Go Bottomdiesel injector pump
 | Chris Dehnert
Join Date: Posts: 1 
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2003-06-07 57048
I have a 2850 28 hp Kubota tractor. When it has been run hard for an hour or so and is hot, the engine power drops off (almost stalling) and developes a terrible skip. When the tractor cools down it runs fine again. The fuel filter has been changed, the gas cap is vented OK. The tractor has not been run out of fuel. Suspecting a temperature related problem with the injector pump, I ran cold water over the pump when the problem developed (while the tractor was running) and the problem completely dissapeared. When I continued to run the tractor, the problem came back again in about 10-15 minutes as the pump heated up again. I repeated this 3 times with exactly the same result.
Does anyone know what could be happening with this pump? Could be cracked or have a bad seal? Can it be rebuilt?
thank you.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2003-06-08 57080
Many tractors have a fuel screen in the tank or on top of the shut-off valve and that would be a good thing to check. Hydraulic oil can overheat from pump cavitation due to obstructed suction lines. However, hydraulic oil is re-circulated and that idea seems a stretch to apply to an injector pump.
It might be good to sort out if the problem is related to high rpm, high throttle or both. Working a tractor hard probably means both. I suppose that something like a bad seal could bind a shaft and produce more heat at higher rpms. High throttle positions wouldn't increase the motion in most pumps at given rpm's but the pump would be working against pressure over a longer duration. I suppose scoring in the pump barrels could produce more heat at higher throttles. It also would be good to ensure that the engine is operating within a normal temperature range.
Off the top of my head, you might try a fuel additive with a pump lubricant if one isn't already used. I don't know how old the pump is but it might be engineered for higher sulfur fuel--I'm aware that's another stretch. Since I seem to be into stretches, It might be good to think about whether an obstructed return line from the injectors to the fuel tank could heat the pump.
Pump work is pretty specialized and I most pumps are replaceable as a unit. My Ford parts manual doesn't list part numbers for internal parts but rebuilds may be available through a dealer.
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 | harvey
Join Date: Sep 2000 Posts: 1550 Moravia, NY 
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2003-06-08 57085
How many hours is on it???? It sounds like a fuel starvation problem. What condition are the lines in? Bends or kinks? Rubber sections are fuel rated and not comming apart inside?
CHECK ALL OF THE CHEAP AND EASY TO FIX FIRST!
Are you pouring water on the injector pump while it is skipping and hard at work. Or did it get a chance to rest a little while you got the water?
If it is the injector pump I suspect you would have a problem across the board with it. But strange things do happen. Unless you have something very weird I would not support vapor lock theory.
Does this model have a fuel pump seperate from the injector pump? Or is it buitl in?
Also to buy into Tom are you sure it is a good grade of fuel?
Harvey ....
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| Chris Dehnert
Join Date: Posts: 1
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2003-06-09 57236
The tractor has 2600 hours on it. It does not have a fuel pump, the fuel tank is mounted on top of the engine. I'm sure the fuel is good grade---I purchased it from a truck stop at which the move a lot of fuel. I have added a fuel lubricant.
Your suggestions about replacing the rubber fuel lines is good. I will try that. Perhaps they are collapsing when the tractor gets hot.
I'll keep you posted. ....
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 | Art White
Join Date: Jan 2000 Posts: 6898 Waterville New York
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2003-06-10 57253
Chris check your fuel return lines first. ....
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