Kohler 26 EFI fuel filter cleaning

Discussion in 'Mechanic and Repair' started by hydro_mike, Jul 20, 2007.

  1. hydro_mike

    hydro_mike LawnSite Member
    Messages: 3

    I have a bit of an odd application for a 26hp Kohler EFI that I could use some assistance with.

    The engine is in an amphibious ATV (six wheeler). The engine is a 2000 vintage 24 pin plastic cased ECU. No idea on the hours. I'm guessing under 300. It's clean and was run in the same application flawlessly for a few years. Now that I inherited the engine from a close friend who's machine fell apart around his engine, I'm finally getting my machine built up around the engine. The engine starts and runs great. Good acceleration warming up, but it's running lean after it gets in or near the "closed loop" portion of running. Plugs are reading lean (light brown, but not chalky), and it pops, misfires under load. No black smoke, no buildup on the plugs, etc. If I back off and let it calm down a bit (i.e.- go back to idle). It'll sit and run fine, and will even behave for a few minutes before I decide to get back on it. I'm immediately thinking that fuel pressure is the suspect. I've checked the O2 sensor voltage, and it's grounded very well throughout the chassis reading between 0.2 and 1.0 volts anyplace on the engine/chassis you ground the voltmeter.

    The fuel pump is running fine and recircs well back into the tank. I'm running one in-line filter on the low pressure (pickup) side of the pump, and this pump has the in-pump filter (it's an external pump) that has the 60(?) Micron filter. I made the goof up of momentarily running the pump without the primary filter (on the pickup line), and I think that I may have sucked up some gunk from the tank into the itty-bitty 60 micron filter. I don't have a fuel pressure gauge to check pressure at the rail yet, but if I can't solve it with a couple new filters, I'll need to go that route.

    So, I guess the point of the entire post is this question:

    Can you clean the itty-bitty 60 micron internal filter on the pump with a simple backflush? Please tell me that you don't have to replace the pump. I'm still yet to get home and see if it can be done, but with all the experience here, I wanted to see if someone else had any input. The engine manual doesn't even mention cleaning it, or the need to replace it if it becomes clogged.

    I have a decent amount of experience with small engines, and if this were carbureted, it'd already be fixed. I'm brand new here. Any help is appreciated.

  2. thecrankshaft

    thecrankshaft LawnSite Member
    Messages: 172

    What is the part number of the fuel pump? Only the 24 393 17 pumps have the internal filter. The new 24 393 20 pumps that Kohler uses does not have the filter.

    I strongly recommend Kohler fuel filter 24 050 12-S for before the fuel pump. The metal cased filter is for the high pressure side, after the fuel pump.

    Any check engine lights The EFI engines are very dependent on the 02 sensor and will definitely throw a code if there are intake/exhaust leaks, low fuel pressure, etc. I am not sure how this engine is currently set up, but if you need help, I can tell you how to wire up a check engine light.

    Just remember to check the mechanical condition of the engine before immediately accusing EFI. That is what gives EFI a bad name.
  3. hydro_mike

    hydro_mike LawnSite Member
    Messages: 3

    Thanks Crankshaft-

    I'll check the PN on the pump tonight. Does Kohler really use the metal filter after the fuel pump? I'm assuming it runs between the pump outlet and the engine. 39 PSI is an aweful lot of pressure to hold back. I'll also look up that Kohler number before the pump as well. - thank you!

    Mechanically, the engine seems to be good. I've check for the exhaust leaks, etc. I'm very happy with it's performance up to the point that it misfires. I hope not to join the curmudgeons who belittle the EFI because it's a bit more complex than a two barrel carb.

    Unfortunately, the engine was taken out of a Scag (I THINK) mower before it's application in the ATV, and it's currently missing the MIL (check engine light). I see the service-connect on the wire harness, but I don't have the diagnostic light to plug in to read codes. I have all of the codes and the potential causes sitting in front of me, but w/o the light, they do me no good.

    If you could provide me with the info to hook up the MIL/CEL, I would be indebted. The engine is hooked up only to a centrifugal belt drive clutch (snowmobile or JD Gator style setup), and only sees load when RPMs get above 1800 or so, as the belt engages.

    Again, thank you for the quick response...
  4. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    Cant help much with the technical stuff....never had to deal with that much.....knock-knock!

    But the condition your describing is similar to what happens when I run it out of fuel. It will NOT re-prime itself unless I purge air out at the Schrader valve. It will pop and miss, but usually will idle and continue running. But pop and bang it will. This is the ONLY problem I've had with this engine....And I do not believe there is a cure. So as a word of caution, keep the fuel tank full!

    BTW, my engine runs a BOSCH 0 450 905 002 metal filter after the pump. Only filter prior to the pump is the pickup line.
  5. hydro_mike

    hydro_mike LawnSite Member
    Messages: 3

    Thanks TLS.

    I've successfully purged all the air out of the system. It'll run fine until it warms up, throughout the RPM range. If it starts popping, backfiring I let it go back to idle and it'll be fine.
  6. thecrankshaft

    thecrankshaft LawnSite Member
    Messages: 172

    Maybe I shouldn't phrase it "after the fuel pump". The fuel filter should be between the fuel pressure regulator and the fuel rail on the engine. Fuel flow from the tank to the engine should be:

    Tank>tank pick up>pre-pump filter (Kohler PN above)>fuel pump>fuel regulator>metal fuel filter>fuel rail & injectors

    39 psi pressure is a lot, but it is metal cased and automotive does the same thing. If you have it before the pump, it is most likely causing your fuel starvation problems.

    How did you wire this thing up? There should be a 5 wire connector coming off of the engine that has a purple wire. On a Kohler carburetor engine, this may be confused with the charging wire, but on the EFIs the charging wire should go straight to the starter stud. The purple wire in the harness is from the ECU to blink out codes. Purchase Kohler PN 25 352 19-S and wire it to the purple wire on one side, and the other side should be switched 12 volts from the key switch. Turning the key switch on and off three times makes the ECU blink out the codes.

    It takes a little while to prime, but the air will be purged via the injectors if you run the engine out of fuel.
  7. pugs

    pugs LawnSite Gold Member
    Messages: 3,025

    You may want to be a little more specific about the metal cased fuel filter you are talking about. I have some metal cased ones that are just normal fuel filters...not meant for fuel injection.

    I would say you definitely have to get the MIL hooked up at the very minimum. It would be even better if you could find a dealer with the computer cable...unfortunately I am a little far from you...LOL

    Also as someone else stated I would check fuel pressure at the shrader valve and bleed any air out there. One of my customers had a Toro that was a royal PITA to get running whenever it was run out of fuel. Not sure why. You could cycle the key until the end of time and it would do no good.

    This in an Argo?

    I am attaching a file that is very helpful for hooking up an EFI Kohler. I used it to make a test stand for running the 31 HP Aegis engines. We work on a few of them out of carpet cleaning machines.

    Attached Files:

  8. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    I spend about 30 minutes each time this happens trying to self prime. No way on my setup this is going to happen. A few pushes on the shrader when the pump is pumping (cycles on and off) and its fine.

    Same here. Wonder why some guys have luck, and I repeatedly have been unsuccessful?
  9. pugs

    pugs LawnSite Gold Member
    Messages: 3,025

    Yah, i dunno. I have had no trouble on my engine test stand getting the 31HP Liquid cooled ones to prime themselves. And every time I hook one up its starting with completely dry lines...

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