Found out today that a loose injector cup can mimic a blown head gasket

I was chasing a miss on a 6.7 Powerstroke in the shop this morning, pulled the injector and noticed a tiny bit of carbon tracing around the cup. Turned out the cup was just loose, not cracked, and it was letting compression bleed by. I found a TSB from Ford that explains how the symptoms match head gasket failure exactly. Has anyone else wasted time chasing the wrong thing because of a loose cup?

3 comments

3 Comments

rowan96920d ago

Happened to me on a 2014 Ram 3500 with the 6.7 Cummins last spring. Spent three days chasing a miss that came and went with temperature, even threw a new set of injectors at it before I figured out the cup was just a hair loose. Found it by accident when I was checking torque on everything else. Ended up just cleaning it up and putting a new copper washer on it, ran fine after that. But man, that was a long weekend of cussing and swapping parts for no reason.

wyatt_mitchell2619d ago

Oh man, I've been there but in the opposite direction. I once spent an entire Saturday swapping out a perfectly good head gasket on my old 7.3 because I was so sure that's what the white smoke and overheating was. Spoiler alert: it was just a stuck thermostat and I felt like a real genius when I realized it. This job will humble you every single time, I swear.

the_simon19d ago

Did you ever figure out what caused the cup to come loose in the first place? I've heard those 6.7s can have issues with that if they've been run hard and hot a few times, but I'm curious if it was just a factory fluke. @rowan969, your story about finding it by accident is exactly why I always tell the younger guys to start with the simple stuff first and work through a checklist, even when you're sure you know what's wrong. That thermostat on your 7.3 must have felt like a real kick in the teeth though, all that labor for a ten dollar part. It's a hard lesson but it sticks with you, I know it did with me after I did something similar on a gas burner years ago.