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Super-Z Kohler 28efi fuel Delivery problems???

Discussion in 'Mechanic and Repair' started by PEVO, Apr 30, 2012.

  1. 65t

    65t LawnSite Member
    Posts: 60

    True the O2 sensor will not make the fuel pump cycle, but there is nothing in the EFI system that senses fuel pressure. The fuel pump cycling is a function of the ECU programming and calibration. It is just something the ECU does, not in anyway related to fuel rail pressure.
    When replacing the O2 sensor, be sure to check for ANY exhaust leak. Any air (O2) into the exhaust system makes the ECU think the engine is lean, then compensates by adding fuel. It will add fuel to the point of an additional 25% over base calibration, then sets code 34.
  2. 65t

    65t LawnSite Member
    Posts: 60

    Try disconnecting the battery for 5 minutes (clearing ECU) and disconnecting the O2 sensor, leaving it unhooked, and running it. If it keeps running good, it will be O2 sensor related. You will probably get a code from the O2 sensor being unhooked, but it should still run OK. If it goes back to running bad, then it's a problem somewhere else in the system.
  3. Sharpcut 1

    Sharpcut 1 LawnSite Senior Member
    Posts: 450

    Are you using the METAL EFI fuel filter, and when was the last time it was changed?? Release the pressure on fuel rail, and pull filter, see if you are getting fuel through the filter. Kick guel pump over by turning key and priming pump, but be careful as you are going to have 50 psi going through the line. I think you may have a blockage on your fuel filter.
  4. PEVO

    PEVO LawnSite Member
    Posts: 211

    Brand new EFI fuel filter (less than 3-4 hours on it) but if i'm pumping crap from the bottom of one or both tanks it could be that it's already clogged ???
  5. PEVO

    PEVO LawnSite Member
    Posts: 211

    I wondered what controlled the rail pressure (guess thats the reason for the bypass fuel return) anyways i'm still setting off code 31. I'm going to take time to remove both tanks & see what comes out of them...then check the lines & then the selector switch itself. I'm even going to reverse the fuel filter & see if any crap blows out of it even thou it's new. Could it be the new ethanol mix in the gas maybe eating away at the lines inside out?

    To date i replaced

    Fuel pump
    Fuel filter
    Spark plugs
    O2 sensor
  6. mtmower

    mtmower LawnSite Bronze Member
    Posts: 1,115

    Haven't changed my filter yet. Make sure you put it on right. I think it has directional flow. If installed backward may cause problems.

    This is real shot in the dark, but I was in automotive service line for 17 years and we had a vehicle that displayed similar problems. The guys beat their heads for close to two weeks until they found the problem. When the last fuel filter had been installed the nipple of the filter must have been sharp enough or forced on to fast and it cut a sliver of rubber from the inside diameter of the hose. This was on the engine side of the filter. This little flap of rubber acted like a blockage to fuel leaving the filter and restricted it so much it was throwing codes and running poorly.
  7. Snyder's Lawn Inc

    Snyder's Lawn Inc LawnSite Platinum Member
    Posts: 4,541

    I have a 26 efi acting like a coil pack I found problem being in the rail before the bleeder one side was getting fuel other side maybe halfto no fuel ran like a coil pack was going off and on
    the rubber line after the filter and before the rail was falling apart inside was a chunk of rubber stuck just before the bleeder
  8. Sharpcut 1

    Sharpcut 1 LawnSite Senior Member
    Posts: 450

    Seen the ethanol eating the fuel lines from the inside and you find little rubber balls, look like real small ball bearings, in the lines. Sometimes partially clog it, sometimes they get dislodged, it will tun good for a while, then act up. I mentioned the filter because they could of deposited back in the filter and the higher psi are dislodging them.
  9. PEVO

    PEVO LawnSite Member
    Posts: 211

    UPDATE: Went ahead & pulled both tanks, flushed em out...some trash came out of one that i could see, the other looked clean. However when i removed the fuel lines i found some black bits of rubber in them, some bigger than others. Nothing thou was found in the high pressure side of the fuel system. Blew out the selector valve (not clogged but made sure anyway) I went ahead & replaced all the low pressure side of the fuel lines. Mowed for 3+ hours & it didn't act up at all. Hopefully that fixed it!
  10. milo

    milo LawnSite Bronze Member
    Posts: 1,259

    anyone know how to read engine codes on 28efi kohler???

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