D-239 injector pump

The 574 is still a one hour tractor. I've tried the simple stuff, drained and strained the fuel tank, new hose, it only skips under a load so I can't fool with the injectors.

I understand there is a fuel pump built into that Bosch injector pump and it has been suggested that it takes about an hour of load to warm things up enough for the seals and etc. to start leaking. It did not cool off enough in 45 min. to run without missing.

What do you think?????

It definitely sounds like a fuel related problem. I can't remember if this was mentioned on your earlier posts, but I have seen the spring loaded metering needles in injectors with alot of hours on them start binding and opening at too high a pressure, or stick open after the engine has gotten good and hot. But they work OK with a cool engine and on the pop tester. I guess I would start cracking injector lines when it starts running rough and see which one or ones affect the running the most. The worst problem with your situation is that it only does it under load, making it difficult to do that. You would really need something with a constant PTO load, like a dyno, to do it. The only other option is to have the injectors rebuilt, which might not be a bad idea anyway if the tractor has many hours on it, and if that doesn't take care of it, pull your injector pump and have it rebuilt. I had a MF 298 with a CAV pump that did this same thing, now that I think about it, probably over 20 years ago. After testing injectors, checking valves, compression, etc., I began to think that maybe the advance piston in the pump was sticking when it got hot. I pulled the pump off and had it rebuilt and it has run fine to this day. Sorry this is so long, but I started remembering things while I was typing. Good luck.

One more thing you might try if you haven't already is adding diesel fuel conditioner to your fuel. Todays fuel doesn't have the lubricity it used to in the old days and I don't dare run anything without conditioner these days.

Thanks, I just talked to my tractor mechanic and he said about the same thing. Put it on the dyno until it starts missing and then start replacing things. I really don't know if I want to put another grand into this tractor. I am going out to mow right now and will see if it lasts a hour starting cold. Thanks again.

Bill