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?

 

[boomer1025]

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?

Sounds like you have a fuel knock, I'd remove all 4 injectors and check the tips and make sure one didn't split. If the tips are ok, then I take and have them tested. If it's been this way since it was rebuilt, then I'd have the pump timing checked also.

 

[Ford tractor]

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.

Not on a diesel. White smoke indicated unburnt fuel.


OP -

You need to pull that 4th injector and replace. It sounds like you have one that is leaking or popping at low pressure

 

[knightrider955]

Not on a diesel. White smoke indicated unburnt fuel.


OP -

You need to pull that 4th injector and replace. It sounds like you have one that is leaking or popping at low pressure

I guess I'll try to get it out. Couldnt budge it when it was cold. Maybe I should run it a little then try? Its just a pressed in injector.

 

[David-Davies]

Hello Knightrider955. I think that you have an ejector problem. The reaso that your rain cap banges, is because it just mised, and closed. When it fires it flyes open. To test. Crack one enjector line at a time. When you crack an enjector and it makes no difernce, it's the bad one. All the rest will make it run worse. If you have white smoke at low speed or light load, who ever ground the valves may have exceded the recesed hight of the valves.[ground them down too far] There is usely only about .025 to play with. The so and so that did my head did that, so I have white smoke at low speed, or load.
David-Davies

 

[gregharr55]

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?

It is never a bad idea to get the injectors checked and the injector pump checked. This is the MOST overlooked maintenance item except for maybe valve adjustment if the model tractor requireds it!!!!!!!!

 

[tcartwri]

Some diesels have a free swinging counterweight on the crank. This could also be the sound you are hearing.

 

[fieldserviceengineer]

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.

White smoke in a diesel is indicative of unburned fuel. You have replaced 3 injectors, time to get the last one. Are those three new of 'newer' than the originals? Low VOP (valve opening pressure, POPPING) allows for a more coarse fuel spray and incomplete combustion. The oil smoke could well be due to the cylinders are washed down with fuel and thus you have ring wear. You can live with that more than you can tolerate the fuel injection problem. Replace all four injectors with units from a pump shop. Or have the three tested along with the repair or adjustment of the 4th. Likely the injector tip holes are worn and allow more fuel flow at a lower pressure. Meaning the fuel is not atomized sufficiently to get more complete combustion.