Hi there and welcome to the fun that is my car.
The car in question is a 1980 Lancia Beta 1300 with 36,000 miles on the clock and was left standing for some years before.
I have just replaced the ignition coil, engine oil and filters and everything was going silky smooth I gave the car a drive till it was warm when I got home I left it until cold now when I tried starting it, it is VERY rough, not firing on all cylinders, and quite hard to start also sounds like there is sucking sound and then as soon as you let go of the accelerator it sputters and quits out, I tried it once more; same problem. Then out of intrigue I checked the oil which was abnormally warm and very thin I then smelt it and quite a smell of fuel. The smell of fuel in oil could be that unburnt fuel from the cylinder that wasn't firing going down into the sump. Not sure, my head isn't in gear.

How come in the space of hours there is a sucking sound (crack in vacuum pipes?) and the car is not firing on all cylinders as it sounds like a Canal boat then the fresh oil smelling like petrol. It's all making my head hurt!

Need to change that oil and filter again
