Fuel in my oil

loggerman1959 · June 06, 2018, 10:58:47 AM

I have a JD 450 dozer I use for landing clean ups and such . Its a late 70s model , but I've noticed fuel mixed in with my engine oil . I thought it was a leaky fuel pump , so I changed it , and the oil , but I'm still getting fuel in it . Does anyone know what could be causing this , or have a similar problem with theirs ????

mike_belben · June 06, 2018, 11:15:31 AM

You changed a transfer/lift pump or a high pressure injection pump?

Its common on inline plunger and barrel style injection pumps for a bad O ring to leak fuel from the low pressure galley down into the cam area which drains lube oil back to the timing case and into oil pan. This will usually start showing up as a bit of a rumpity rough start after periods of sitting, like air after a filter change or whatever. The low pressure galley leaks down so it basically loses prime every day.

loggerman1959 · June 06, 2018, 12:36:56 PM

It starts and runs good , obviously I'm not running it because the thin oil .

rjwoelk · June 06, 2018, 01:43:42 PM

The hand primer pump on my 3020 caused me issues once. Then the Injector pump caused the same problem 2 years ago.
We had a old 730 jd that did it from the fuel pump, blew the seal and pumped into the crankcase. Did it twice in a summer.
The other thing may be if you have a cracked internal fuel line.

CX3 · June 06, 2018, 01:53:30 PM

It has to be in the injection pump or injectors. There is no other way fuel could get in the oil.

Are you sure it's fuel and not antifreeze ?

CX3 · June 06, 2018, 01:55:31 PM

I'm gonna say it's not injectors because I can't think of how that would get fuel in the oil unless your piston rings are so worn that fuel is seeping in past them. But that sucker would be hard to start in July in that case.

Skeans1 · June 06, 2018, 02:35:42 PM

My money would be nozzles, You can have a good compression engine but still have oil and fuel go past the rings.

Stuart Caruk · June 06, 2018, 03:05:20 PM

My International 500C had a leak in the seal of the fuel injection pump, which caused diesel to leak into the engine, filling up the crankcase. I had to pull the pump and rebuild it. Problem solved.

loggerman1959 · June 06, 2018, 04:09:56 PM

I thought it might be the lift pump , so I changed that , the injector pump was rebuilt a few years back .

Mapleman · June 06, 2018, 06:39:20 PM

If the injector pump on your 450 is set up like the 350, and I think it is, its driven by a shaft attached to a gear in the timing gear train. There are two cup seals on that shaft, one to keep the engine oil in the engine and the other to keep diesel fuel in the injector pump. That seal might be bad. The injector pump slides over that shaft and its possible to invert the lip on the seal for the diesel side when installing the pump because of the way it faces. There might be some special lube specified by JD for those seals too, but I can't remember for sure. When I did mine some years ago, I took the injector lines off the injectors, bent them back slightly so they'd clear, unbolted the pump and slid it back off the shaft.

Hope this helps, and good luck!

mike_belben · June 06, 2018, 11:31:59 PM

Good info. Thanks for sharing.

carhartted · June 07, 2018, 01:17:51 AM

You may have a stuck injector which is not building up enough pressure to spray properly. The fuel will just sit on top of the Piston and eventually go past the rings. To check crack each injector line one at a time at the injector while running. The engine should start to miss, if it doesn't then that's the hole with the issue.

loggerman1959 · June 08, 2018, 08:31:52 AM

Thanks for all the responses folks , ill get er figured out

loggerman1959 · June 08, 2018, 12:18:25 PM

It seems to be filling with fuel as it sits . Is it possible that fuel cam gravity feed through the lift pump and into the crank case while its sitting ?

bushmechanic · June 08, 2018, 07:24:50 PM

I'm guessing that that machine has the fuel tank behind the seat so if the fuel level is higher than the engine then yes it can syphon down into your engine. There are only so many ways fuel can into the crankcase. If you changed the lift pump then that should be eliminated. If the shaft seal on the injection pump leaks it can enter there and other than that if you have a bad injector tip it can leak in there.

loggerman1959 · June 08, 2018, 08:44:18 PM

Bushmechanic , while it sits , or running ?

Dave Shepard · June 09, 2018, 01:30:48 PM

On fuel systems that have a return line to the tank, a bad return line check valve, or a plug of some kind, can blow the seal out of the injector pump.