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  1. #1
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    Default John Deere 6420 fuel problems

    I have a JD 6420 that started running rough replaced both fuel filters. Noticed that fuel does not come out bleeder on filter nearest the cab. Checked fuel pump and it appears to be working good. Can work with filters ie refilling filters and working with bleeder to get air out and tractor will start and run perfect all day long after sitting over night same problem. Have problem with fuel gauge not registering correctly (showing empty) then it goes back to working. Got fuel sensor switch code yesterday and gauge for water in bowl, blinks when running rough. have check fuel lines can't find any leaks, acts like it getting air some where. Anybody have any ideas? What happened to the good ole days before computers.

  2. #2
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    Default Re: John Deere 6420 fuel problems

    NEVER open the filter near the cabin, it would only suck air into it because the pump is ahead of it, sucking...
    To bleed open the front filter, choose the screw that has an arrow pointing out of the filter.

    If you have a leak in the "suction side" of the pump you won't notice it, and over night you'll have air in the system.

    Many times, the fuel line that connects the tank to the first filter has a leak provoked by the wider part of the fitter (if you open the hose with your knife you'll notice something like a needle hole). Have that fuel line replaced and also the one that connects that first filter to the pump.

    Anyway, if the "engine controller bulb" is flashing you MUST check the diagnostic codes in the ECU. You may have some other problem with the injection pump in the worst scenario...

    If you find the problem, please come back with the answer, people always likes to know.
    Good luck

  3. #3
    Elite Member JasG's Avatar
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    Default Re: John Deere 6420 fuel problems

    Quote Originally Posted by MightyReek View Post
    NEVER open the filter near the cabin, it would only suck air into it because the pump is ahead of it, sucking...
    To bleed open the front filter, choose the screw that has an arrow pointing out of the filter.

    If you have a leak in the "suction side" of the pump you won't notice it, and over night you'll have air in the system.

    Many times, the fuel line that connects the tank to the first filter has a leak provoked by the wider part of the fitter (if you open the hose with your knife you'll notice something like a needle hole). Have that fuel line replaced and also the one that connects that first filter to the pump.

    Anyway, if the "engine controller bulb" is flashing you MUST check the diagnostic codes in the ECU. You may have some other problem with the injection pump in the worst scenario...

    If you find the problem, please come back with the answer, people always likes to know.
    Good luck
    This tractor should have a lift pump in the tank that pushes fuel through the filters to the injection pump. With the key in the run position engine off he should be able to open the bleed screws on either filter housing, one at a time and bleed air out.
    “Government is like a baby. An alimentary canal with a big appetite at one end and no sense of responsibility at the other."


    Ronald Reagan

  4. #4
    Elite Member JasG's Avatar
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    Default Re: John Deere 6420 fuel problems

    Quote Originally Posted by PhillipD24 View Post
    I have a JD 6420 that started running rough replaced both fuel filters. Noticed that fuel does not come out bleeder on filter nearest the cab. Checked fuel pump and it appears to be working good. Can work with filters ie refilling filters and working with bleeder to get air out and tractor will start and run perfect all day long after sitting over night same problem. Have problem with fuel gauge not registering correctly (showing empty) then it goes back to working. Got fuel sensor switch code yesterday and gauge for water in bowl, blinks when running rough. have check fuel lines can't find any leaks, acts like it getting air some where. Anybody have any ideas? What happened to the good ole days before computers.
    There should be fuel coming from the bleed screw with the key on. Did you try removing the screw to see if some how it is plugged? I would replace the fuel lines and also we added a check valve that the tractor did not come with about 6" from the filter, between the filter and the tank. Ours is a different model tractor, but should be similar on fuel delivery as far as I can tell. Ours had similar symptoms, fuel line was bad, but not leaking enough that we could tell till we cut the outer cover off. At the time re replaced the line, the dealer said we should add the check and we did. Hopefully that is all it is.

    Can't help you with the fuel guage though.
    “Government is like a baby. An alimentary canal with a big appetite at one end and no sense of responsibility at the other."


    Ronald Reagan

  5. #5
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    Default Re: John Deere 6420 fuel problems

    Quote Originally Posted by JasG View Post
    This tractor should have a lift pump in the tank that pushes fuel through the filters to the injection pump. With the key in the run position engine off he should be able to open the bleed screws on either filter housing, one at a time and bleed air out.
    With two fuel filters there is no lift pump inside the tank but a transfer pump attached to a plate between the chassis and the engine block.
    Like this:

  6. #6
    Elite Member JasG's Avatar
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    Default Re: John Deere 6420 fuel problems

    Quote Originally Posted by MightyReek View Post
    With two fuel filters there is no lift pump inside the tank but a transfer pump attached to a plate between the chassis and the engine block.
    Like this:
    If that is the case, then how do you bleed the system?

    The manual I looked at just says the system could have 1 filter or 2 filters and does not say there is a difference. The tractor I work on has just 1 filter with an in tank pump.
    “Government is like a baby. An alimentary canal with a big appetite at one end and no sense of responsibility at the other."


    Ronald Reagan

  7. #7
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    Default Re: John Deere 6420 fuel problems

    Quote Originally Posted by JasG View Post
    If that is the case, then how do you bleed the system?
    Open the "fuel exit" in the front filter.
    The filter support has 5 connection points.
    The usual bleeder is connected to pump's return.
    Then you have two entrances, one is connected to the transfer pump, the second is blocked.
    You have two exits, one is connected to the injection pump and the second is blocked. You remove the screw from this one witch is blocked.
    There are small arrows over these exists/entrances pointing in and out.

    Opening the rear filter would result as pulling the pump out of the tank in your tractor.

  8. #8
    Elite Member JasG's Avatar
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    Default Re: John Deere 6420 fuel problems

    Quote Originally Posted by MightyReek View Post
    Open the "fuel exit" in the front filter.
    The filter support has 5 connection points.
    The usual bleeder is connected to pump's return.
    Then you have two entrances, one is connected to the transfer pump, the second is blocked.
    You have two exits, one is connected to the injection pump and the second is blocked. You remove the screw from this one witch is blocked.
    There are small arrows over these exists/entrances pointing in and out.

    Opening the rear filter would result as pulling the pump out of the tank in your tractor
    .
    With your drawing I can see that.

    I wonder if there is a difference between US and Euopean models? Like I said my manual only states you may have one or 2 filters and it is suppose to cover this model tractor.

    Thanks for the info.
    “Government is like a baby. An alimentary canal with a big appetite at one end and no sense of responsibility at the other."


    Ronald Reagan

  9. #9
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    Default Re: John Deere 6420 fuel problems

    I've check it, if you look in online parts catalogue Section 30 - ENGINE AUXILIARIES, TANK, AIR SYSTEM, page 269 - FUEL HOSES (WITH TIER II ENGINE) there is the same image I put here.
    Offcourse, this is variable according with the injection system in the tractor.
    This is valid for Tier II Injection Systems (HPCR common rail level 11 and Stanadyne DE10 level 12) and Tier 3 (6030 series) both 14 and 16 levels.

    Tier 1 Bosch VP44 level 4 won't have this (has a different transfer pump is mounted on top of filter "head").
    Last edited by MightyReek; 07-10-2012 at 10:17 AM.

  10. #10
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    Default Re: John Deere 6420 fuel problems

    I bought a used JD 6420 and had the same problem. The injector pump had no paint on it - so it had been removed and checked over. The same with injectors and all the fuel lines from the injector pump to the injectors - no paint - so they were checked over also. Also, all the rubber fuel lines had been changed. Like you, I changed the fuel filters and there was no change. The little fuel pump was woking all right. Was looking at this thing and trying to figure out what was the problem, when I noticed that after the fuel line came back up from the little electric fuel pump, there is a tee in the fuel line. This is only about 2 inches above the frame of the tractor. Off of this tee, the line Goes on up to the first fuel filter- about 10 to 12 inches of lift. Now, If you go back down to the tee in that line, you will see that a line goes off the tee and straight level across toward the back of the engine and goes into another tee. That line is the return line to the fuel tank. Much easier for the fuel to just return to the fuel tank than to try and lift up to the fuel filters and go through the filters and injector pump and the rest of the system and then back to the fuel tank. Is that line below the fuel filter at the tee, going over to the return to the fuel tank, necessary. I pinched the line off with a pair vise grips to see if the tractor would run properly. I turned the ignition key to the on position and let the electric fuel pump run for a miniute or so to chase any air out of the system and then started the engine. Tractor ran perfectly, which proved that the engine was not getting enough fuel. After talking to the local JD dealer parts people, I find that the line over to the return is a necessary part of the system - an excess flow line. "BUT" there must be a flow restrictor in that line to limit the amount of fuel that can return to the fuel tank. This forces more fuel up to the fuel filters so the system gets enough fuel to make the engine work properly. You cannot eliminate that line going over to the return to the fuel tank or you may make the little electric fuel pump work too hard. The flow restrictor is about 1.5 inches long and is just like a little piece of copper tubing that you would use to join two pieces of the rubber fuel line. Looks like it is made out of brass. Just cut the fuel and insert the flow control restrictor and a couple of clamps and you should have your problem solved. I also added a one way flow valve into my system as an extra measure. It also goes into the fuel line, between the fuel tank and before the little electric fuel pump. Again, all you do is cut the rubber fuel line and it just inserts into the line like the flow restrictor. This just makes sure that the fuel cannot drain back down into the fuel tank - thus keeping the line always full of fuel. The one way valve was $4.50 CAN. and the flow restrictor was $29.95 CAN. Tractor runs the way it should now. Hope this helps you.

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