Help narrowing down a 6.2 knock?

[Matt1031]

My 6.2 is making an unusual knock and I'm trying to narrow possible causes.
Here's the history/symptoms:

Truck is new to me. It sat for a pretty long time before I got it. Has 1/2 tank of fresh fuel and I've put about 150 miles on it. Oil level's good, oil pressure's good. Looks like typical dirty diesel oil - black, no sparkly metallic stuff.

Engine knocks under load, especially at part throttle. No knock at idle, no knock once it gets up to speed/full throttle.

Doesn't sound like it's coming from bottom end, it's a light knock and it sounds/acts similar to how detonation would sound in a gas motor.

So here's what I'm thinking:
Bad injector? (No white smoke so it can't be too bad)
Ate a glow plug? (Glow plugs are inop due to bad relay)
Piston damage from use of ether (It's been ether started a few times)

I have a fair amount of work to do on the electrical system before I can really get into the engine, but has anyone come across this before? What's the best way to rule out a dirty injector before I go tearing apart the engine? Would an a glow plug damaged piston make a noise at idle?

Thanks, Matt

 

[AllenEM]

sounds like mine

 

[skinnedknuckles]

Wrist pins?

Paul in Janesville, Wis

 

[Matt1031]

sounds like mine

I drove a lot of 6.2 equipped vehicles in the Army - none of them made this particular sound. I'm hoping it's just an injector acting up and not a top end problem.

I guess there's no real way to know until I tear into it.

 

[Dave Kay]

If it were me I would park that truck and go over it with a fine toohed comb. Many a potential catatrophe can be avoided by looking for the obvious. This knock could be something simple like a broken motor/trans mount or a loose air cleaner mount. But if you look at the many postings here on SS regarding broken stater bolts, sheared harmonic balancer keys, worn and slipping harmonic balancers pullys, et., al., you'll get some idea of what kind of mechanical disasters could be waiting for you if the truck continues to be driven with this knocking sound un-diagnosed. Get to studying the TM's and get familier with the basic maintainance and troubleshooting; you'll be surprised what you may find. Heed my warning and park the thing until you eliminate the cause of the knock.

 

[Barrman]

Check your torque converter bolts and flywheel bolts too! They sometimes only make noise when under a load at low speeds.

 

[Matt1031]

Well... Still working on it, but I think I have it narrowed down some more.
I replaced both batteries today with new group 31's and that alone seemed to magically fix half of my electrical issues. So now that it starts somewhat reliably, I figured I'd better steam clean the massive amount of mud, grime, and crud off the engine and trans to make my job of working on it a little easier.

On a whim, I put an entire container of diesel injector cleaner in the tank before driving to the car wash, and the knock quieted down a LOT after a couple miles. I figure now that the engine isn't covered in mud and grime I can actually work on it, so I'll be checking the torque converter and flex plate bolts tomorrow just to be on the safe side. I think the fact that a $5 bottle of injector cleaner quieted it down significantly confirms that it's probably a fuel or spray pattern related issue. Maybe It was just a bad tank of fuel?

I have to fix an O-ring on my pop tester before I can start checking the injectors, but once I get it 100% figured out, I'll post up results.

Thanks for the help and suggestions!
-Matt

 

[southdave]

I have knock it less when I replace one bank of injectors, still have to do the other side