Kohler 26 EFI

Discussion in 'eXmark' started by robsrod, Apr 7, 2006.

  1. robsrod

    robsrod LawnSite Member
    Messages: 1

    I have a xMark with a Kohler 26 EFI and it is running rough the majority of the time. I have read through the forums and understand if there is a problem that the ecu instruct the engine to run rich. But how do you find out whats wrong? Their is no engine code light on. The unit runs just seems to run rich. I don't know where to begin to look. Grounds exhaust? O2 sensor? I checked the plugs and they are black from being rich. I couldn't find any solutions mentioned in the forums to the 26 EFI rough running problems? Can anyone help or suggest where to begin? How about the Oldguy?
  2. DEEJ

    DEEJ LawnSite Member
    Messages: 230


    OK, you are describing a problem I had with my '01 26HP EFI Lazer.

    The issue was water getting into the big connector plugged into the ECU. This happened after I washed it with a regular hose. I just got the water where it should not have been.

    On this machine the ECU is located down under the back of the machine. On my 03 lazer it is mounted higher on the frame beside the engine block. I removed the connector from the ECU and sure enough things were damp in there. I used light air pressure to dry the ECU connector and the mating connector on the harness. I then let it sit overnight with a fan blowing on them, just to be sure all moisture was out.

    I bought a tube of electrical contact grease and coated both connectors. I mated and unmated the connector 3 or 4 times to clean the contacts, added a bit more grease, and put the connectors together one last time.

    From the first turn of the key it has run flawlessly since then (2 years ago). The electrical contact grease helps water proof the connection, but I am still careful to not fire water directly in the area of the ECU.

    I believe I heard at the time that there is an Exmark service bulletin out about this very thing. The service bulletin calls for exactly what I did. If I am not mistaken it also called for the technician to mate the connector and seal the joint with silicone to keep water out. I could be wrong - maybe the silicone was simply something I intended to do if required (and it wasn't).

    A little water in the wrong place is a bad thing with the EFI units. Oddly enough I have never had this problem with my '03.

    The other possibility of course is the age old ground issue. Clean the ground connections everywhere - to the frame, to the engine - make sure all paint is removed, sand the metal for good contact, apply some electrical grease, and make sure the connecttions are tight. This was a problem with the early 26 EFI units from several manufacturers. The manufacturers didn't realize how important good grounds were with the EFI engines.

  3. 11baron

    11baron LawnSite Member
    Messages: 13

    Your description is a perfect example of what is going on with my machine. After turning the ignition on-off on-off on, in less than two seconds, my MIL spit out a code 42. Which is the temperature sensor. The ECU is not able to detect the engine (oil) temperature and therefore defaults to a preset fuel curve, which happens to be RICH and the thing runs like crap. Well mine does anyway. It has run this way ever since the dealer serviced it to a tune of 800 bucks. Normally I do my own servicing but did not have time last season.

    Try to see what code your MIL sends back to you after turning the ignition on and off according to the patter above. If you have already done this, then I don't know.


  4. lazer9284

    lazer9284 LawnSite Member
    from florida
    Messages: 50

    If it is running rich, and you dont get a code in the first few minutes of run time , or its an intermittent problem .
    I would check the muffler/o2 sensor.
    if no code then o2 sensor is workink and there is a small leak or crack in the muffler.
    What is happening is the o2 sensor is sending signal for lean run... so fuel is dumped into engine to compensate.
    Then you get ruff run, black smoke rich condition.
    o2 sensor is picking up all that extra oxygen in the exaust from the leak and adding fuel. so it thinks it is normal thus... no code.
    get a new muffler and problem will be fixed. It happened to me on an efi i had a couple years ago. I bumped into something and didn't notice that the exhaust manifold had cracked at the weld into the muffler.
  5. 11baron

    11baron LawnSite Member
    Messages: 13

    I recently replaced the oil temp sensor with an upgraded version that also included an additional ground from the starter to the ECU. I no longer get code 42. At the moment my problems seem solved. I would find out what codes the ECU is sending out. I would take apart each connection and clean them then reconnect them. Do you know if your ECU is the original style metal box or the newer plastic one? If the O2 sensor is bad you will get a code from the MIL. If there aren't any codes displayed then you may have a vacumn leak. More than likely any problem you have related to an EFI motor is generally a bad connection or one of the sensors is bad. If one of the sensors are bad then the engine goes into open loop which makes the engine run rich. It is my guess that running rich is a safety parameter. Running rich will cause the engine to run bad, running to lean will cause the engine to also run poor but could also burn a hole in your piston.


  6. OzburnM

    OzburnM LawnSite Member
    Messages: 1

    How do I get a list of the codes for this mower.

  7. eXmark

    eXmark Manufacturer / Sponsor
    Messages: 4,258


    The codes really won't do you any good w/out the complete service manual (probably more harm than good). Keep in mind, the code doesn't necessarily tell you what's wrong, it basically just tells you where the ECU is getting a bad reading from according to the mapping.

    The vast majority of the EFI problems have been poor grounding. One ground that is often overlooked is there is a single black wire that should go up to the heat shield on the LH side of the engine. We've seen some of those loose or corroded, and have also seen that ground mounted to the blower housing which can cause a poor ground.

    I hope this helps. If you have any questions, don't hesitate to contact us again.


  8. pugs

    pugs LawnSite Gold Member
    Messages: 3,025


    You can get a service manual for the CH or CV engine you have. Section 5 in either manual should have all the info on the EFI System.
  9. Lawn Tek

    Lawn Tek LawnSite Senior Member
    from u s a
    Messages: 457

    Save your self a ton of agrivation and money unplug the oxygen sensor and mow . The dealers will put this and that on it and you will still have problems later .Thats what we did , and we haven't been down since .
  10. pugs

    pugs LawnSite Gold Member
    Messages: 3,025

    Yah, but now you are running in open loop mode which will be richer than needed and consume more fuel than needed. Find someone that knows what they are doing and get it fixed right.

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