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Had a talk with an old Mack guy that changed how I look at injectors
Been working on a 2001 Cummins ISX for a dude at the shop, chasing a miss that just would not go away. Swapped injectors twice, checked the lift pump pressure, even replaced the ECM connector harness. Then this guy Dave, retired fleet mechanic from the 80s, comes by to pick up his truck and sees me scratching my head. He just says 'bet you haven't checked the rocker arm geometry for a wiped cam lobe yet.' I blew it off at first but after 2 hours of checking everything else I pulled the valve cover again and sure enough one lobe was worn down maybe 0.020 inches. Never even crossed my mind on a newer common rail setup. Has anyone else had hidden cam wear fool them on a misfire?
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elizabeth9001mo ago
You ever spend hours chasing a ghost like that? Same thing happened to me on a 2011 ISX last spring. Missed like crazy at idle but cleared up on the highway, swapped injectors, sensors, even did a compression test. Finally pulled the overhead and found a cam lobe that looked like a worn down lollipop. Thing barely had 400k on it too. Makes you wonder how many guys are out there replacing injectors on engines that just need a cam and some rockers.
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loganthompson1mo ago
Elizabeth900 that's a rough one. 400k on a cam going bad like that is wild, sounds like a bad batch of steel or something from the factory. Been there chasing a miss on a 08' DT466, swapped all six injectors, spent a full weekend pulling my hair out. Turned out the injection pump was just barely out of time, but man, the feeling when you finally find it is a mix of relief and anger at all the parts you wasted. Makes you want to tear the whole thing down before throwing parts at it next time.
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valh3221d agoTop Commenter
Blew a water pump on my old F-250 last year, spent two days cussing at it before realizing the fan clutch was locked up tight, had been putting stress on everything for who knows how long. Made me wanna pull the whole front end off just to inspect every damn part (which I basically did, ha).
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