3406B getting fuel in the oil

Check injector o'rings.

 

what did they do the pump? The cam/lower half of the fuel pump is oil lubed and the upper half where the pumps are fuel lubed. If the oring in one of individual pump is damaged you could get fuel there. The fuel lift pump and the injector pass thru adapters leaking could also cause it. Any fuel line from the pass thru to the nozzle that is loose would cause fuel in the oil also.

 

3406Bs don't have injector o-rings, they actually don't even have injectors, they have nozzles.

Sounds to me like either a line to the nozzles has come loose or the bleed screw has started leaking on the side of one of the nozzles. I very much doubt the issue is in the injection pump.

 

I'll agree with Smokin Cat, odds are if you're seeing dye around the base of the valve springs, it's a nozzle problem or inner line problem. Nozzles will leak at bleed screw or further down where they're put together. If line is loose on internal side of pass thru adapter it should show up at the weep hole on the outside of the head. If it's between there and where it goes into the nozzle, it will show up inside, of course. If it has jakes, also inspect where the line passes under the jake assy. Seen a few over the years that were not centered and had clearance chafing. Another issue for your inj pump, you're saying replaced bonnets. The piece that threads into the inj pump is called a bushing. Underneath the bushing is an o-ring for upper seal. Any problem with that o-ring will put fuel out externally. The bonnet is the piece that is on top of the plunger and barrel assy. It contains a check valve and spring. At the base of the plunger and barrel assy. sits a timing spacer/slash lower seal ring. If you took the bushings out, odds are that debris fell down beside p&b assy to timing spacer. No grit of any type is allowable as this a steel to steel area and one spec of trash will put fuel into oil. At that lower ts/seal, you have fuel on one side and oil on the other. You will need to pull all p&b assy's, spacers etc and do a thorough cleaning as well as pump p&b bores . If you're not familiar with R&R of p&b assy's, don't attempt job. Rack has to be centered and several other things have to be exactly correct or you may have a run away on start up. As far as transfer pump, you would have to have a severely worn piston and bore problem for fuel to get into oil that way. That much wear would cause fuel pressure to inj pump problems long before fuel would get to oil. Not saying it can't happen, just never see it that common. Fuel starvation should show up well in advance of that situation. Good luck.

 

Sounds like one of the spacers that seals the bottom of the PBA is not clean or not flat. I always lap them with 600 grit on a flat granite block. They tend to get a ring made in them from the PBA being torqued down. You can always plug the fuel lines going into the pump and do a pressure test with 75psi of air.

 

Had an 87 Freightliner doing the same exact thing as what you describe. If you dont see any dye around the internal fuel lines, most likely you have a nozzle problem. I installed 6 reman nozzles and the problem went away. They are cheap enough to just change out all 6. Good luck.

-Mike