project: watch out Kentuckians

[Macrobb]

when I start the truck in the morning it stays at 5-6 psi. after a little driving it slowly starts to go lower and lower, and after diving on the highway it will read maybe 1 psi. I did put on a new lift pump but not sure if it might be something else. it has never run out of fuel or began to starve of fuel. I just don't want to have an issue on a long drive.

It may just be a matter of thinner fuel when hot, and more fuel going out the return. Quite a bit goes out the IP return line, getting pulled through it by the vane pump in the IP.

As long as it stays positive, you should be fine - especially at higher RPMs, the IP will pull whatever fuel it needs, and quite a bit of that ends up going out the return.
If you do get negative pressure... check the fuel pump, filter, and possibly the fuel pickups.
If you do get a partial clog(and restricted fuel, without air), you'll notice a lack of power but no stumbling. Also no smoke. Just like you have your pedal at 1/4 throttle instead of floored.
It's only when you start sucking air in that you get stumbling.

I'd measure underhood temp, put any slow-reacting thermometer under and drive it around.

Why not go with a simple thermometer, one of those cheap digital ones with a 5' cord to the sensor. Just run the cord out the window(or through the door seal) and under the hood.

 

[no mufflers]

It doesn't seem to run out of fuel. I can always get full boost so I have fuel. I just wasn't sure if that was normal.

 

[laserjock]

What kind of gauge are you running? Remember my debacle with the fluid filled gauge?

 

[no mufflers]

What kind of gauge are you running? Remember my debacle with the fluid filled gauge?

yes, I have been thinking about that. its a redhorse liquid filled gauge. it seems to be doing better but haven't tried cooling it yet.