M4950 with fuel in crankcase

[paul01]

Hi all.

I'm also a new Aussie member so this is my first post on this forum.

I have a M4950DT with a FEL fitted. The tractor only has 1850 hours on it, which isn't much for a machine of it's age. For some reason diesel fuel is slowly leaking into the crankcase causing the level on the dipstick to rise quite significantly. I'm pretty sure it's diesel because the oil gets quite thin and it smells faintly of fuel.

I recently replaced the diesel lift pump (even though the diaphragm checked out OK) and changed the oil and filter/s. I thought this would fix the problem but after only 10-15 hours use I've noticed that the oil level has risen again slightly.

I'd really appreciate any thoughts or advice on this problem because I'm quite new to diesel engines and the diesel mechanics in my district don't seem to have much experience with Kubotas.

Thanks for the great forum, and for reading my post.

 

[Tx Jim]

Another place for fuel to enter crankcase is the inj. pump. Also does engine run smoothly with no miss or undue smoke?

 

[motorhead]

If they have switched to ultra low sulfur diesel recently in your country, that could be the reason the seals are leaking. I second the injection pump seal leaking.
When we switched (FORCED SWITCH ) to ULSD, many older diesels had problems with seals in the fuel system.

 

[Kubota Newbie]

Either the lift pump or the injector pump, about the only two options.
DO NOT RUN IT LIKE THAT! Too much fuel in the oil will wash the cylinders down and cause ring failure.

 

[motorhead]

Either the lift pump or the injector pump, about the only two options.
DO NOT RUN IT LIKE THAT! Too much fuel in the oil will wash the cylinders down and cause ring failure.

I second this strong opinion too! Best way to destroy piston rings and bore is diluted engine oil with fuel in it.

 

[paul01]

Another place for fuel to enter crankcase is the inj. pump. Also does engine run smoothly with no miss or undue smoke?

Thanks for the reply. Someone did comment that it seems to be blowing more smoke than it should (particularly under load) and that it was missing a bit. What does that indicate?

 

[paul01]

Either the lift pump or the injector pump, about the only two options.
DO NOT RUN IT LIKE THAT! Too much fuel in the oil will wash the cylinders down and cause ring failure.

Sounds serious. I hope I haven't already damaged the cylinders/rings! As I've already replaced the lift pump I guess the injector pump is the next place to look. Any idea what's involved in fixing the injector pump?

 

[paul01]

If they have switched to ultra low sulfur diesel recently in your country, that could be the reason the seals are leaking. I second the injection pump seal leaking.
When we switched (FORCED SWITCH ) to ULSD, many older diesels had problems with seals in the fuel system.

Apparently Australia has had a limit of 10ppm of sulfur in diesel since January 2009. If the pump seals are worn with such low engine hours, the switch to ULSD might explain why!

 

[motorhead]

Thanks for the reply. Someone did comment that it seems to be blowing more smoke than it should (particularly under load) and that it was missing a bit. What does that indicate?

That sounds like a stuck injector or at least one that isn't functioning properly. A bad injector can cause excessive fuel to enter the crankcase. You can isolate the bad injector by loosening the union fitting at the top of the injector, at one time.