John Deere 6420 fuel problems

robert clarke · Jul 14, 2012

Just noticed the diagrams in this site after I entered the posting. Look at the diagrams and you will see the flow restrictor valve that I was talking about. It is #6. One end is completely open but the other end is closed off with a smaller hole drilled in it, to reduce the flow getting back to the return line and on into the fuel tank. Also I got the prices reversed for the one way valve and the flow restictor valve. One way valve $29.95 CAN. and flow restictor valve $4.50 CAN. If you want to see if that line letting fuel get back to the return line and to the fuel tank is the problem, before making any investment in parts, - just use your vise grips and clamp that line closed so nothing, or very little fuel can get back to fuel tank, - and run electic fuel pump for a minute or two before starting engine. If the engine runs properly then you just proved to yourself that you need that part #6 - the flow restictor valve. I just think the one way flow valve is also a good idea for all it costs.

robert clarke · Jul 14, 2012

Also see my 2nd reply at bottom right as part 2 of 2. My tractor has 2 fuel filters and an eletric fuel pump between the frame and the motor. I have pulled the fuel gage out of the fuel tank and there is no lift pump on that assembly. That is why I think it is a good idea to have a one way flow valve in the line. Would likely be best at the bottom of draw line in the fuel tank - sort of like a foot valve at the bottom of a water well. It stops any fuel from draining back down into the tank and always keeps the fuel lines full. I put my one way valve in the draw line, as I said earlier, up by the back of the engine where the line comes out from under the cab,and from the top of the fuel tank. It is easy to do at that point and works just fine. You must make sure that you do this on the line that goes down to the end of the electric fuel pump (closest to the cab). That is the draw end of the pump. The hose coming up from the other end of the pump - toward the front end of the engine, is the pressure side and goes up to the fuel filters. If you lift the thick floor mat in the cab ( clutch side) and lift the plastic piece (about 5" by 6") you will be looking down on top of the fuel unit on the top of the fuel tank. There are two metal pieces where the rubber fuel lines connect on to.They will be pointing toward the front of the tractor. The one closest to the steps (clutch side) is the draw line going to the fuel pump. Make sure you follow this line right out from under the cab to the fuel pump (the two lines can be crossed under the cab and you would be hooking the wrong line to the fuel punp). This line closest to the step goes down into the tank and has a plastic cage with integral screen at the bottom of the drop tub in the tank. The return line is just a piece of rubber line that drops down to the bottom of the tank. If you take these simple steps I think many people will solve their problems. I think that in many cases, - the engine is not getting enough fuel (sort of like the way it sound when running out of fuel). Not air getting into the system but a FUEL shortage.

MightyReek · Jul 14, 2012

From my experience I wouldn't recommend putting the one-way valve in the suction side of the pump.
Eventually the spring will get rusty (at least around here fuel always gets some residual water) and the ball will get "stuck" with the rust, and the pump won't have enough suction to "unstuck" it...
You might get it to work fine in first times, but you will eventually have problems.
And if you have a leak in the hose ahead of the valve you'll get air inside anyway.

If you want to put the one-way valve I'd recommend put it after the last "T-connection", in the line heading to the final fuel filter. In this fuel system the one-way valve isn't as efficient as in the "pump-in-the-tank" system...

robert clarke · Jul 15, 2012

Undoutedly, having a lift pump in the bottom of the fuel tank would be the best idea. According to the diagrams ( likely JD) on this site, the routing of the fuel lines on my used JD 6420 has been changed - likely when they replaced all the rubber fuel lines. My draw line from the fuel tank goes directly to the electric fuel pump - not to the first fuel filter like in the diagram. I suppose the idea of going from the tank to the first filter, before going to the electric fuel pump, would be to save the fuel pump from getting any wear from dirt particles. Other than that, my system works just the same. When people decide to replace all the rubber fuel lines, - probably all the lines are just cut out and thrown away as one unit. It would be easy to not realize that there was a flow restrictor valve in the system, as is shown in the JD parts diagrams, and thus the start of the engine running rough problems. The JD diagrams on this site show a one way valve (part # 45) in the system, ( as they obviosly come out of the factory), so it is conciderd a neccesary part. That diagram shows the one way valve as being between the fuel tank and the first filter. If you put that valve between the first and second filter, then you are leaving a lot of the fuel system with no protection against back draining back into the fuel tank, - and if that part of the system develops a problem, then you could be right back to the same old problem of a rough running engine. If the one way valve is getting to the point of ceasing up, - it may work a little longer on the pressure side of the electric fuel pump, - but that is likely only a matter of time before it causes the same problem anyway. You may be right about the one way valve ceasing up in the future, but if that happens, - then it is easy to put another new one in the fuel line. The real point is that JD shows a one way valve as part of their system, - so that is likely the lesser of two evils.

PhillipD24 · Aug 21, 2012

Well I gave up and called the dealer, They replaced the injector pump and is running fine so far. Haven't got the bill yet but rebuilt pump quoted at about $1700.00. Thanks for you help and advice.