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RonP
12-23-2007 22:41:54
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Re: fuel pump leak in MF275 - FIXED in reply to RonP, 12-12-2007 07:49:13
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Thanks to instructions and encouragement from this site (TomTex, DavidP, and others) I recently fixed the leak on my MF 275 fuel pump. Here are some thoughts/descriptions to add to what's already been posted on that procedure.
The pump was leaking at the shut-off shaft, which for this CAV pump was the front shaft. I got a rebuild kit for $17.11 from J.G. Parks diesel repair. The kit was made by Delphi and contained many more replacement parts then what I used. First, shut off the fuel supply using the valve up by the fuel tank. Be sure the fuel pump is clean so no dirt gets into it when the cover is off. There should be a metal tag attached to the side/bottom of the pump housing. I used steel wool to clean this metal tag until I could read all three sets of numbers. The number I needed to ID the pump type was the top number, the DPA number. Apparently this model of pump is fairly common, since the parts guy said he had 23 of the rebuild kits.
To take off the cover, undo the small nuts on the top of the shut-off and throttle linkages. These small nuts are on the shafts that come out of the top cover on the pump. Under each nut is a small washer. To lift off the shut-off linkage you also have to remove the mounting bracket that holds the shut-off cable in place. The shut-off linkage cable can be curved down and away from the pump and tied down, but the throttle linkage is not very flexible and harder to get out of the way (it can be pushed down next to the outside of the pump housing). Once the shut-off cable and throttle linkage are out of the way, remove the two nuts in the middle of the cover. Be sure you have a really good light source before starting to take off the cover. Gently break the cover free of the gasket and lift the cover up about 3/4 to 1 inch. There is a spring attached to a small triangular piece of metal that is in turn attached to the bottom of the throttle shaft (the shaft on the right). Note which hole the spring is attached to. My piece of metal had three holes in a row, and the spring was attached in the first hole. The other end of the spring was attached to a short pin (with a tiny spring) that went through a rounded piece of metal. This vertical piece of metal is just to the left of center, and mine had three holes in a vertical line. The pin on my 275 was through the middle hole. Note which hole the pin goes through. Now, unhook the spring at one end and take off the cover. I used a clean pair of needle nose pliers and removed the spring where it went through the pin. Once the cover is off look at the bottom of the shut-off shaft and you will see a prong that extends down about 1/4 inch. If you haven't rotated the position of the shut-off shaft while removing the cover this short prong will be toward the back of the cover. Now look in the pump and toward the back you should see the fuel shut-off mechanism. It's a flat piece of metal that extends from the back left (where the shut-off linkage shaft goes down into the pump) almost all the way to the right side of the pump. At the left end of this piece of metal (where the shut-off shaft just came from) you will see a notch facing the back of the pump. This notch has a "U" shape and is where the prong on the shut-off shaft has to fit when you put the cover back on.
Both the throttle shaft and the shut-off shaft come out through the bottom of the cover. My shut-off shaft came out easily because is was already loose and was where the pump was leaking. I had to push on the throttle shaft to get it to come out. Both shafts have two small o-rings. Once the shafts were out, I removed the old o-rings with a small screwdriver. To put on each new ring, I coated it with vaseline, pushed it onto the rectangular top of the shafts, and then used a small screwdriver to work it down over the shoulder and onto the shaft. Then by using your fingers you can push the o-ring down into the grooves on the shaft. Once the o-rings have been replaced, push and twist the two shafts back into the cover. You want the short prong on the shut-off shaft to be rotated toward the back of the cover.
Remove the old gasket from the pump housing and wipe off the metal where the new gasket will go. There were two "teeth" or projections on my gasket which fit into slots in the front and back. You'll see from the old gasket how the new one has to be placed.
To replace the cover I used a pair of needle nose pliers to fit the end of the spring through the small hole in the end of the pin. Then as you lower the cover you have to make sure the prong at the bottom of the shut-off shaft goes into the notch on the shut-off mechanism. You can just barely see where it is as the cover goes down. If the prong doesn't fit into the notch, the shut-off valve won't work. This is what happened the first time I replaced the cover. The tractor started right up (no air bleeding of the pump or lines was needed) and I thought I was done. But when I tried to used the shut-off switch nothing happened, and when I manually used a pair of pliers to turn the shut-off shaft nothing happened. So I put the tractor in high gear and popped the clutch to make it cut off. Then the next time I replaced the cover I was very careful to be sure the shut-off shaft end fit into the notch on the sliding piece of metal that causes the fuel flow to stop. Finally I just snugged the two nuts down on the cover and reattached the linkages to the two shafts. When I turned the fuel back on the tractor started fine and the pump doesn't leak.
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