Vapor Fuel Question

[vascon2196]

Folks...I'm having problems with my vapor fuel system on my Quadricycle engine and was hoping for some guidance.

My engine runs fantastic off a fresh pour of Coleman fuel. After a minute or so it stops working. If I take out the "old" gas and introduce new fresh gas the engine runs great again. It seems like it runs off the vapor only if it is freshly poured? Does this make sense to anyone?

I have a vertical gas tank...should my fuel level be higher and closer to the intake tube? I squirted some starter fluid into the intake and the engine ran so fast it almost jumped off my worktable.

I have been looking through many threads here on the forum but I feel this problem I am having is somewhat unique.

 

[Jasonb]

Wonder if the vertical tank has a smaller surface area than a horizontal one so you are getting less vapour produced?

 

[canadianhorsepower]

Wonder if the vertical tank has a smaller surface area than a horizontal one so you are getting less vapour produced?

I think thats whats wrong also:hDe: by having an horizontal with the engine vibration it will generate for fume. I'd like to see refilling the reservoir with the same coleman fuel what would happen, If it would start again

 

[Blogwitch]

Your problem is almost definitely caused by your upright tank, it just doesn't have enough surface area to supply the engine contiuously with vapour.

That is how a vapour carb works, the air is drawn in and as it crosses the surface of the fuel, it makes the fuel evaporate from the surface. If your surface area is too small, once the engine has drawn the vapour off the top, there is not enough vapour left to continue with combustion, so the engine stops. When you change the fuel, that action will refill the area above the surface of the liquid with fresh vapour and the engine will run again until there is no vapour left.

By putting the tank on it's side, depending how long it is (at least 2 times the diameter), and how far up you fill it (50% full should do it), then the surface area should be larger and should be able to supply more vapour than the engine can consume, so it should run continuously.

I hope this helps a little

John

 

[AussieJimG]

Everybody has problems with these carbys but I agree that the first thing to do is to increase the surface area. Then the fun begins.

They seem to be very susceptible to filling level. This makes sense in a round tank since the surface area changes. But it also happens with a square section tank. Dunno why.

And then they will run for 30 seconds and then stop. But if you come back later, they will run for another 30 seconds and then stop. Possibly due to evaporation cooling the liquid so evaporation slows thus limiting the vapour. But we tried warming the tank without success.

And bubbling the air through the liquid doesn't make any difference either.

So good luck and lots of us will be watching.

Jim

 

[vascon2196]

EVERYONE!

Thank you so much for the information!

I came home, filled the tank 3/4 full, and spun the flywheel.

The engine started right up and kept running strong as hell.

I stopped it intentionally and started it up again and it ran great again! It also slowed down and sped up based on the air intake screw.

I will switch over to a flat horizontal tank next. For now, I'm going to run it some more until I'm ready.

Thanks again,