Talked to an old fleet mechanic yesterday and he flipped my whole approach on injectors

I was at the parts counter at Cummins in Nashville and this guy in his 60s overheard me fussing about a bad injector on a 6.7. He said I should scuff the bore with a 400 grit before seating the new one. I always just cleaned and dropped them in. Tried it on the job this morning and the engine smoothed out way faster than usual. Has anyone else heard of doing this or was he just yanking my chain?

3 comments

3 Comments

wade8711mo ago

Yeah I used to think scuffing a bore was crazy too. Always figured clean and drop was the right way, like putting in a new spark plug. But a guy I trust tried it on a 6.0 powerstroke last year and swore by it. Now I do a quick pass with some 320 grit on any injector that's been in there a while. Takes an extra minute but the idle is way smoother from the get go. No more waiting for it to "break in" for a hundred miles.

simonp761mo ago

You sure it's not just in your head? Hundred miles of break in doesn't sound like a big deal either way.

lindag331mo ago

Wait, so now we're supposed to sandpaper our injector holes like we're refinishing a coffee table? I've been wrenching for fifteen years and never once thought "you know what this precision machined bore needs, some grit." Sounds like that old timer was trying to get you to ruin a thousand dollar injector so he could laugh about it over a beer. But then Wade here says it works, so now I'm questioning my whole life choices. Next thing you know some guy at the parts counter is gonna tell me to spit on my glow plugs before installing them. I swear, the diesel community is full of voodoo magic and luck charms.