1 cylinder flooding, other 3 are fine??

[meinja]

Hi all,
Here's my situation:
1984 Mazda 626, 2.0 liter gasoline, 4 cylinder engine.
Quit firing on one of the cylinders the other day. Getting spark and gas to the cylinder, and timing is correct. Valves are not sticking and compression is good. The non-firing cylinder is actually getting way too much gas for some reason. I took out all the plugs and let it sit all day. I then turned over the engine without the plugs in it to help it air out some more. I noticed that on every stroke, a large vapour of gas would shoot only from the non-firing cylinder and not the others. The crankcase oil is saturated with gas also, I'm assuming because of whatever is going on with this cylinder. Any ideas on what is causing this? It is a carburator intake, not fuel injection. Also, I installed brand new mechanical fuel pump just in case that was why crankcase oil got saturated, but made no difference. Thanks!
Sincerely,
Jeff

[larsen_huw]

Dunno what carb you're using - but had a similar thing happen to me on my old Capri. The accelerator pump diaphragm on the carb had split, leading to neat fuel trickling down the inlet manifold and into the number 3 cylinder. Is it 1 of the middle cylinders which is flooding?

I know you say you're getting good spark to the flooding cylinder - but it may be worth rotating the spark plugs & HT leads just to confirm it.

The worrying thing is the petrol in the oil ... there's no way that should be there. If you've got good compression then it shouldn't be seeping past the piston rings. And theres no other way for petrol to end up in the oil - that I can think of - without having a hole in the cylinder wall. Which would obviously give you zero compression!

Take the carb off the manifold and see if there's any obvious signs of petrol leakage ... that'd be where I'd go next with the problem - although to be honest it's left me pretty stumped.

Looking at your spelling I'm guessing there's about 3000 miles of sea between us - which is a shame, as if you were local I'd come and have a look - always got time for old cars.