I wanted to share my experience with replacing the fuel filter on my recently acquired 2008 Kubota L3240 with 850 hours on it.
Knowing that air in a diesel fuel injection system is a bad thing, I had searched the forum and elsewhere online for any tips or tricks on getting the air out of the fuel delivery system after removing and replacing the fuel filter bowl. I had seen several instances reported where they had a no start condition after filter replacement and bleeding, and I wanted to avoid that, so I followed the instructions in the manual, or so I thought.
The manual says to fill the fuel tank during the process. I only had 5 gallons of diesel on hand and put that in the tank which brought the level up to about half a tank. I thought surely that is enough. It wasn't.
After replacing the filter and bowl, opening the fuel petcock, and watching the fuel fill the bowl, I then opened the fuel bleed valve on the fuel injection pump inlet. I then started the engine and it started up just fine and I ran it for 15 or 20 seconds. I then shut it down and closed the fuel bleed valve per the manual. I then got back on the seat to start the engine and move the tractor out of my shop when it started then sputtered and died.
Several start attempts resulted in the engine trying to start and then die. It was getting late in the evening and I decided to call it a day and do some more online research before continuing, plus the battery was getting low and I put it on the battery charger.
I went back over the instructions in the manual and the only thing I didn't satisfy was the "full" fuel tank. The next day I went to town and got some more diesel and also picked up some new fuel filter o-rings as the ones on my ~15 year old tractor were hardened and had taken a set.
I then topped off the fuel in the tank to the bottom of the filler neck, which turned out to be just a little bit too much fuel. When I closed the fuel petcock on the filter bowl and removed the bowl, the fuel flow didn't completely cease. The top of the fuel filter bowl housing has a vent line directly to the top of the fuel tank and I had filled the tank slightly above this vent line port in the tank, so I ended up letting about a quart of fuel drain out of this vent line into my catch pan before changing the o-ring inside the filter housing. Note that this vent line also negates the need to leave the fuel bowl nut loose when opening the petcock and filling the bowl as it provides an air vent path back to the tank at the top of the filter housing.
Anyway, I had my Mity-Vac vacuum pump and was prepared to pull a vacuum on the fuel delivery bleed valve vent hose in an attempt to pull out any air in the lines between the fuel filter, lift pump, and fuel injection pump inlet, but as soon as I disconnected the rubber line from the #1 fuel injector excess fuel return line, a solid stream of fuel was already flowing out of the hose due to the high level I had in the fuel tank, so I put the hose back on the fuel injector. After tracing all of the fuel return line piping I saw that all fuel injector fuel return lines are connected with each other and another rubber hose on #3 fuel injector going back to another port at the top of the fuel tank. This provides the air vent path for the fuel system provided the fuel level in the tank is high enough to push all of the air out.
I verified the fuel bleed valve was open then I attempted to start the engine with full throttle and it fired up with a little struggle before clearing up and I immediately lowered the throttle to near idle and let it idle for a minute or so, then closed the fuel bleed valve while the engine continued to run. Case closed, end of story.
Another heads up: The fuel filter I removed was a Wix filter. When I installed the new Kubota fuel filter, it didn't fit very tight on the o-ring in the housing. I measured the fuel filter inlets and the Wix filter was 0.010" smaller than the Kubota filter which had compressed the o-ring over time. This was the primary reason for replacing the o-rings.
Knowing that air in a diesel fuel injection system is a bad thing, I had searched the forum and elsewhere online for any tips or tricks on getting the air out of the fuel delivery system after removing and replacing the fuel filter bowl. I had seen several instances reported where they had a no start condition after filter replacement and bleeding, and I wanted to avoid that, so I followed the instructions in the manual, or so I thought.
The manual says to fill the fuel tank during the process. I only had 5 gallons of diesel on hand and put that in the tank which brought the level up to about half a tank. I thought surely that is enough. It wasn't.
After replacing the filter and bowl, opening the fuel petcock, and watching the fuel fill the bowl, I then opened the fuel bleed valve on the fuel injection pump inlet. I then started the engine and it started up just fine and I ran it for 15 or 20 seconds. I then shut it down and closed the fuel bleed valve per the manual. I then got back on the seat to start the engine and move the tractor out of my shop when it started then sputtered and died.
Several start attempts resulted in the engine trying to start and then die. It was getting late in the evening and I decided to call it a day and do some more online research before continuing, plus the battery was getting low and I put it on the battery charger.
I went back over the instructions in the manual and the only thing I didn't satisfy was the "full" fuel tank. The next day I went to town and got some more diesel and also picked up some new fuel filter o-rings as the ones on my ~15 year old tractor were hardened and had taken a set.
I then topped off the fuel in the tank to the bottom of the filler neck, which turned out to be just a little bit too much fuel. When I closed the fuel petcock on the filter bowl and removed the bowl, the fuel flow didn't completely cease. The top of the fuel filter bowl housing has a vent line directly to the top of the fuel tank and I had filled the tank slightly above this vent line port in the tank, so I ended up letting about a quart of fuel drain out of this vent line into my catch pan before changing the o-ring inside the filter housing. Note that this vent line also negates the need to leave the fuel bowl nut loose when opening the petcock and filling the bowl as it provides an air vent path back to the tank at the top of the filter housing.
Anyway, I had my Mity-Vac vacuum pump and was prepared to pull a vacuum on the fuel delivery bleed valve vent hose in an attempt to pull out any air in the lines between the fuel filter, lift pump, and fuel injection pump inlet, but as soon as I disconnected the rubber line from the #1 fuel injector excess fuel return line, a solid stream of fuel was already flowing out of the hose due to the high level I had in the fuel tank, so I put the hose back on the fuel injector. After tracing all of the fuel return line piping I saw that all fuel injector fuel return lines are connected with each other and another rubber hose on #3 fuel injector going back to another port at the top of the fuel tank. This provides the air vent path for the fuel system provided the fuel level in the tank is high enough to push all of the air out.
I verified the fuel bleed valve was open then I attempted to start the engine with full throttle and it fired up with a little struggle before clearing up and I immediately lowered the throttle to near idle and let it idle for a minute or so, then closed the fuel bleed valve while the engine continued to run. Case closed, end of story.
Another heads up: The fuel filter I removed was a Wix filter. When I installed the new Kubota fuel filter, it didn't fit very tight on the o-ring in the housing. I measured the fuel filter inlets and the Wix filter was 0.010" smaller than the Kubota filter which had compressed the o-ring over time. This was the primary reason for replacing the o-rings.
