# Loose gas cap cause problems?



## Star1pup (Aug 3, 2004)

I had my 9.9 Evinrude 4-stroke lose power a couple of times. It only lasted about 30 seconds, but it also seemed to hesitate when I advanced throttle. I decided to take the tank home and use the fuel in my tractor and then add fresh gas. When I pulled the tank I found that the gas cap was very loose. Would this cause the problem?


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## GPtimes2 (May 14, 2006)

No, you need the tank to be vented. Actualy, you want to check the vent screw on top of the cap and make sure it is loose. A sealed tank could cause you to loose gas feed. Even with a loose cap it could pull down and cause a vacumn while you are useing it. You could also have had air in the primer bulb that could have migrated into the carborator.


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## DaleM (Apr 5, 2004)

Some new motors must have the caps on tight then loosen the vent, if it has one. I know the 9.9. merc 4 stroke we have in Canada you have to have the cap tight or the same thing happens. I'd try it again with the cap on tight.


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## Fishin'Fool (May 4, 2006)

Sounds like bad fuel. Small amount of water in the fuel will act like that.
As far as the gas cap being too loose, the engine doesn't even know
there _is_ a gas cap. Unless of course there is some new style cap
that only vents properly when tightened down...........? Not.


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## Star1pup (Aug 3, 2004)

My first thought was bad fuel, which was why I was bringing it home for the tractor. I don't have to paddle the tractor if it quits.  

As for the cap there is no vent like in the older or 2-cycle motors I've owned so I think the loose cap might at least have added to the problem. Just not sure. It was tight all last year and it ran smoothly.

Anyhow, I'll use new fuel and put the cap on tight and let you all know what happens. An outboard mechanic also told me earlier that it is a good idea to run Sta-Bil in the 4-cycle outboards.


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