Cat D3B Running poorly, Need advice

Here are the symptoms:
1) Idles fine, no problems, for hours.
2) Can crank throttle up to full if not working, runs fine.
3) Start working and after about a minute give it more than 1/2 throttle, starts sputtering. Black smoke. Turn down to idle will recover.
4) Start working again will again start sputtering.
5) Let it idle for 15 mintues will work well again for about a minute, then the problem starts all over again.

OK, I"ve never had an injection pump go bad before, is this a symptom? I don"t know what else it could be other than bad fuel, and I have 3 other machines running on the same fuel with no problems. Any other recommendations?

Thanks for any input.

I have a D-3B 27Y that used to burn 3 litres of oil in 8Hrs,had lots of blowby had 1 broken piston skirt and cracked rings on 1 piston, and kept on working without an engine miss.Rebuilt it with aftermarket 3 ring pistons.

I do not have the ability to test the fuel pressure. I opened up the fuel pump and the oil ring on the cover does not fit as it should, perhaps that is the problem. I'll get one tommorrow and replace. Is a total fuel pump rebuild very hard?

It still seems like I am missing something. This happened all the sudden. Is there another fuel filter than the spin on one? In the manual it shows a screen on the injector pump. My machine does not have this or a priming pump on it.

My guys and I do all of the maintence and repairs, althought this machine has required very little except some starter work, and regular maintence.

Usually in 3rd gear full throttle with the brakes applied it would stop, but not bog out. With the current operation it would stall and sputter.

I am probably going to get the Cat service team out to look at it. I guess it could be anything, stuck valve, intermittent head gasket failure, stuck return line. Who knows, I appreciate your time and help.