640 fuel shut off

MI-Bill

Member
My shtnoff on the bottom of the tank has started leaking around the shaft. A lot when open and a little when closed. when using the tractor, the vibration will slowly close it unless it is fully open against the stop. I do not see a way of tightening a nut or anything. The shop is full and I really dont have the time right now to pull the tank. Is it possible to remove the shut off while the tractor is together. It looks like there may not be enough space under the tank to get it out???
 
You most likely have the screw type shut off valve. There is an O-ring that seals the screw which can be replaced. There is a rivet/pin that holds the screw in and prevents it from being screwed out. This can be removed by using a knife blade and carefully prying it up and out. Retain the pin so you can measure the length. The screw and O-ring can then be removed. You can then CAREFULLY tap the hole and use a screw of equal length to the pin as a replacement.(If I recall correctly I used a #10) Find a Viton O-ring as they resist fuel damage. The shut off valve can be removed with the tank on, however there is, as you noted, limited space. If you have small hands it's a great benefit here. If you have a loader it will be more difficult because access is limited. You can search the archives for threads concerning this issue. I rebuilt my shut-off valve and have had not issues leaking. What can occur is that the seat where the screw meets the valve body and the screw tip can become corroded and rough not allowing a proper seal. A little effort polishing the screw end and seat can help. Hope this is of help to you.
 
Yes, the fuel shutoff valve can be removed and replaced without removing the sheet metal and tank.

You will need the right tools, and it helps if your hands are not too large but it can be done.

I've done it so often that I spend more time removing and replacing the fuel than removing and replacing the valve.

Be careful as you will loose some fuel.

Dean
 
Put an inline shutoff so you dont have to use that one anymore. The aftermarket I have used start leaking pretty quick and you can tell they are sloppy.
 
Removing the rocker arm cover will buy more room but doing so is not necessary to R & R the fuel shutoff valve.

Dean
 
(quoted from post at 18:55:12 12/19/17) Removing the rocker arm cover will buy more room but doing so is not necessary to R & R the fuel shutoff valve.

Dean

It sure does help. I think that it is one of those things where the job takes longer when you try to make it shorter by doing less, but then that less takes more time, just because of being awkward. I know that I have wasted plenty of time in my life by thinking that I can do it with what is in my tool box instead of taking the time to go out to my truck and get the right tool.
 

I have got them out with out removing a thang luck I guess I found I can take the rear and front of the hood loose lift it and jam a few wood blocks tween the tank and valve cover and get the valve removed and installed EZ... Maybe I took a few more bolts loose but it was EZ...
 
I've changed so many of them that I can do it in about 30 minutes plus about another 30 minutes to R & R the fuel.

That said, I work only on my own tractors, know exactly what I need and have the right tools on hand. It does help if your hands are not too large.

Dean
 
It will come out no problem. Having enough room to swing a wrench can be difficult, though. If you find it difficult to remove and replace the fuel line, removing the manifold will give you lots of room.
 
(quoted from post at 21:23:50 12/19/17) I've changed so many of them that I can do it in about 30 minutes plus about another 30 minutes to R & R the fuel.

That said, I work only on my own tractors, know exactly what I need and have the right tools on hand. It does help if your hands are not too large.

Dean

I have trouble finding winter gloves. My fingers are too fat for fingers of the right length so I have to wear XLs which leave a half inch of cold air beyond the tips.
 

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