Kubota D-722 engine assistance
Recently, I obtained a generator which is powered by the 3 cylinder Kubota D-722 engine. It drives the Onan generator. I am caught between Onan and Kubota with each telling me a different story.
Background, this unit is a 1998 model that has never been installed or even started, with 0 hours. It was purchased to go into a bus/rv conversion but the project never got off the ground.
I have been researching what I need to do before starting it such a checking for mice, etc. The areas where I am confused surround the Oil pressure switch and the Water temperature sending unit.
The unit has an Onan multi gauge panel with oil pressure, coolant temp, and voltage gauges, start/stop switch and hour meter. The gauge panel is pre wired and simply plugs into a plug that leads to the control board.
According to Onan, the oil pressure sensor is not an Onan part but came with the engine but Kubota can not confirm that as most of the literature for this engine was given to Onan as part of the contract. It is listed in the Onan parts book as 185-5492. According to Onan, this pressure switch is monitor by the generator inverter/converter and reads either 0 or 50. Apparently, the oil pressure gauge displays 0 if no oil pressure and 50 when the oil pressure is normal. They also state this system is not reliable and if the owner desires a true reading, an after market oil pressure gauge should be installed. Other than using a “T” with the current oil pressure sending unit are there other locations an after market could be attached? Onan and Kubota are both unable to determine the thread size of the current oil pressure sending unit or the hole in the block.
Now, the coolant temp sending unit, which is identified in the Onan parts booklet as 193-0318. Some have stated this unit is a simple open/closed threaded switch that the control board communicates with before allowing the engine to start, then if the switch moves in the other direction, the control board senses that move and shuts the engine down. Others say it is a resistor that as the temp increases, the ohms go down. It is unknown how accurate this may be.
Regardless, the main issue with this sensor that many times it will corrode making removal almost impossible. Multiple owners have posted their issues with removal. It seems there a 2 schools on this issue. The sender simply turns out with no problem or the other is that hours are spent attempting to remove this sensor and may times this results in cracking the lower part of the thermostat housing. In order to replace that housing, almost the entire front of the engine must be removed to include the head. Some photos have shown green corrosion in the hole where the sensor probe was inserted into the engine. Some say this location for the temp sensor with the probe sticking in the engine slow the flow of coolant contributing to the formation of the corrosion. Seems this occurs regardless what anti freeze is used or how often it is changed. Once again, Onan and Kubota are unsure of the thread size of this sender or the hole as if this sender or another sender can be installed on the engine. Also, seems reasonable to install an aftermarket gauge to get a accurate reading.
I looked to see if there was an interchange sender for either oil or coolant but did not find any and Kubota is unable to assist.
Could other sending units be used and can one find another location to move the temp sending unit? I would be interested if anyone has had any issues with their D-722 and any suggestions. I understand your experiences may be in a tractor but many of the things should be the same on the engine regardless of its application. I appreciate any input.
Recently, I obtained a generator which is powered by the 3 cylinder Kubota D-722 engine. It drives the Onan generator. I am caught between Onan and Kubota with each telling me a different story.
Background, this unit is a 1998 model that has never been installed or even started, with 0 hours. It was purchased to go into a bus/rv conversion but the project never got off the ground.
I have been researching what I need to do before starting it such a checking for mice, etc. The areas where I am confused surround the Oil pressure switch and the Water temperature sending unit.
The unit has an Onan multi gauge panel with oil pressure, coolant temp, and voltage gauges, start/stop switch and hour meter. The gauge panel is pre wired and simply plugs into a plug that leads to the control board.
According to Onan, the oil pressure sensor is not an Onan part but came with the engine but Kubota can not confirm that as most of the literature for this engine was given to Onan as part of the contract. It is listed in the Onan parts book as 185-5492. According to Onan, this pressure switch is monitor by the generator inverter/converter and reads either 0 or 50. Apparently, the oil pressure gauge displays 0 if no oil pressure and 50 when the oil pressure is normal. They also state this system is not reliable and if the owner desires a true reading, an after market oil pressure gauge should be installed. Other than using a “T” with the current oil pressure sending unit are there other locations an after market could be attached? Onan and Kubota are both unable to determine the thread size of the current oil pressure sending unit or the hole in the block.
Now, the coolant temp sending unit, which is identified in the Onan parts booklet as 193-0318. Some have stated this unit is a simple open/closed threaded switch that the control board communicates with before allowing the engine to start, then if the switch moves in the other direction, the control board senses that move and shuts the engine down. Others say it is a resistor that as the temp increases, the ohms go down. It is unknown how accurate this may be.
Regardless, the main issue with this sensor that many times it will corrode making removal almost impossible. Multiple owners have posted their issues with removal. It seems there a 2 schools on this issue. The sender simply turns out with no problem or the other is that hours are spent attempting to remove this sensor and may times this results in cracking the lower part of the thermostat housing. In order to replace that housing, almost the entire front of the engine must be removed to include the head. Some photos have shown green corrosion in the hole where the sensor probe was inserted into the engine. Some say this location for the temp sensor with the probe sticking in the engine slow the flow of coolant contributing to the formation of the corrosion. Seems this occurs regardless what anti freeze is used or how often it is changed. Once again, Onan and Kubota are unsure of the thread size of this sender or the hole as if this sender or another sender can be installed on the engine. Also, seems reasonable to install an aftermarket gauge to get a accurate reading.
I looked to see if there was an interchange sender for either oil or coolant but did not find any and Kubota is unable to assist.
Could other sending units be used and can one find another location to move the temp sending unit? I would be interested if anyone has had any issues with their D-722 and any suggestions. I understand your experiences may be in a tractor but many of the things should be the same on the engine regardless of its application. I appreciate any input.
