Diesel fuel leaking into engine oil

[Geoff H.]

I have a Ford Lehman 120 recently rebuilt in Panama (not recommended.) Checked oil yesterday (about 100 hrs since last change) and level on dipstick was high and definitely diluted with what I believe is diesel. I know I should know what causes this, but duh, what causes this? Now what?&*%$#@@

[a64pilot]

Most likely you have a mechanical fuel pump mounted on the engine. This pump is a diaphragm pump and the diaphragm has torn allowing diesel fuel to enter the crankcase.
This is not the only possibility but most likely. If you do not have an engine mounted mechanical lift pump next most likely suspect is the fuel injection pump itself having a seal leaking


Sent from my iPhone using Tapatalk

[Pete7]

Didn't Ford put the injectors in the rocker cover and a rubber seal were the injection pipes go through the cover? Certainly the Ford Dover and Dorset range were like this. If the Lehman is like this then a leak at the injector will fill the engine sump nicely.

Pete

[rw58ph]

I agree it probable the fuel pump. We had the same thing happen on the DD 671

[Geoff H.]

Thanks for all replies. We pulled the valve cover off and found a tell tale pink (fuel) at several of the injectors where they are threaded into the block. Perhaps the little copper washers used there had been re-used....?
But on disassembling the fuel pipe (which snakes through and connects to the injectors, it CAME APART into two pieces. Suspicion is that it had been torqued down without an even distribution of torque, i.e. that rather than the recommended 'little at a time' method of tightening the connections, some part got tightened down prematurely, and with subsequent vibration it came apart eventually.
Anyway, we've ordered a new one and should have tomorrow, and hopefully that and a couple of fresh oil flushes, will be that.