Just spent 4 hours chasing a ghost in a Cummins ISX fuel system

I had a 2018 Peterbilt with a random stumble under load, and it ended up being a tiny piece of rubber from a cheap fuel line that was floating around in the return side. Took me swapping the filters three times and finally pulling the banjo bolts to find it hiding in the check valve. Has anyone else dealt with contamination that acted like a electrical gremlin?

3 comments

3 Comments

ellis.rose27d ago

Paint strainer trick is genius, definitely stealing that one.

gonzalez.vera27d ago

Had a 2013 T680 that did the exact same dance. The rubber particles are sneaky because they're just soft enough to get past the filter on a cold start but swell up when the fuel warms and block the return. I finally got smart and started using a clean paint strainer between the tank and transfer pump on any fuel system diagnosis. Also check the tank pickup tube screens if you've got them. Those little accordion style ones on some Cummins trucks will catch debris but also starve the pump if they get hairline cracks and suck air.

hugo_craig27d ago

Had a Ford 6.0 do something similar once. Stumble at highway speeds, no codes, everything looked clean. Turned out a mouse had stuffed some insulation down into the fuel tank vent line. Would get sucked in on a long hill, block the tank vent, and the pump would start pulling vacuum. Let off the throttle and it would unstick and run fine. Drove me nuts for a week. Finally found it when I was checking vent lines with compressed air and heard something pop loose inside the tank.