1998'ish Case 550G. Runs fine for a while, then under load will lose rpm and barely run. I'll let it idle a while and it'll run a while then repeat. I drained and flushed the fuel tank, flushed the lines, cleaned all the banjo fitting orifices, replaced filters, cleaned the tank vent, new injectors, new lift pump. Basically everything new except the injector pump. I don't want to spend 1K for troubleshooting with a new injector pump. It doesn't overheat. I'm down to a potential air leak, but the rpm drop is so sudden that an air leak doesn't make sense. Engine has good compressions and oil pressure. When it's running right it runs like a new one. Any ideas would be appreciated.
If it has any rubber hose in the fuel system it could be delaminating on the inside and causing a partial blockage at times. Wouldn't be too expensive to replace all the rubber lines just to eliminate that possibility.
True, I'll add it to the list of **** to do. Thanks.
How about plumbing a pressure gauge into the inj pump inlet and check pressures before/after replacing the rubber.. Could it be a vacuum at the fuel tank.??
The tank vent is free, and I ran it with the cap off to be sure. I'll replace the rubber hose and see if it has any affect. There's only about 4' of rubber hose from the tank to the lift pump. If I still have issues I'll look at the pressure gage suggestion. Thanks.
When you say it "loses power under load", is that hydraulic load or transmission? Does just pulling a lever & cycling a circuit to it's stop point & hitting main relief pressure stall the engine? Do you need to be operating the transmission & stalled in a big pile of dirt or against a tree? OR a combination of both? Can you measure the engine RPM while doing the individual / combined stall tests?
Transmission load pushing dirt. Hydraulics are unaffected. There's no tachometer. It'll push a full blade just fine until it fails suddenly and it's always when pushing hard. It'll bog down and barely idle. I'll let it idle 5 or 10 minutes and then It'll rev up again. Time from startup to 1st fail can be up to an hour. The time between failures diminishes with every iteration until I limp it back to the barn.
Some other things to check, does this model have return lines running back to the tank? I've had odd issues with Case/Cummins powered equipment in the past when the return line gets partially plugged. If fuel can't get out of the injection pump it can't get in either. You said you flushed the tank, how involved did you get in that? I've had a tiny object in a fuel tank cause hours of consternation before. Sometimes a small object falls in the tank and is too big to go out the outlet, so unless you physically can see it and pull it out, all the flushing in the world won't work. Most recent issue I had was a little 1" square paper price sticker, presumably off a new funnel I had used, would intermittently plug the fuel flow out of the tank on my Kubota tractor. It could be injection pump or injector related. I've had injection pumps (with high hours on them) lose pressure when they get hot. As they get hot the case expands and opens the clearances (which are already larger than they should be due to wear) enough to cause low power, stalling or a no hot-start condition. Next time is starts acting up pour some cool water over the injection pump and see if it clears up. Same with injectors, we had a JD tractor recently with bad injectors, would run great for a while then start acting up. Seemed to be time/temperature related, new injectors fixed the problem. Again, when they got hot, clearances started expanding and they quit working properly.
Good points thanks. I thoroughly cleaned the tank. Found two fuel can spouts in it. I'll try the water trick on the pump. The injectors are brand new.
I hate those fuel cans. I pulled a part of one of those spouts from a Case IH tractor earlier this fall. I remember when it fell in years ago, but it is so much work to get that tank off I left it in there.
If u have a rotary inj pump on the engine, DO NOT POUR WATER ON IT WHILE ITS RUNNING.!!! Rotary pump, steel lines come off the pump “in a circle”.. In-line pump, “the steel lines are in a straight line.. The pump WILL SEIZE UP.. due to drastic temp change.. Good luck
Not disputing what you say, but when I do that I just slowly pour a little water from a bottle over it, it's not like I'm dumping a cooler full of ice water on it. Maybe I'm just dumb, lucky, or both but have done it many times without ill effect. This is a common diagnosis procedure for no-hot-start conditions on 7.3 IDI Fords and I've found it to be true on other rotary pumps as well.
Nonetheless, being a 1998 model there is a good chance it has an inline pump on it.
Any luck?