Kohler ECH730 EFI Fuel System Issues

Sharky

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Hello, I have a Miller welder with a Kohler ECH730 engine, in the shop with an EFI issue that I can not seem to solve. The engine runs well for the first 10 minutes or so, but once warmed up and in "closed loop" operation, it will start to starve for fuel, then recover and run fine. It does this continuously every 15-20 seconds. Kind of like a surge as if it was about to run out of fuel. As it is dying, the electronic governor gradually opens the throttle in an attempt to maintain the RPMs. I performed a running fuel pressure test, and the fuel system maintains 38 PSI. This is good, according to Kohler specs. I have eliminated the fuel system on the equipment and fed the engine with a remote fuel tank, and no change. I tried pulling the fault codes, and no codes were stored in the system, even after running for awhile. I pulled the unit apart, checked, cleaned, and tighten the main ECU ground behind the flywheel shroud, as this was a known issues on earlier models, and again no change. I re-flashed the ECU, and performed a TPS reset, again no change. I am lost !! Although I have 22 years experience, I am relatively "green" when it comes to EFI. As I said, there are no fault codes to lead me in the right direction. If I dribble a small amount of fuel into the throttle body as it is dying, It will recover as I am feeding it. Has anyone else run into this issue ? I am thinking either a bad ECU, or O2 sensor, or engine temp sensor, but not really sure, and don't want to just start changing parts. Any help would be greatly appreciated. Thanks !!:mur:
 

motoman

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Sharky, I have fussed with the auto EFI at home. There are some things the ECU takes for granted so maybe back up and check stuff any motor needs. Take a look at plugged line , plugged fuel filter. I once had a similar experience with a car and finally found a partially plugged fuel line which would starve the carb float bowl, recover , then refuse throttle enrich, over and over. I still don't know what the stuff was blocking the line. It looked like a filter from a filter cigarette. Try a substitute pressure regulator, injector, fuel pump if you can avoid having to buy them. Borrow a spare ECU from a shop if you can find one. Good luck.,
 

Sharky

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Apr 20, 2017
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Sharky, I have fussed with the auto EFI at home. There are some things the ECU takes for granted so maybe back up and check stuff any motor needs. Take a look at plugged line , plugged fuel filter. I once had a similar experience with a car and finally found a partially plugged fuel line which would starve the carb float bowl, recover , then refuse throttle enrich, over and over. I still don't know what the stuff was blocking the line. It looked like a filter from a filter cigarette. Try a substitute pressure regulator, injector, fuel pump if you can avoid having to buy them. Borrow a spare ECU from a shop if you can find one. Good luck.,

Hi motoman, The fuel filter(s) are new, Fuel lines and tank were flushed and are clean. I even went as far as taking a totally separate fuel tank and line with known fresh fuel, and attempted to run the unit that way, eliminating the equipment's fuel system, and no change. Fuel pressure is a steady 38 psi at the fuel rail. My Kohler rep has requested a video of the unit running to try and trouble shoot what might be the issue. I am hoping to attend a Kohler EFI school in the near future. Just waiting on my rep to put one together.
 
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