ISX SPN 94 FMI 18. Low Fuel Pressure

Back story. I purchased the truck in 2015. That summer I would regularly get the same code. Always loaded heavy, running in high altitude mountain areas, and after several hours of daytime (ie: HOT) running. If I was running east across Wyoming during the day I pretty much knew about 10 miles from Laramie I'd get the engine warning. Engine would idle rough. I'd park for a break and truck would be fine.

Fall and winter came and never had any issues again. Even running the southwest last summer pulling copper up a 5 mile 9% grade, no issues at all.

Yesterday rolling across Wyoming. Temp in the 30's.. engine warning, truck shuts down. Got it restarted by by simply clutching for a few seconds. Pulled over, idled very rough very much like after a filter change. Today, Oregon Mid 50's, climbing a 6% grade, halfway up, warning light, engine shuts down. Restarted immediately and ran smooth. SPN 94 FMI 18, 2 occurrences.

KO/EO the lift pump sounds like its struggling, changing tone and speed.

I'm guessing the lift pump is on its last legs but I'm open to suggestions. I plan on checking condition of the wiring and plugs at the same time I change the pump.

 

I'll give a good inspection to the lines but my gut and experience with electric pumps is leading me toward either a failing pump or power failure. Since its never had any issues unless heatsoak was a possibility I'm leaning heavily toward the pump. Today it has run perfect... of course not much chance of heatsoak while running through snow in the northern Cascades.

 

Problem solved. Pressure tested the fuel system then put a vacuum on it just to be sure. Passed both tests.

The lift pump failed hard. Unstable pressure readings jumping between 8 and 15 psi when KOEO.

Replaced the pump and holds a steady 15.2 psi.

Thanks for the replys!