I've got a buddy with a 750 and all factory service manuals. I'll take a look at his tractor/paperwork tomorrow...I think in the x50 series tractors the injection pump is gravity fed. As an aside, I'm close to the purchase of an '85 650, which has the only two cylinder of the 50-series cut's. It's pretty thumpity, but runs sweet and is just the right size for my property and budget

 

It seems pretty clear your oil is getting contaminated with fuel. Start by fixing the primary or low pressure fuel pump. Next, change the oil and see how it runs. Should be all better. If it really is worn out, and I doubt it, and you can't stand the high amount of blowby, then route the blowby tube to the intake, downstream of the air filter. This will save the grass till you can rebuild the engine. And reduce smoke.

Wetspirit

 

Boss' grandpa has a 950. IIRC, there isn't a lift pump. Just gravity fed. Been a while since I've worked on it, though. Could be a seal out on the fuel injection pump.

One thing you could do after the oil change, (if it has one can't remember) is to close the valve on the bottom of the fuel tank, and see if it still makes oil, just sitting.

Before you mentioned the thin oil, I was thinking that you may need new valve guides. Oil could get passed that way as well. Although, if the compression is low, the fuel could be washing down the cylinder walls, too.

 

Thanks guys, I appreciate the info.

After reviewing the events, it makes since that it was/is indeed, fuel in the oil.
As I mentioned earlier, the oil was brown/black.
That is, when I pulled the dipstick just after it puked all over the grass, the brown was on top of the black.
It now makes since that the brown could've been diesel fuel and the black, oil.
However, the only thing that gets me on this scenerio is the lack of smell. It didnt then, nor does it now have a strong smell of diesel in the oil.
But all things considering, that is the only logical deduction.

There is no visiable lift pump on the outside of the engine. The fuel comes down from the tank, through a filter and right into the banjo bolt on top of the injection pump.

Could the pump have an internal leak allowing fule/oil to mix?

Through this all, the engine has ran fine and has had no change in either performance nor the amount or color of exhaust.

Thanks again guys, I do appreciate the input.

Rich.

 

That seems like the logical conclusion. Probably the seal on the pump driveshaft has failed.

 

I changed the oil this afternoon and it poured out like water. Also, I could smell the diesel in the oil as it drained.

With fresh oil, I fired it up and mowed the backyard. This time, there is a lot less blow by than previously mentioned and no hint of liquid coming out of the blow by tube.

Im guessing that if it were a bad seal, the problem would still exist. However, it would seem that (right now) the problem is not present.
That would lead me to believe that it may have been an stuck injector after all.

???
Rich

 

I'm thinking you didn't drive the tractor long enough for the leak to overfill the crankcase enough so that it starts blowing out.

 

I wouldn't recommend that at ALL!
If his engine has a habit of puking fuel contaminated oil out the breather, taking it into the intake would be a bad move indeed!
I had a 1981 Toyota diesel with that kind of blowby vent connection from the factory. After the engine got old and developed more blowby, on long highspeed interstate runs it would pool oil up in the valvecover and then it would puke healthy slugs of hot Delo-400 directly into the intake!!! It was a dang good thing the clutch was fully engaged, or I would've had pieces of diesel engine all over the road! An AMAZING smoke show nonetheless!!! LIke kicking in the afterburner for about 10seconds!
I fixed this VERY unsettling quirk by REMOVING the factory valvecover breather hose where it connected to the intake manifold.. I routed it into a breather bottle (a-la Dodge CTD) and I had no more runaways... I would dump the oil that would occasionally accumulate after a long hard trip.


K.

 

If you think the injector was the cause then get an oil analysis done to see if it has fixed itself.

 

Pretty good chance that it did not fix itself.
I changed the oil Tuesday and mowed the back yard. While mowing, there was significantly less blow by, far less than even the first time I used it after purchase.
I checked the oil last night and again, it just drips off the dipstick like water and this time, a very strong smell of diesel fuel.

Im going to start with the injectors first.
I will pull the injectors out and have them tested.
If those are ok, I will then pull the injection pump off and send it in.

Anyone know the "tips-n-tricks" or things to be watching for while pulling/replacing the injection pump on a Yanmar like this?

Rich

 

I would put the engine at TDC for #1 cylinder before removing the pump. Mark everything. On re-install, there is a timing proceedure in the manual.

 

Thanks.

The last time I used the tractor, the fuel tank was sitting just at the 1/2 mark.
Last night I pulled it around by the garage and noticed that the fuel tank was just under 1/4.
I can also see the fuel sitting on top of the oil by pulling out the dipstick.

So, I question you guys:
As it would appear, fuel is draining from the tank into the crankcase as it sits.
Would that deduce injector or injection pump leak?

Besides setting TDC on #1,
What is the process to pull this injection pump if thats what I must do?

Rich.

 

You can find out if it's an injector by pulling them one at a time and looking for fuel sitting on top of the cylinder. Do this after the tractor sits for a day or two.

 

That is the current plan actually.
Were suppose to get a break in the heat this weekend. Im hoping it'll be cool enough not to melt me as I wrench on it this weekend.

Rich.

 

It can't be an injector leaking into the cylinder or you would have had a hydraulic lock. And I don't see how the fuel could have filled a cylinder, passed through an open valve and found its way to the crankcase. The only practical way would be down the cylinder wall past the piston and that would be fairly slow, and you would have had a hydraulic lock unless you were incredibly lucky and it all went out the exhaust on the exhaust stroke. The fuel must be leaking from the injection pump seal where it is driven from the engine. Look there first.

I'm glad you found out it's fuel contamination and not a worn out engine.

Wetspirit