I just bought a 1986 F-250 6.9L diesel and it just started to knock as I drive and not really at idle, but it doesn't sound like it is internal, I was hoping someone might have an idea what it could be and how to fix it? Thanks

 

It could be a fuel knock you can crack injector line and see if the knock goes away

 

Thats an indirect injected motor, you could have an injector getting sloppy. See if you can pinpoint the cylinder its knocking on like Coyropin said, and then you can swap the injector with another and see if the knock moves with the injector. If you have to replace one, I would just go ahead and replace them all.

 

alright I will do that this weekend thanks a lot guys I appreciate it!