That Cummins ISX I swore was a fuel issue turned out to be a $35 sensor

Last month I had a 2015 Freightliner with a ISX that kept cutting out under load. I was dead set it was the CP4 pump going bad, had the whole fuel system teardown planned in my head. Turned out to be the crank position sensor glitching when it got hot, really simple swap once I actually checked the waveforms instead of guessing. Anyone else ever chase a ghost fuel problem that was just a cheap electrical part?

2 comments

2 Comments

ryanh771d agoTop Commenter

Catch yourself chasing any other unrelated electrical stuff before you found the real problem? I've had a couple trucks over the years where I swapped out the whole fuel system and it ended up being a wiring harness rubbed through somewhere dumb. Was yours throwing any codes at all before you checked the waveform or was it dead quiet until you hooked up the scope?

sage_rodriguez1d ago

Man it's wild how often the real problem is something totally unrelated. Feels like every time I go down a rabbit hole on a truck, I end up replacing a perfectly good part before finding a stupid ground wire or a chafed harness. That's just life though right? You're sure it's one thing but the universe is hiding the actual answer behind some dumb unrelated detail.