diesel in my oil

[captainsteve]

I have changed the lift pump on my Perkins 4-108. I still find diesel in my oil. It seems that the diesel fuel does not enter the pan until after the engine has run and been shut down. After changing oil and filter upon installing the lift pump, I ran the engine approx 3 hours. Minutes after the shut down I checked and found no evidence of diesel in the oil and the level was the same as when I changed it. Six hours later I found at least a quart of diesel had seeped in. Would the seal in the injection pump leak only when not operating and not when it is? Are there other ways for fuel to enter the oil system? The engine performs well by the way. PLEASE HELP!
Steve

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[brianhumber]

I am assuming its a mech lift pump, and I have had lift pumps leak into sumps before. Did you overhaul or is it a new one?
Injection pumps can leak past at the drive shaft seal but a quart is lot.
Is the feeder tank higher than the lift pump, can you unbolt the lift pump whist still keeping the pump fuel lines connected. You would then be able to see if fuel is coming out of the pump whilst stopped due to the head of fuel in the tank.

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[captainsteve]

The lift pump is new. The pump is higher. Could the injection pump leak only when the engine has run, been shut down, then let set? No leaking evident while engine is running?
Steve

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[Born_Free]

There are only two points at which this can happen, The lift-pump and the injector pump. Must agree with the others, a quart is a lot. Suggest that in turn you release both pumps after running and see if either leaks. Just occured to me there could be a third, worth checking the injectors to see if they are Ok. it may be possible that one of them is leaking the low pressure spill return fuel back in through one of the combustion chambers, so also check that there are no restrictions on the return pipe. The problem could also be being made worse if there is a blockage on the crankcase breather which may be causing a pressure drop in the sump as the engine cools thus increasing the flow of the leak.
A real puzzler this one as it's hard to envisage how that much fuel is getting into the oil, especially when you say the tank is below the level of the lift pump, mind you if its above the level of oil in the sump and there's a leak somewhere to the sump then the fuel will try to find its own level between the two. I always close my tank fuel feed tap after shutting down the engine, and suggest you do the same if you've got one, and if you havn't then you really should fit one. This will at least prevent fuel flowing in from the tank, although it can't be considered as a fix for the problem.
Wish you all the best with this one, hope the above helps.

<hr width=100% size=1>I have nothing to declare, except my genius
(Sorry Oscar)

 

[mtb]

I cant see it being the dpa injection pump !! as your aware it runs under tremendous pressure and would soon fill the sump !!. Cant see it being an injector either because you have stated, the engine runs well. Again injectors work under high pressure 150 atmos !!, even if you have a leaking injector which by the way is normally not a clean end to injection, common cause being worn broken / needle seating and or weak spring. You would notice this because of rough idle black smoke engine missing, it would be worth taking the em out and doing a visual inspection see if they are clean if you have access to equipment check their breaking pressures and so on.
You say you changed the lift pump which is the most likely fault but if you've changed it and still the same !!.

What gear box have you ? if yours is using atf you may have a leak, the bellhousing filling then once engine is off siphoning into sump through crank seal. I know it sounds daft but have to consider all options
Used to get this fault with listers and once the engine had enough diesel they could run till bang .

cheers
Mick

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[choulihan]

We have a 44 Brewer sail boat with a Perkins that is getting diesel in the oil. We just had the injector pump re-built at a cost of $400 and we are still getting diesel in the oil. We get 1-2 quarts after motoring for 3 hours. We are taking the pump back to the man who re-built it and he said he'd take another look at it. Is there any other way that diesel could be getting in the oil other than from the pump?

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[boatless]

Is the external plumbing all as built? Rocker cover breather? I was thinking the other way round... as the engine cools it would normally draw a a litre or so of air, so could it be inhaling diesel instead? Can't imagine why though, would expect air to leak in around oil filler, dipstick etc..

<hr width=100% size=1>my opinion is complete rubbish, probably.