50 Mercury gas tank vent

[Rand]

How does it work? How do I clean it
When I fill it up it gurgles and bobbles out the top when its getting full. And with a full tank it makes the garage smell of gas. When down below full everything is fine
Thanks for your replys
Be safe out there!

[19Fordy]

As I understand it the little tube on the inside of the filler pipe goes into the tank and allows the air to escape from the pressure created when tank is being filled. With today's rapid filling pumps, the vent tube is too small to evacuate the pressure build up rapidly enough to keep up with the in coming pumped gas. Got to fill slowly. Same is true on my 40 Ford. Take a metal coat hangar and run in down the inside of the vent tube to see if it's clear. I suspect that if that vent tube was larger dia, all would be fine.

[19Fordy]

Here's some great info from another thread about this same problem.
https://www.fordbarn.com/forum/showt...+fill+gas+tank

[Rand]

Thats a lot of great info 19Fordy Thanks!
Ill look it over tonight when I sit down and have a free moment. Thanks again!

[Black Fifty]

Originally Posted by 19Fordy

Here's some great info from another thread about this same problem.
https://www.fordbarn.com/forum/showt...+fill+gas+tank

19Fordy, after reading that thread link, you were going to let people know if that vent mod worked. Did it end up helping you? Was also wondering about how to keep metal shavings out of the tank, unless you pull the tank before drilling. Or were you talking about the filler tube vent mod?


Mike

[51 MERC-CT]

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Originally Posted by Rand

How does it work? How do I clean it
When I fill it up it gurgles and bobbles out the top when its getting full. And with a full tank it makes the garage smell of gas. When down below full everything is fine
Thanks for your replys
Be safe out there!

It is virtually impossible to clean the vent tube as the hole in the top of the tube is hidden behind a flap that is welded to the filler tube.
The possible reasons for gas smell when full are a defective filler cap vent or a gas leak at the flange where the gas gauge sending unit bolts to the tank.
Solution otherwise is to not over fill and slow fill.

[19Fordy]

Originally Posted by Black Fifty

19Fordy, after reading that thread link, you were going to let people know if that vent mod worked. Did it end up helping you? Was also wondering about how to keep metal shavings out of the tank, unless you pull the tank before drilling. Or were you talking about the filler tube vent mod?


Mike

Yes, I did do the vent modification and it helped. My tank is plastic. I drilled the top of the tank in the car near the gas tank sending unit. I kept the shavings out of the tank by attaching a little can to a bendable metal rod and inserting thru the opening for the gas tank sending unit to catch chips. If the tank were metal, I would magnatize the drill bit and then put grease on the tip to help catch chips. If you have a fuel filter near the tank it will catch the chips. Plus, you can use an extendable magnet or a magnet on a stick to pick up chips if you insert it thru the gas tank sending unit opening. The gas pumps today pump the gas at a much faster rate than in the 30's thru the 50's so it will never be perfect. Here's a photo of the filter that filters the gas near the tank exit. Also, a photo of the fitting on the top of the tank near the opening for the gas tank sending unit.There's another filter near the carb.

[19Fordy]

Thanks 51: I didn't realize that.