I have a Kubota 905D engine used as a power source on a generator set, powering an irrigation system. It has between 4-6,000 hrs on it, well maintained. Proof meter has been replaced a few times over the years. Does not burn oil, starts reliably and has been a good unit.
The throttle is mechanical, fixed, and set to run about 1,800 rpm (480v output from generator). There is no input or control to the throttle, it is fixed at the required rpm. It has a mechanical governor in the injector pump body. I found the machine mid-cycle as it was irrigating the field, but had stopped due to low engine speed. I estimate the engine is idling at about 300-400 rpm, well below a normal idle and a fraction of the fixed speed previously mentioned. Air intake system is clean, fuel filter replaced, fuel line replaced, have return fuel flow to the tank as expected. Engine will start right up and it sounds like it is going to ramp up speed for a second, but immediately resumes low idle. I have taken the throttle assembly cover plate off the pump and see two springs (one large primary and a smaller secondary) that match parts listings that I have been able to find. I see no obvious damage in that cavity and the rack (?) seems to move freely. I did not run the engine with that cover off to see if moving the linkage would effect anything since it looks like that area gets oil splash from the crankcase and didn’t want to create an unnecessary mess. I tried moving the throttle itself and had no effect on engine speed.
I have a short video I can share but can’t post it here. Anyone have any idea what might be going on?
The throttle is mechanical, fixed, and set to run about 1,800 rpm (480v output from generator). There is no input or control to the throttle, it is fixed at the required rpm. It has a mechanical governor in the injector pump body. I found the machine mid-cycle as it was irrigating the field, but had stopped due to low engine speed. I estimate the engine is idling at about 300-400 rpm, well below a normal idle and a fraction of the fixed speed previously mentioned. Air intake system is clean, fuel filter replaced, fuel line replaced, have return fuel flow to the tank as expected. Engine will start right up and it sounds like it is going to ramp up speed for a second, but immediately resumes low idle. I have taken the throttle assembly cover plate off the pump and see two springs (one large primary and a smaller secondary) that match parts listings that I have been able to find. I see no obvious damage in that cavity and the rack (?) seems to move freely. I did not run the engine with that cover off to see if moving the linkage would effect anything since it looks like that area gets oil splash from the crankcase and didn’t want to create an unnecessary mess. I tried moving the throttle itself and had no effect on engine speed.
I have a short video I can share but can’t post it here. Anyone have any idea what might be going on?
