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Discussion Starter #1
On our farm we have acquired another jd 6420. The tractor does have some issues but the main one is ( and Ile try to describe it the best I can). The tractor will not start unless the throttle is all the way open. Once started the tractor will sometimes limit the rims to 1100 rpm. No matter how far the throttle is pushed. In order to get it to rev past it must be shut dodown and restarted and then it will rev past 1100. And also after running for a while and you shut it down the machine will not start until the engine has cooled down. The warning light is displayed along with the red light . Any help will be appreciated as we have been told that it is a fuel moisture sensor, and also as simple as a fuse
 

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Has the tractor set any codes?

Since you say "another 6420" if you have another, try swapping batteries. My 6415 did strange electrical things when the battery was going bad. New battery cured my electrical gremlins
 
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Discussion Starter #4
No on the codes we did put new batteries all filters to and it still is doing it. I just don't understand how the suspected fuel moisture sensor that we were told to check would make the machine not start after it's ran for twenty mins. The other machine has been good to us other than a flat tire
 

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When light #4 is on, it means there is an engine code active. If it doesn't display on the dash, you may need to get a dealer to plug into it to find out what it is. There are many things that can cause it besides the water in fuel sensor. There is also at least 3 different fuel systems that could be on the 6420 depending on transmission option and serial number range. If you can post a picture of the fuel injection pump, that would help identify which system you have and what possible problems you might look for. Knowing what code is in it would be the most helpful.
 

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Discussion Starter #7
Sure thing I will get a photo later today. I did notice the tractor does have a fuel leak somewhere as I looked under it and there is fuel on the underside
 

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Thanks for the pics. You have the Stanadyne DE10 fuel system. A few things I noticed in the pics. First, the wetness you see is probably the rubber fuel lines dry rotted and seeping. This can be causing problems. I would recommend replacing all the rubber lines from the tank, to the fuel filters, transfer pump and injection pump. The electric fuel pump should be mounted inside the frame rail under the filters. If that pump has been changed in the last few years it is a higher flow pump and fuel lines should have been reworked at that time to bleed off some of the fuel to prevent excess pressure being delivered to the injection pump. If someone did not follow instructions and connected the new pump with old hose routing, that also can cause erratic running issues and even injection pump damage from the excess pressure. (if transfer pump has plastic fittings snapped on each endand wires attache to pump with nuts, it is the newer pump and I can send instructions of required hose routing)In the photo of the filter with glass bowl on the bottom, I can see a wire connector under it that is not connected. If I am not mistaken, that is the connector for the water-in-fuel sensor which should be screwed in the bottom of the glass bowl. If it is not connected, it can cause the engine code light. Lastly, the wire connector plugged into the injection pump farthest to the rear appears to have tape around the wires. The circuit is very sensitive to any resistance and can cause shutting down or erratic running. I would disconnect the wire and check the pins in connection to be sure they are clean and if there are any splices in the wires under the tape, be sure the splices are clean and tight.
 

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Is there a recommended brand fuel line? The lines on my 6415 are starting to leak at the clamps. They have a cloth braid on them. That seems kind of old school to me :dunno::dunno:

Was there an electric pump update for the 6415 that needs to be done? Mines a 2006
 
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For What Ever It is Worth

I have a 6420 that all the lines started to bleed through so I went the local Auto Parts Store and got the Rubber like Diesel fuel lines and replaced all these bad boys. Life returned to normal again!
 

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Discussion Starter #13
Starting to look at the machine now, I looked on the bottom of the filter and there is no place for the connection to screw in. Anyone with advise please help!
 

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Is there a recommended brand fuel line? The lines on my 6415 are starting to leak at the clamps. They have a cloth braid on them. That seems kind of old school to me :dunno::dunno:

Was there an electric pump update for the 6415 that needs to be done? Mines a 2006
I have been using Deere part #M175326 with good results. It is used on current 5M series tractors. It is not the cloth braided style. It is slightly larger OD so the original spring clamps won't work. The cloth braided line seems to have a short lifespan. See failures at around three years.

If your 6415 has the Tier 2 engine, then you have the transfer pump in the frame. The original pumps seemed to work ok, so I am not sure why the replacement pump is upgraded. Just be sure to follow the instructions in the kit when the time comes to replace it. I see no reason to replace it until it fails.
 
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