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2003 Mercury 3.3 outboard - Fuel cap leaks??

J

jonelli

New member
I can't figure out how this thing is leaking, but when I lay it on it's side, it leaks gas out of the filler cap that SHOULD be sealed up when you tighten the cap real good. I already bought a new gasket for inside the cap and it didn't make ANY difference.
Before I go spend another $40 on a new cap which I'm not convinced is the issue, does anybody have any knowledge about this problem?
It makes it impossible to transport in the back of my car.
 
Don't you have 2 gaskets, one for the cap proper and a second for the vent? A simple lay it down like you do in the trunk of your car and watch to see which one is leaking.
 
Texasmark said:
Don't you have 2 gaskets, one for the cap proper and a second for the vent? A simple lay it down like you do in the trunk of your car and watch to see which one is leaking.
Click to expand...

It seems to be an all-in-one. Here's a pic of before I swapped the rubber gasket inside the gas cap, but it didn't matter, same issue.MercGasCap.jpg
 
It's leaking from under the cap, where the tank filler neck is. As if it isn't tight down over the neck to seal it. But it's as tight as it will go. I don't get it.
 
Solved the mystery.
I even made a thick round rubber gasket to add to the cap and it didn't work.
Then I put my glasses on and carefully looked further and found this. Yes, that's a crack and it is where it leaks and explains everything.

I may drain the fuel, let it dry out and then try to fix that. FuelNeckCrack.jpg
 
"Then I put my glasses on and carefully looked further and found this."

You know, these things do happen to others too. Grin. i have magnifying glasses of some sort every place I have to see something up close. Amazing what one sees when they get focused and a large enough picture to be recognizable. Glad you found it.
 
Don't try to fix it.....you should replace the fuel tank.
If there is a gas leak in the back of your car, there could be an explosion when you open the back.
Better to put in a new tank.
 
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