Knocking Diesel. Any ideas?

[knightrider955]

My Diesel has a knock but only at low RPM's and at idle. And its not continuous. Its a spuratic knock and everytime it does it, the rain cap on my muffler jumps at each knock. Has anyone ever seem this or know what causes it?

 

[RoyJackson]

Could be a rod or main bearing. Low RPM can result in the main bearings being "pounded" which is not good.
How low an RPM do you run? You might want to consider upping the idle RPM (I use 1200-1500 RPM).
The only time I use a lower idle is when engaging the PTO (reducing the shock load) and even then I've got my foot on the throttle to "blip" the throttle if the tractor bogs down.

 

[kjung17]

Perhaps a weak injector over fueling at low rpm?

 

[knightrider955]

I thought maybe rod or main bearing but I dont think my rain cap would hop higher each knock if it was that. I did change three injectors with brand new ones. The fourth one I couldnt get out. Maybe that injector has issues? Also it smokes constantly It lightens up on higher RPMS but the smoke is white with a tad of blue and smells like fuel. Doesnt use any oil. Supposedly it was completly rebuilt just before I bought it. The guy did have reciepts though. It makes great power and I use it like this all the time.

 

[kjung17]

I hate to point this out, but you've eliminated 75% of your injectors. I hope it's not in the pump. Your graphic is hilarious.

 

[knightrider955]

Thanks! If it was the injector pump, I could live with dropping 600 on a new one as long as it was fixed.I just dont know much about diesels. Also there is hardly any blow by. Maybe low compression??

 

[kjung17]

Thanks! If it was the injector pump, I could live with dropping 600 on a new one as long as it was fixed.I just dont know much about diesels. Also there is hardly any blow by. Maybe low compression??

White smoke usually indicates a lean condition. A compression test would be prudent that old girl. Sorry, I'm not too familiar with the specifics of that tractor.

 

[knightrider955]

Would injector timing play any part it this?

 

[kjung17]

Not out of the question. How many hours on machine?

 

[knightrider955]

Ive only run it about 10 hours since the rebuild but it was rebuilt by a private owner so maybe he didnt get it set right?