My 2004 20EOR Kohler (Yanmar diesel, 4500 hrs) generator runs great, starts easy and has good fuel economy. It has been serviced regularly and has been trouble free. Recently it stumbled for a brief moment but the engine never stopped. My service technician suspected an air bubble in the fuel system so all of the rubber fuel lines were replaced. There were some signs of cracking in the eight year old hoses.It worked well for several days.Ten days later after the hose replacement, it stumbled again just for an instant but the engine continued to run like nothing happened.This time my mechanic scrutinized the schematics and determined the relay board was the probable culprit. The Kohler service manual also seemed to confirm this.The brushes and all other important wires were within spec and the electrical connectors looked good. The relay board was replaced and the generator worked several more days without incident then on May 14th it stopped suddenly. I called for a rental generator to be delivered and while I was waiting I restarted the generator without a problem and it ran for two hours without incident before I stopped it myself. I studied the schematics and trouble shooting guide and discovered the Low Oil Pressure (LOP) and High Engine Temp (HET) switches. These are Normally Open switches wired in parallel so if either switch detects an alarm condition, the switch closes and ultimately shuts the engine off to prevent serious damage. Could it be that one of these switches is malfunctioning prematurely? The coolant temp (165 deg) and oil pressure (45-60 psi) are normal according to the analog gauges and I've confirmed engine temp using an IR temp instrument. I have ordered new LOP and HET switches and will have them installed in a week or so. Until then, I'm at my witt's end trying to solve this problem. I will note that on all three occasions the generator had been running for about an hour and had not been run for at least two days before hand. I will also add that the fan belt broke last summer and the generator temp increased to the point where it shut itself off before I could catch the problem. In this instance, is it likely or even possible that the overheating situation had altered the HET switch to the point where it is not dependable or accurate anymore? I am eager to test the old switch when it's removed and see if it closes prematurely in a pan of heated water. I don't want to keep changing parts without finding the smoking gun but I feel we are running out of things to test and replace. I did disconnect the HET switch from the system and ran the generator (supervised) for a total of about 20 hours without incident. This doesn't rule out the HET but I'm still wary. Can you offer any insight? Thank you. David
Country: United StatesMake: KohlerModel: 20EOR generatorYear: 2004Engine: Yanmar 4TNE84T
Replaced rubber fuel lines, replaced relay board.
I was taught many years ago that anytime engine overheated, change the thermostat. It is filled with a wax like substance and it can be damaged by the overheat, It is a working item and has to open and close many times to regulate the temperture. If it sticks even momentarily, you could get spike in temperture and HET could shutdown engine. Just my thought. Thank you.