Oil & Fuel diesel in oil

[rj's barn]

Hello all. I have a real booger on my hands. Maybe some of you would be kind enough to lend me some of your sage like wisdom. I have a mistu 2350 that ran like a champ until now. I am getting diesel in my oil, at an alarming rate, about a quart per 3 hours of operation. I know the fuel pump housing is cast in such a manner that exposes the pump assembly to the crank case. But it has plenty of power and still runs like a striped ape and doesnt seem to be losing fuel pressure. I thought it might be a washed out cylinder but im not getting very much blow by out of my crank case vent on the valve cover. It doesnt seem to be a stuck injector because its not smoking or missing under load or at high idle and it doesnt seem to raise the oil level when it is at rest with the engine off. I'm stumped. help?

 

[DieselPower]

I don't have any first hand experience with that engine but it is not uncommon for a injection pump to leak fuel into the lubricating oil system. It's probably a bad seal in the pump. What kind of lift pump does it have. Depending on how the lift pump is mounted to the engine it could also be leaking into the crankcase. If it's running fine and not smoking like a freight train then it's most likely not a cylinder issue.

 

[rj's barn]

This machine doesnt have a lift pump. The fuel tank sits above the fuel pump inlet and uses gravity to get fuel to the injection pump. I did find one "minor" problem. The filter in the fuel bowl is a half inch too short for the bowl. I have had that filter in operation for the 127 hours I have put on the machine. Not a drop if diesel has been filtered since it was "reconditioned"..... somewhere. Could unfiltered diesel lead to this kind of problem?

 

[DieselPower]

I guess it's possible if enough contaminates got into the pump and abraded the shaft/seal. I would think it would have damaged a injector before that though.

 

[rj's barn]

So the fuel pump could have an internal leak into the crankcase and not reduce injection pressure to a noticeable degree? Or at least not enough of a decrease that would affect the pop off pressure of the injectors?

 

[DieselPower]

Like I said, I am not familiar with your engine but many injection pumps are oil lubricated in a portion of the pump. If the seal between the fuel and oil sides of the pump leaks the fluids can get past the seal.

 

[rj's barn]

Appreciate the guiding light fellers. Took the injection pump to a rebuilder and it is leaking around the plungers and sleeves. At any rate i should be back in the field in a week or so. Gracias!