<VV> HELP! Gas in oil pan (or petrol in sump, as we would say!) NO CORVAIR but I am desperate!

[Alan and Clare Wesson]

Hi all

This is not a Corvair question, but I am getting quite desperate! Can anyone 
help me? The oil pan (sump) of my Lancia Appia S3 (that's the white one that 
I came to Germany in, Thomas!) gets full of gasoline (petrol) over about a 3 
week period of normal driving - last time I drained it there was about a 
quart too much liquid in the oil pan, and what was in there was a mixture of 
oil and gas. And now it is happening again. I am worried about destroying 
the engine!

So... as the mechanic who works for me and I see it, there are three 
possible causes:

a) carburettor needle valve (we've checked that - it isn't that, and anyway, 
carb is new)

b) fuel getting past the pistons and into the pan, if one or more cylinders 
have broken rings - we have checked the compressions and they are all 
normal, and there is no blow-by (always a problem on these engines if a ring 
goes - they begin to smoke a lot into the engine compartment, and this one 
isn't doing). We haven't done a leakdown text yet, but we will soon. I don't 
think this is the problem, though, although it does have a very slight 
misfire, that clears itself over about 2000 revs.

c) fuel pump diaphragm failed and leaking fuel into engine a la Corvair - 
it's not that because there is no path for the fuel to follow through into 
the pan with the pump on this engine.

So... we have investigated all three possible causes that we know of, and it 
doesn't appear to be any of them! Does anyone know of a fourth, before I 
ruin my engine? I am now taking the car off the road until I fix the 
problem, because it will undoubtedly trash the engine if I carry on driving 
it with thin oil mixed with gasoline!

Cheers

Alan