LB7 lacking power

Just posted a large thread but it didn’t seem to post...

I have two LB7’s one is a 2001 and one is a 2002. The 2001 seems to have less power than my 2002. I noticed a manifold leak and I had replaced the manifold. I’ve gained some power and you can actually hear the turbo spooling now. My 2002 LB7 pulls harder and the 2001 seems to struggle more to get up and going. Besides the manifold leaks the only other thing I’ve noticed is one of the rubber fuel lines on top of the fuel filter housing has a slight leak. If the truck sits for a week or so it has to be primed before it will start.

I’m sure there’s many other variables for this issue so I’m just reaching out for ideas. Thanks!

Welcome aboard!

First, if you have issues that have a high probability of causing power loss, chasing a power loss is pointless until all of the issues are addressed and eliminated. The fuel system is very tolerant of air leaks, but they can cause running issues, including power loss. The fuel system doesn't have a lift pump (suction from the tank to the high pressure pump), so any leak you can actually see is a large leak. Having to prime the system after a short period is a firm indicator. Most air leak conditions are not readily visible, even when the system is pressurized (by external means or an added lift pump).

That out of the way, two seemingly identical trucks rarely are really identical, especially after nearly 20 years of service. Many factors coming into play, including but not limited to, tire pressure, actual curb weight (20 years of dirt in the chassis adds up), parasitic losses (alternator, A/C compressor, etc.), intake system restrictions, overall fuel system health, electronic interference/compensation (PCM adjustments for issues not yet serious enough to trigger complaints), operating temperature (real or perceived), sensor errors (MAF, etc.), fan clutch, dragging brakes, etc. For example, something as simple and easily dismissed as a weak/failing battery can cause enough additional load on the alternator, or a weak fan clutch, fouled cooling stack or worn-out thermostats (on the more powerful truck), can cause a perceptible power loss. Also consider not all trucks sound the same, and one may simply sound faster than the other (a stretch, but a real one).