. Another issue can be the filter element in the fuel filter. The stock unit isn't intended for 60 PSI of pressure and could collapse internally. A replacement filter from a 95-98 truck would be advisable if they have the same fittings, not sure if they do or not. WIX filters usually have a metal support on the filter media that others don't. That will help prevent collapsing the element if you have to go to a stock replacement filter for your model truck.

[kdog]

It turns out now that my memory serves me correctly that replaced the filter with a corvette filter and did replace the rubber hoses.

Is there anything else I should be checking?

Thanks

[RedHeartbeat]

Power supply to the pump would be my next thing to check. Look for corrosion on the terminals or relay. Put a voltmeter on the power wire as close to the pump as possible and watch for voltage fluctuations over time. You may need to put a fuel pump hotwire kit in or just may need to replace a corroded connection.

[kdog]

Thanks for the response. My fuel pressure is around 55-56 and sometimes drops to 49 or so. the guys at tunex are thinking maybe the problem is not in the fuel system and come to find out they accually have not checked the injectors as they said "checking the injectors is a pain". Anything else you might steer me towards? or should I just let them keep checking stuff untill they (Hopefully) find something?

[RedHeartbeat]

You could have a pump that's about to fail, also. Be sure you have at least 1/2 tank of fuel to keep the pump cool and then put a test jumper to the pump. I'd run a jumper straight to the power lead on the pump from the battery and monitor the fuel pressure. It should be consistant. If it's not then you must find out why. Your test should involve the connections and the wires themselves. Run a length of wire to the connection at the tank and test there, also. It will have to be a good size wire to run that distance or be silver instead of copper to keep from losing voltage over the distance.

[RedHeartbeat]

Oh yeah, check your grounds from the pump to the chassis.

[kdog]

The pump was installed new a few months ago. Is there something that is causing it to fail or am I looking at the possibility of a bad pump to start.

Also sorry for the missinformation. It looks like it stays constant at 55 psi except for one drop right after startup.

Should I be concerned that I am not at 58 psi?

Thanks

[RedHeartbeat]

Depends on the accuracy of the gauge. Most aren't exact. If you can, compare your readings to those on another truck similar to yours. Does you fuel rail have a vacuum referenced fuel pressure regulator on it?

[kdog]

It does have a regulator on it. I spoke with a programmer since my long term fuel trims are at 16% at idle and 20% for the rest of the rpm band. He suggested that by bumping up the psi to 58 or maybe even higher that this would bring the fuel trims down. There still may be a programming issue on top of that but I was advised to do this step first.

What would you recommend?