JD 425 Flooding Problem
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Thread: JD 425 Flooding Problem

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    JD 425 Flooding Problem

    This is my first time on here, so I don't exactly know how to post so here goes.

    My JD-425 has a flooding problem. Sometimes it runs ok, and sometimes not. When I turn on the ignition, the fuel pump starts (as normal) and I can usually start it. Then, after running for a while, it begins flooding. This is between 15 minutes and half an hour most of the time. I can keep it running if I go full throttle and have the tractor under load, like mowing grass, but there is so much gas entering the carb that there is a bit of black smoke as well.

    If I stop it and remove the air cleaner, and look into the carb, there is gas everywhere.

    Here is what I did so far...

    The carb was new 3 years ago. But I removed it, and took it apart (did this 3 times). Each time I took it apart and put it back together, I know I did it right because the machine started and ran as noted above. I thought it just might be plugged or something. The first time I took it apart I also replaced the electric solenoid valve, just to be sure. And I know it works, because I saw it operating with the carb disassembled. Then, I thought it might be that the float valve was leaking or perhaps the floats had a hole and was full of gas. All was good. When the carb was back together, I blew into the fuel hose when the carb was full of gas and proved that the float valve was working. Hmmm. There is a manual in-line fuel shutoff valve, so what I did was throttle it back so that it would take 30 seconds to to let about an ounce of fuel out. Full blast, the pump actually pumps a lot of fuel. This time, I was able to keep the machine from flooding too bad. And was able to mow the 1 acre of grass I have. Today, however was different. It ran for about 5 minutes, then began to act up. I turned it off, removed the air cleaner and looked into the carb. When I turn the ignition switch on, (not engaging the starter) I can see tons of gas coming out of every carb orifice, flooding into the engine, gas everywhere! This is without the engine running! The only thing I can come up with is that the fuel pump for some unknown reason has too much pressure behind it and is causing the float valve to not shut.

    Another wierd thing is that when I turn a sharp corner, under the flooding condition, the flooding gets noticably worse.

    Any ideas anyone? Is there a pressure regulator somewhere in the fuel pump line?


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    SulleyBear's Avatar
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    Welcome to the thread.

    First, it sounds like the float level is set too high, allowing too much gasoline into the carb.

    The needle and seat in these machines are very negatively affected by the fuel now sold at the gas pumps which has Ethanol Fuel blended in it. The ethanol will crystallize and turn almost sugar like inside the fuel system components and not permit the needle valve to full close in the seat, which means more fuel than you need and fuel continuing to flow.

    The fuel pump pumps a static amount of gasoline, when its running. Your system does use a control valve, shown as number 11 in the illustration. Make sure this valve is functioning and isn't plugged open. You may want to ask your dealer if this is a commonly replaced item and if it is, replace it if you aren't 100 sure its working correctly.

    I would make sure the float level is set correctly. With the carb being 3 years old, I would replace the needle and seat with a good quality part. Unless you inspect it with a magnifying glass, you might not see the issues which are impacting the needle valve and the seat. 3 years of use with ethanol fuel is a LONG TIME.

    Once you get the issue resolved, I would make it a practice to shut the fuel shut off valve and allow the tractor to run itself out of gas if you are going to be not using the tractor for more than a couple of weeks. This will run all of the gas out of the carb and help to reduce the ethanol problems in the fuel system. Plus this will keep the valve freely operating.

    Your float level is likely too high, allowing too much fuel flow. The difference could be as small as a few thousandths of an inch. Between installing a new needle and seat ( BOTH PIECES) and setting the float level, this is where I would begin.

    Also, there are different carbs used on the 425 so make sure to take your tractors serial number and the carb for the specific markings to make sure you get the right parts you need. This is very important......

    I would purchase a new float and needle and seat and gasket set just to be safe. You can use the old float, but if it were mine, I would replace the needle and seat and float just to be safe. In this illustration it is the kit shown as number 8 but I would make sure you get the right parts based upon the serial number and the carb numbers.

    Check out this link for the differences. Go down to the carbs and you will see the different series numbers.

    John Deere - Parts Catalog

    Please post a follow up with what you find......Thanks

    Last edited by SulleyBear; 06-05-2018 at 08:33 AM. Reason: correction based upon model diff
    Fozsey likes this.

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    Fozsey's Avatar
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    I think Sully meant number 10 and that's a shutoff valve. If you are flooding, your needle valve isn't functioning correctly either due to debris or improper adjustment.


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