Old timer at a truck stop taught me more about diagnostics in 5 minutes than my whole first year

I was stuck on a 2015 Cummins ISX at a Pilot in Billings, Montana last month. This truck had a rough idle that just would not clear no matter what I did with the injectors. This retired mechanic in his 70s walks over, sees me scratching my head, and says 'check your crankcase pressure first before you touch anything else.' He was right, it was a stuck ring on cylinder 4 the whole time. That one tip has saved me about 6 hours of chasing ghosts since then. Anyone else run into an old school guy who dropped a knowledge bomb on you like that?

2 comments

2 Comments

sullivan.spencer20d ago

Did he have a handlebar mustache and a hat that looked older than his truck? Honestly, those old school guys have forgotten more than most of us will ever learn. I remember my first year I spent two days chasing a misfire on an old Detroit Diesel, and an old timer just walked up, tapped the air filter, and said 'it's plugged, dumb kid.' Was he wrong? Nope. Ngl, I still feel like a total rookie every time I watch someone who actually knows what they're doing. It's humbling but also the best way to learn.

ryan36920d ago

My first year at a shop in Tulsa, an old-timer named Ray showed me how to check for a bad injector by cracking the line nuts one at a time with the engine running. That trick alone saved me from pulling the valve cover on a dead cylinder more times than I can count. Those dudes have a way of cutting straight to the root cause without all the guesswork.