When I run about 2300 RPM in my 2000, the engine feels like it's starting to stumble. It only does this in 4th gear. I think that may be due to the engine loading in that gear. I can run WOT in 5th and there is no stumble, but I haven't tried to run it at 2300 RPM in that gear (way too fast). Could this be a sign of the lift pump going out?

 

It is a possibility do you have guages in truck if not you may have schrader valve on the vp44 there will be a cap on the driverside you can remove get yourself a guage something that reads 0-20psi some diesel fuel hose about 7 feet and a shraeder valve you can pick these up at refrigeration repair house's.

 

No gauges, I'll try to locate a pressure guage and check it.

 

Checked the pressure, it was 0 PSI. It hasen't done it since that first time. BTW I changed out the lift pump.