D4600 Fuel in oil

I am in the process of swapping an engine in a 9U D6 as a result of the operator NOT stopping when fuel was getting in the oil. In the end it might result in scrapping the machine because the replacement engine has shown no signs of running......YET! Still want to try a set of injectors in it before I give up on it. Also need to set the governor on the pony motor and fix the pinion latches because as soon as it hits on a cylinder, the pinion pops out. I think the operator has been holding up on the pinion shift lever to keep it in until the engine takes off. Since I don't have the clutch installed yet, (no pinion shift mechanism) i cannot hold it in, so it needs fixing properly.

Thank you all for the direction I need to go. I have seen a drip under the filter housing coming from one of the copper drain lines, It's a slow drip, but I haven't figured out where the line runs to. I do have a parts book and will start looking into the seals you talk about, and it's time to locate the drip also. My dad,gone now, bought it with a stuck motor in 1995, and had been setting for at least 15 years. I got it unstuck and put new sleeves and rings in it. Some one before me bored the block out to receive 9U sleeves. Under the injectors was a wafer shaped piece that had a small hole, I think around .014. After cleaning them out all the injectors worked properly. I had to change the clutch also, it had a bushing shot and vibrated real bad. I put a later clutch in it that had a bearing to keep it centered. I have recently put a 5hp briggs motor on it to start the pony motor. I can start it really fast now. I've done all the work on it, but understand things better when I take things apart rather than reading it in a book.

Its been a LONG time since I worked on a 4600, the copper lines, one line is an injector leakage line and will usually drip slowly when the engine is running. The other line should be picking up Injector Pump leakage which goes back to OM's comment about changing the 2 seals on the Gallery. If there is a 3rd line(depending on vintage) it is a drain off for the fuel filter tower. Later Series should have 2 of these lines tied together. Like I said, its been a LONG time since I worked on one of those but that's the way I remember!

No misfiring? Any "fuel" smoke? I am wondering if the injectors might not be performing up to snuff and unburned fuel is working past the rings, but that usually results in a case of slobbering if its very bad and slowly "making" oil.

The fuel gallery seal next to the filter housing will leak directly into the crankcase. Any leakage is trapped in the gasketed joint where the pump housing mates to the filter housing and will find its way through the drive and bearing at the bottom. If the one on the rear of the pump housing leaks it should fill the governor/injection pump oil reservoir to overflowing and may find its way through the seal on the front of the pump camshaft and into the crankcase that way.

So do not expect a telltale line to let you know a fuel gallery seal is leaking. The only way a telltale should drip from one of these seals being bad is if the rear one filled the injection pump housing so full that fuel worked up around the lifters and collected in the drip tray like pump leakage and came out that telltale. I expect you would also see leakage at some gaskets and the governor control shaft seal etc as well as finding the sump overfull of fuel instead of level full of oil.

I guess you might consider a drip from either the injector return or the pump housing as fairly normal on an old engine.

Take the two bolt (square) cover off the side of the filter housing and you can look in there and see if fuel is leaking from the joint.

The fuel transfer pump has dual shaft seals and has a vent line ported between these seals. This line is on the right (operator side) of the fuel transfer pump, fitting located behind the fuel filter tower drain tube, extends towards the operator then down towards the belly pan. The fitting found on the left (radiator side) of the fuel transfer pump goes behind the injection pump and "T's" into the 1/4" line connected to the top of each injector which vents the injector return directly into the fuel transfer pump.

Ignore the new pump on the right. The left should match yours

[attachment=41851]IMG_7351.jpg[/attachment] shows rad side port with installed fitting

[attachment=41852]IMG_7352.jpg[/attachment] shows operators side (vent) port without fitting installed

If diesel is getting past the shaft seal, it should be vented towards the belly pan/ground at a steady drip rate. If the oil seal is leaking, you will have the black oil collect at the end of the vent tube and not drip rapidly due to not being pressurized. Cap the end of the vent tube with your finger and observe the colour of the fluid. If this vent tube is plugged and both seals are leaking, there is a chance of diesel to get into the engine case/oil.

To access the transfer pump vent line fitting, you will have to close the fuel tank fuel supply valve, drain the fuel filter tower and now remove the fuel filter tower drain tube (2 bolts). The fitting is now accessible. If you have gone this far, might as well remove the compression fitting nut, slide the tube out of the actual fitting and blow it out from the transfer pump side towards the other end.

If the above isn't the case, stick with the gaskets as mentioned in the replies which would be the best cause for fuel in the engine case/oil