83 12v Cummins swap sputtering under load

[NewMexCrew]

HELP!! I currently have a 1990 GMC Crew Cab with an 83 12v Cummins in it. I am new to the Cummins engines. Recently the truck started sputtering under load like if it is starving for fuel. Truck starts fine and runs fine around town but while towing or going up hill at highway speeds under load it starts to sputter like its running out of fuel. If I back off the throttle it gets a little better. Any ideas on what could be wrong? Could it be the lift pump? I recently changed the fuel filter and air cleaner. Any help would be greatly appreciated.

[NewMexCrew]

Anybody?? If this is the wrong location for this please let me know.

[usetheBFH]

Could Definitely be the lift pump. I HIGHLY recommend getting an in-cab fuel pressure gauge. That way you can watch the line pressure. I have had about a half dozen lift pump failures on 12v engines. you may have 20-30 PSI at idle but under throttle it will have 0 PSI.

If you don't have a gauge you need to get one.

[NewMexCrew]

Thanks usetheBFH. How hard is it to install a fuel pressure gauge?

[COS399]

On my 88 R30 the rubber hose inside my fuel tank had not been removed and the rubber turned to mush and was restricting the flow. I removed the rubber line and everything below it and then extended the line down with a copper line and compression fitting. Hope you find the problem soon and good luck.

Keep us posted on your progress.

[NewMexCrew]

Thanks COS399. If weather permits I'll take a look at that this weekend. I might also just replace the lift pump and put the piston style lift pump right away. I will keep you guys posted.

[NewMexCrew]

Meant title to read 93 12v Cummins swap sputtering under load