JD 870 Yanmar 3TN84 diesel in oil

[a1953mdl]

Hate to start my membership with questions, but it is what brought me here.
I have a John Deere 870 that has a Yanmar 3 cyl 3TN84 (iirc).
It is getting diesel in the oil.
I have been told this is probably from the lift pump or the injection pump.
Any ideas on how to verify which it is or which is more likely?
I started pulling the injection pump off but didn't realize you had to pull the front cover to pull the gear off the front of the pump first.
I have the factory service manual for the 870 but it doesn't cover the injection pump.
Can y'all help me.
Lee

 

[careyo63]

I would one cyl at a time remove the injector and check it for a cone shaped spay and check the cyliinder for compression if it comes up 450-500 psi let it sit under pressure and see if it holds or it leaks down if it holds and the inj.spray looks good replace it back and move to the next cyl. that will pretty much rule out any problems. If none move to the pump it's prob. Has a leaking seal. letting fuel into the motor. you can check the pump first but I find it easier to check the spray and compression than having to remove and check the pump.

carey

 

[a1953mdl]

Thanks for the reply. The tractor runs good and has plenty of power for its size. Can I rule out the injectors?
If the inj pump is the problem, is it the lift pump on the injection pump or the injection pump itself?
Would it probably be a seal that is serviceable by me or is this a trip to the pump repair service?

 

[careyo63]

Fuel Inj. pump itself. It has the Fuel injecter lines going to it.

 

[a1953mdl]

Okay, Thanks.

Since my tractor starts and runs fine, and is only getting diesel in the oil (and seems like quite a bit of oil). Is it possible that the seal that's bad is something I can replace (easy to get to) or is this definitely something I should just pay to have repaired? (work is slow, money tight)

I haven't seen an exploded view of an yanmar injection pump, so not sure where in one the leak would be coming from. I know on gas rigs if the diaphragm in the fuel pump has a leak you can get gas in your oil. But I realize a fuel pump and a inj pump are different designs. Sure wish my JD service manual would have at least covered the basics of the injection pump.

My question is because the tractor runs so good it seems like if the high pressure of the pump was leaking it would affect its running or starting. (I'm just thinking here)

If I have good spray pattern at the injectors, I can still have a leaking seal in the pump, right????

Seems like (iirc) that inj pump repair is fairly pricey, just trying to spend money wisely.

Please bear with me.

Lee

 

[NTEXSAM]

THE INJ PUMP IS LEAKING INTO THE CRANK CASE ..THATS THE ONLY SOURCE FOR DIESEL IN A CRANKCASE.. DO NOT RUN YOUR TRACTOR WITH THE DIESEL IN YOUR OIL....THERE USUALLY ARE O RINGS AN SEALS IN THE INJ PUMP ,NOT DIAPHRAM'S
THE INJ PUMP ISNT GEAR DRIVEN ,I DONT THINK. I BELIEVE THATS THE HYD PUMP WITH A GEAR.
THE INJ PUMP IS CONNECTED WITH A ROD TO YOUR GOVENOR SYSTEM.