OC-6 diesel issues

[Hap420]

I"ve got an OC-6 diesel that has a bit of a problem when warmed
up. It starts right up and runs great, but i"ve been harrowing with
it and after running it for about a half hour under a pretty good
load it will bog down and start blowing black smoke. After a few
seconds it will kinda pop and take off again running strong with no
smoke. Any ideas on what the culprit could be would be greatly
appreciated. Thanks

 

[Tramway Guy]

Do you step on the clutch when it bogs down and does it still lug down when you do?
Where is the 'pop' coming from?
The black smoke most likely is because something is overloading the engine, or there is a restriction in the air supply or exhaust.
Overloading can be anything from something tightening up in the engine to a dragging steering band in the rear end, or even a bad hydraulic pump.

 

[Hap420]

the pop comes from the exhaust and then the smoke clears right up. i have had the hydraulic pump rebuilt and the brake bands are adjusted properly. its almost as if one cylinder stops firing and then a few seconds later kicks in again. it only happens when it has a good load on the engine, like when pulling a harrow or plow. thanks for the reply

 

[Tramway Guy]

I am thinking that maybe a valve is not seating properly, check your adjustment.
Might also be an injector nozzle is sticking open; that would dump fuel into the cylinder at the wrong time and would not burn properly, so you would lose 1/6 of your power, but still pumping all of the fuel. The black smoke results from unburned fuel.
Bottom line is you have a weak cylinder at times. The hardest thing is to find it. A very messy way would be to remove the exhaust manifold and monitor the individual cylinders; it should be obvious which one it is when the symptoms recur. My guess is that 5 of them will have black smoke and one will not.