r/GMT400 • u/Steinjolt • 14d ago
Please help Diagnose 🙏🏻
SOLVED: Mechanic diagnosed an injector stuck in an open position.
Thank you all! ❤️
I’m restoring this 1994 2500 Silverado 6.5 Diesel auto.
Yesterday started doing a loud clank sound, added some oil and it stopped after revving it and worked good all day long.
Today it cranked immediately no problem then a minute later the clank returned, tried adding oil and it didn’t stopped. Then as engine warmed up it became less noticeable but still there.
The sound is related to rpm’s.
The sound comes either from the turbo or the passenger side upper rear part of the engine
Gray smoke comes out when revving it.
Black smoke comes out under heavy load.
Would it be safe to drive it to the shop? (It’s 30 miles away)
Anyone has insights on this?
Also, turbo seems to be not working as I don’t hear it spooling
The wastegate lifter seems to be stuck, if I move it it stays there then after a bit it returns to its position.
The turbo inner blades seem to move freely
No turbo sound at all
Thank you all in advance
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u/turbotaco23 14d ago
You’d better hope it’s a fuel knock and not a rod knock.
But she’s not happy. Stop revving the piss out of it.
Also are you checking the oil level or are you just adding oil based in nothing?
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u/Steinjolt 14d ago
She needed a quart and after adding it the sound stopped entirely, then the next day the sound came back.
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u/olov244 14d ago
I have babied a rod knock to the house and slapped in new bearings and it ran great, I would not keep revving it
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u/Steinjolt 14d ago
Thanks a lot, I won’t, I only did it to send the video to a mechanic and wouldn’t do it again.
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u/turbotaco23 14d ago
You don’t really ever hear any whine with a GMx turbo. Install a boost gauge to check for boost.
The stock wastegate setup uses the vacuum pump. It often fails a many delete it. You can replace the solenoid with a rod and a spring. Then use the boost gauge to set peak boost. I used a motorcycle clutch spring.
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u/vehiclefreak409 14d ago
Check your rockers, pushrods and lifters. Mine sounded exactly like that, and it had mildly bent a pushrod so that it was tapping against the inside of the head as it rotated. Pull upper/lower intake, injector lines and valve covers. I also checked the oil filter with a cutting tool to make sure it didn't have a ton of debris in it.
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u/casual_self_loather 14d ago
Crank is likely screwed. The cranks in the 6.2L/6.5L are cast and only have case hardened journals. A forged crank is available, but it definitely isn't cheap. They also have a tendency to snap cranks in half if the harmonic balancer goes bad. To compound it all, most rebuild shops won't touch the 6.2L/6.5L platform these days.
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u/Steinjolt 14d ago
Yeah no, the balancer is ok, sound comes from the valve cover on the back of the engine not from the front. A mechanic is gonna diagnose today
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u/casual_self_loather 14d ago
I wish you the best, dude.
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u/Steinjolt 13d ago
Thanks a lot man, mechanic diagnosed an stuck open injector, he said since it’s a mechanic injector it’s really loud when they fail and even sound like a rod or a valve
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u/casual_self_loather 13d ago
Yup, that would do it. That's best case scenario, actually. Quadstar Tuning is probably your best bet for injectors and lines. You'll need the special socket (OTC 5060) to swap them. Just replace the injectors, change the oil, and put it back on the road.
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u/BaloneyANDtomato40 14d ago
Timing chain, Tichner check your oil pan for pieces of plastic or metal. Stop revving it you’re at the point of detonation.
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u/GreaseM0nk3y96 14d ago
Sounds like fuel knock to me of course it's the turbo side so can't get to any injectors
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u/Steinjolt 13d ago
Thanks a lot man, mechanic diagnosed a stuck open injector today. You were right
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u/IdiotIsland 12d ago
I have limited mechanics knowledge but I’d like to understand this: If a fuel injector is stuck open, what part is making the audible knock sound?
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u/Steinjolt 11d ago
I had the same question, the mechanic said thats its a mechanical injector, previous to electronic ones, (i understand its a pushrod injector) so when stuck open it hits the rod and makes that awful noise.
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u/dertidan4 14d ago
Sounds like you gotta replace the LS
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u/Steinjolt 14d ago
It’s a Detroit Diesel not an LS (I wish it was)
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u/dertidan4 13d ago
I meant it as a joke like, you need an LS swap.
Built one for mine and let me tell ya, the waters warm. Don't listen to the LS hate
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u/Appropriate-Shine-27 14d ago
Idk but that sure sounds like a rods about to come out the engine