Seeking: Old school Diesel Guru/ Pundit.

This one continues to kick my backside. 1983 f250 6.9 Diesel with Banks turbo. 100K original miles. Knocks like the end of the world is at hand. Runs like new. Took it to several very reputable local shops and all said it "needs a motor"   Pulled injectors one at a time and discover that when one of them is unplugged that all knocking stops. Replaced that injector with a brand new one, and.... It knocks exactly as it did with the old one. So many questions like if the motor was bad wouldn't it continue knocking when the injector was unplugged?       So what do you all think? New injector also bad? Motor just bad? I'm bad like Michael Jackson?  

I would *think* (and I'm inviting myself in despite NOT being a diesel expert by any means) that it's rod knock, and when you pull that injector, that cylinder isn't firing, and the pressures stay much lower. Thus, no (or much less) knock.

That is, the injector itself has nothing to do with the noise, but shutting that cylinder down stops working that rod hard enough to make it knock.

When you say you pull the injector, are you removing it or just loosing the injector line?

It might be a good idea to drop the pan and visually inspect the rod bearing for the cylinder with the knock. 

Another vote for rod bearing or wrist pin.  No fuel means no combustion, means less noise.  Can you get away with dropping the pan and slipping new bearings in?

I'm going with rod knock or broken piston skirt

In reply to wae :

Next step!    We think the old truck is worth saving.

I am wondering how an injector was unplugged on this truck.  Unless you were unplugging a glowplug.

describing a wrist pin or cracked skirt

Get a borescope and scope all cylinders. Bet you'll see something interesting. 

Injectors are pretty much just poppet valve that open at a certain pressure from the injector pump, so they are quite reliable compared to the newer electronic ones. Most likely it is something wrong with that cylinder. 

If the truck is solid it's probably worth fixing , it looks great as it sits now 

but how many had diesels ?

maybe an old city maintenance truck , or fire department pick-up,

Good luck

Might be an opportunity to slide in a 7.3 IDI short block in place of the 6.9?

For sure worth an engine swap, those trucks are not cheap, especially for one that's not rusty.

Definitely worth saving. It lived in Cali very near Banks place and got a Banks Turbo early in its life. Was set up for a slide in camper and I can imagine it traveling happily throughout the USA of the the 80s. Has just over 100k original on it. And if everything was in order I would consider it an overdrive short of a very happy meal.     I hear the hive clearly but the knock is still a bit of an enigma to me given the condition of the rest of the truck. Guess I will continue making SURE its not the fuel system before attempting a -very- heavy motor swap.    Willing to pull the pan and inspect that cylinder but what specifically to look for if I do that?      

I would say pull the bearing cap off on the road the noise is coming from?

And look up the bore to see how the wrist pin and piston skirt look, maybe even some gentle prying between them for play

Hate to be the one to say it.  It's so cliche anymore.  But here goes:

Fummins