Got a buddy that got a 6.0 about a year ago. He has GH tunes, Ford blue spring kit, 4in exhaust, and all was well and the thing runs great. Last summer he buys a camper in OK and pulls it back to NM. While on I40, on a not so steep hill with a head wind, he drops speed quick. Couldn't hang with semis and he also only got about 8mpg towing this little 5k lb camper. He said it seemed gutless and real low on power. My first thought was that it wasn't getting fuel. He sees 30psi of boost. He finally got around to putting a guage on it and at KOEO it builds 58psi. Same at idle. WOT it dips to 45-47, then on a shift it drops to 35 and builds back to 52 slowly. It runs well unloaded. I haven't ridden with him while towing. I've got a 7.3 and have never been around a well running 6.0. This doesn't seem normal, though. Weak fuel pump? Clogged tank screens? Or is this normal? He only gets 14mpg also cruising at 70-75. Figured I would ask here. Thanks

 

Good that he is watching fuel pressure. Doing much driving with pressures below 45 psig will damage injectors. It is definitely not normal.

The issue could be those possibilities that you mentioned (weak pump or clogged pick-up tube screen). It could also be some other issues:
1. Does he have a chassis can 6.0L? If so, the fuel tank liner could be sloughing off.
2. Has he recently changed fuel filters (both of them)? If so, the primary fuel filter might have a leak and be sucking air in. A leaking WIF plug might also be allowing air into the fuel. If he hasn't changed filters in a while, they could be dirty
3. One of the fuel lines could be kinked and restricting fuel flow.
4. The fuel tank level might be low and the pick-up tube might be cracked or have a broken "vacuum relief valve".
5. Could the fuel have excessive water in it?
5. Even the Ford blue spring might have an issue. That has sometimes happened (although most of the times it was an installation error).

 

Thanks for this info. He took it to a couple shops before finally listening to me and getting a guage on it. 1st shop told him he had an aftermarket turbo and it was bad. Quoted him $4k to fix. It's a stock turbo and it's fine. 2nd shop told him the fuel pressure was a little low, but my BIL who works there couldn't remember the number. So he finally put his own guage on it.
1. It is not a Cab and chassis. 2006 F250 CCSB.
2. Both fuel filters have been changed recently. The WIF plug is peaking my interest. We will check that tomorrow. I will check that and ensure the primary filter is tight. Primary is up top correct? Please excuse my ignorance on these.
3. I dont think this is the issue, but will check. Where could they possibly kink? Fuel bowl connections are good. We just redid the blue spring tonight. I thought it could be a bad FPR so we rebuilt it with a Ford part. One thing that was unexpected was the fuel bowl would not accept the plastic piece that the brass puppet goes in. The bowl has that machined into it. He previously used and XDP no name kit. The Ford spring is noticeable stiffer and thicker, but this kit did not change anything.
4. Full tank of fuel, just filled this morning. It may come to dropping the tank but that will be another day when he can come to the house. We are fiddling with it during downtime at work.
5. I dont think it's the fuel. This has been on going thru multiple tanks. Will opening the WIF plug rule this out?
6. I also can rule out the kit having issue as nothing changed from the old kit to the new.

 

The primary fuel filter (and pump) are all part of the HFCM by the driver's side frame rail (under the truck). The pump pulls the fuel from the tank, so it is potentially under vacuum until it exits the pump. That is why it can pull in air from a poorly installed filter cap or the WIF plug. The fuel is under pressure at the secondary fuel filter (in the engine compartment).

If any of the fuel lines have been disconnected at the secondary fuel filter (or at the regulator), they could have been kinked if a back-up wrench was not used. A visual inspection should answer that question. I suppose fuel lines could be kinked/dented in other places. but the lines at the regulator are the most common ones.

Yes, draining fuel from the WIF plug would be a way to check the fuel quality.

Sometimes people use a fuel additive and they accidentally let the metal seal on the bottle get dropped into the tank. This can blind off the pick-up tube screen. Maybe a borescope could show something, but it may require emptying the tank. Hopefully he is confident that he hasn't let anything "foreign" like that into the tank.

If none of the above, then I would suppose that the pump was weak. That is how mine behaved when it failed.