Not to start an argument.....

[PTmowerMech]

Maybe it would make more sense if you think about the spark as a heat source. The gas is ignited by that heat source. Water is a coolant. So the water cools the spark aka heat source below the temperature required to ignite the gas. Therefore the gas doesn't ignite therefore no run. Also if the spark plug gets wet with water and water is conductive of electricity it grounds out the spark.

A combustion chamber is cold when an engine is trying to start.

About the water, keep in mind, I'm only talking about a small amount of water in the float bowl. Due to sitting and collecting moisture from condensation.

That would get sucked up into the intake fairly quickly. Especially if the carb is choked. Then once the gas starts getting sucked up, it would/should ignite. That would evaporate the water and send it out the exhaust.
It is a cup or more of water, I could see why it wouldn't start. But I'm only talking about maybe two table spoons.

 

[Hammermechanicman]

A small amount of water in the float bowl can cause a no start condition.

 

[PTmowerMech]

A small amount of water in the float bowl can cause a no start condition.

I realize that. What gets me is why the suction from the pistons doesn't force the water up through the carb.

 

[slomo]

H2O is heavier than gas???

 

[Hammermechanicman]

Just finished my third push mower of the last few days for water in the gas. Every one of them said the mower quit working after they filled it up. One guy says he uses one of the new politically correct gas cans. I guess they aren't as air tight as the government thought. E10 makes me money.

 

[PTmowerMech]

H2O is heavier than gas???

Right.

That's the only thing that makes sense. That it's too heavy for the suction from the piston, and the push of the fuel pump, to push gas up through he main jet.

 

[mcspeed]

IMO the water is not as deleterious to combustion as some may think. Yes it wreaks havoc on parts corrosion though. One thing my old school dad would do to help remove carbon from the engine on a car is pour water into the carb while running. I did it myself many times. Sure it would cough a bit but it ran and had combustion.

 

[davis2]

Not sure but this might be a fuel problemView attachment 69307

Definite maybe!

 

[Gym123]

Cannot see the water. Can you add food dye to water to make test more interesting?

The bottle on the left has a milky appearance at the bottom, maybe 1/8"-1/4" high, the one on the right doesn't.

 

[Gym123]

I don't know what/if anything was added, but this came out of the Ariens 42" I got recently. It started extremely easily, but as the previous owner wrote in the ad, 'white smoke' began not long after the engine warmed. The first thing I gig after looking into the tank was drain it, then refill. I didn't bother with the filter at that point and the white cloud stopped. The blue cloud, OTOH, was obvious. The cloudy gas is the way it looked immediately after filling the bottle and the other photo shows how it settled out after a couple of hours. There's no phase separation and in this area, we can't buy Ethanol-free.

The third photo is from a boat I worked on- the fuel tank had filled with water and this was the result of people trying to start the engine- it had Volvo-Penta fuel stabilizer, added during Winterization. Obviously, this is an extreme case, but it shows phase separation.