After my runaway I have installed a 2nd lift pump (first was leaking around bowl seam) and tractor (L3940) is running fine. My problem now is fuel appears to still be getting into the crankcase, even when sitting the level appears to rise. What could be the culprit allowing fuel to get to the crankcase while sitting?
Fuel in the oil
- Thread starter brooster
- Start date
Kubie L3400D
Member
Equipment
L3400DT 4WD, SSQA, Bobcat T190, Flail mower, Brushhog, Brushshark, Ratchet rake
Shouldn't the fuel shut off valve prevent fuel to flow when tractor is off. Or does the fuel shutoff valve go to open after tractor is off?
North Idaho Wolfman
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Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
The main way fuel can get into the oil on these is a bad injection pump, or lift pump.
Don't assume the new lift pump is okay.
If it was sitting on the shelf for a few years (which is quite likely), it may have failed in the first few minutes. The diaphragm gets brittle, you install it and all seems well, but that brittle diaphragm soon cracks and starts pumping fuel into your crankcase.
If it was sitting on the shelf for a few years (which is quite likely), it may have failed in the first few minutes. The diaphragm gets brittle, you install it and all seems well, but that brittle diaphragm soon cracks and starts pumping fuel into your crankcase.
Did you install the stock (Kubota) lift pump? Or, an aftermarket lift pump?
I had an issue with catastrophic leaks of fuel into the crankcase on my Cummins. "Catastrophic", because I could monitor the incident by watching the stripe of fuel being deposited on the roadway in the rear view mirror (escaping from the crankcase vent)!
The issue was that we had installed an aftermarket fuel pump which was pumping WAY more pressure on the outlet side than the injector pump wanted. That pressure pushed the seal out of the driven end of the injector pump, and caused it to pump fuel into the crankcase. Actually happened twice, about a year apart. The last time, it happened when I was in the Harbor Tunnel in Baltimore, and I was forced to drive ~5 miles before I could pull over and stop. Didn't seem to hurt the crankshaft...
Even if you used the stock Kubota lift pump, the improved performance of the new pump over the one you replaced may have overwhelmed tired seals in the injector pump.
My last question is: when was your injector pump rebuilt? WSMs recommend a service interval (including seal replacement, of course) on the injector pump of around 1200 hours, I think.
Before anyone points out that a Cummins motor is not a Kubota motor, they both use Bosch injector pumps, and on both motors, the driven end of the injector pump communicates with the crankcase.
[Maybe a better design would be to have a vent to the outside between two seals on the pump shaft.]
-Paul
The tractor I think is an ‘09 and has just logged 700 hrs. My problems all started when I did the 700 hr service at 680 hrs, after running for about 20-30 minutes the tractor would lose power and I thought the culprit may have been the seafoam I added to the fuel, the more fuel I added and the more I used it the performance improved. And then it ran away on me as I was using it, that’s when I found the crankcase level was overfilled with fuel, vent tube goes into the intake, I replaced the lift pump with an aftermarket one and changed the oil and filter twice, now the level in the crankcase is slowly rising even appears to do it while sitting
Specifically, what kind of "lift pump" are we talking about?
- Mechanical (mounted to side of engine)
- Electric (does NOT have a lever sticking inside engine)
I would STRONGLY suggest you get a 'repair kit' for that pump which includes a fresh/supple diaphragm.
There is no need to replace the pump. If you have the ORIGINAL Kubota pump, it may be best to rebuild that one. (Aftermarket pumps may not have proper 'spacing' and the lever-arm may tear the diaphragm if not spaced properly)
ANOTHER OPTION:
Some folks prefer to simply put a 'blocking plate' over the hole where the pump mounts and instead use an electric lift-pump instead. This totally eliminates the need to ever mess with mechanical lift-pump again.
Of course, this option means tapping into the electrical system so the pump runs when the the key is ON. Mounting of the electric pump and plumbing it in may take a minute.
I don’t think this lift pump is serviceable as the bowl is press fit to the mounting