Need some help

[Goosefoot]

I have a 2000 L2500DT. It's been loosing power after mowing about an hour, it straightens up after several minutes then looses power intermittently. When it cuts out, i can push the throttle open and it does not respond. I hold the throttle open and it takes several seconds for the rpms to start to climb. temperature gage is at 3/4. Today I replaced the thermostat, I checked the old one by placing it over a burner on my stove, it did not open. I also drained the gas tank and replaced the fuel filter. I didn't get to put a load on the tractor, but let it run for an hour with the radiator cap off. The water never circulated though the radiator, but the temperature gage didn't get above halfway. Will the water circulate with the cap off or does it have to have cap on to build pressure?
The diesel drained from the tank had no debris in it. I'm going to work with the tractor tomorrow, if it cuts out, what do I do next? Water Pump?

 

[Dave_eng]

I dont know your model of tractor specifically but it sounds like you have a fuel delivery problem. Is there a low pressure lift pump to supply fuel to the high pressure injector pump? If so this would be my first suspect.
The water temp issues have nothing to do with the running problems you are describing. Your engine is not getting the fuel it needs.
Are you checking the thermostat submersed in water on the stove or just hanging in mid air? It needs to be tested hanging suspended in the water on the stove so it does not touch the bottom of the pan.
Dave M7040

 

[Dave_eng]

The rad cap has nothing to do with circulation. It just raises the boiling point of the water or coolant especially at higher elevations. For example at the top of Mount Everest water boils at so low a temp it is hardly warm. If you were operating your tractor there without a rad cap the engine would not get the cooling it needs and fail as boiling coolant does not carry away enough engine heat.
Does the fuel cap allow air into the tank?
It should otherwise a vacuum builds up as fuel is drawn out. Try running the tractor with the cap loose or off to see if the same lack of power develops. Is there a hissing sound when you remove the fuel cap when the engine starts to loose power? This is a symptom of the cap vent being plugged sometimes by flies which use mud to build nests.
Dave M7040