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TIL a 12-valve Cummins can still surprise you with a weird failure
Had a 1994 Dodge with the 5.9L in the shop yesterday for a rough idle. Traced it all the way back to a cracked injection pump mounting flange, which I've never seen before on that engine. The owner drove it from Boise thinking it was just a fuel filter. Anyone else run into something like that on the old mechanical pumps?
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sandrap406mo ago
You know, it makes me wonder about the trucks that sat for a long time. My uncle had one that was a farm truck, barely driven for years, then started daily use. The constant heat and cold cycles from sitting then running might make that metal MORE brittle than one that's been driven steady. It's like how an old rubber band snaps when you finally stretch it.
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burns.grace7mo ago
Read a forum post years ago about a guy with a similar issue, but his was from the pump itself working loose over time. Those old mounting flanges can get brittle with age and heat cycles, especially if someone overtightened the bolts during a past repair. Makes sense it would cause a rough idle with an air leak in the fuel system like that. Surprised it made it all the way from Boise before it got really bad. Always something new with those trucks, even on a motor you think you know inside and out.
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charlie_jenkins7mo ago
Spot on about those old flanges, @burns.grace. It reminds me of how so many problems come from things just slowly working themselves loose, you know? Like a wobbly ceiling fan from one screw backing out over years, or a dripping faucet from a washer that just gave up. We fix the big, loud breaks, but the quiet, slow shakes from age and wear, those are the ones that really sneak up on you.
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