Possible diesel in oil crankcase??

[jibronee]

I just did a zf5 swap and at same time replaced my 6.9 with a supposedly good used 6.9 that had been sitting for @ 5 years or so. Started right up and seems to run good. But I thought I had a valve cover oil leak that was dripping down on exhaust pipe, from exhaust manifold on driver side. Well there wasn't an oil leak. I thought it could have been a leaking/bad injector so I swapped out that injector and the leak seems to have stopped.

Is this a possible scenario to have a bad/leaking injector that weeps out?

I changed oil and I'm pretty sure it had diesel in it.

Appreciate any advice as I'm new to 6.9 diesels as this was an 86' project truck I bought almost 15 years ago and just now getting it going. Love the 5speed!!! Thanks!!

 

[gandalf]

Oil in the crankcase is an absolute problem. That's something you've got to look into (no pun intended).

The most likely culprit would be the lift pump, the fuel pump mounted on the passenger side of the engine, toward the front. That would be the stock lift pump. If the truck has been converted to an electric fuel pump you may disregard this.

The lift pump has a flexible rubber gasket between the pump chamber and the crankcase. If that gasket rips the pump will pump diesel fuel into the crankcase. That is something you want to avoid. It dilutes the oil so it doesn't lubricate as well.

You can either outright replace the lift pump (they're cheap enough), or watch the oil level very carefully. Personally, when the truck has been sitting so long, I'd simply replace the lift pump.

 

[Nero]

Oil in the crankcase is an absolute problem.

Yes mm bad oil in the crankcase

 

[Austin86250]

the only reason for desiel to be in engine is bad mech fuel pump or wash down
leaky idi injectors don't put oil in crankcase like an lb7 does because there injectors are under valve covers

 

[Nero]

Fuel in the crankcase would have to be a lift pump, or the shaft seal for the injection pump. But I've heard the injection pump front seal is dang near never the culprit.

There also isn't enough fuel in the injectors at key off to make a big difference in fuel dilution to the oil, normally that would just cause hard starts/long cranks.

 

[Black dawg]

Fuel from fuel leaks can get into the engine oil through the valley pan......CDR grommet, Have seen holes in valley pans before.

 

[jibronee]

I'll start with my lift pump. I put a brand new one on, but maybe it's defective? By removing the lift pump, will I be able to see a leak/residue? Or just hand pump it and look to see if it's leaking?

When I compression tested engine, all cylinders were in the mid 400 range so hopefully it's not wash down past rings.

 

[gandalf]

If it is the lift pump diaphragm you should be able to see a rip in the diaphragm. If that is okay fill your oil so it indicates exatly full, and then watch it carefully.