Gas leaking from gas cap

[89conbrio]

I recently bought a 1999 Santera. Over the weekend I was doing some work on it in the driveway and noticed gas oozing from the gas cap. I opened the cap and gas started overflowing over the side of the boat. A few minutes later there was no sign of gas in the fill tube????? Does anyone know what the cause of this would be? I can't seam to find a gas vent on the boat either? The tank reads full, but it was ran for about an hour when I bought it so there shouldn't be gas in the fill tube at all. It's like it got a suction some how.

Any advice I could get on this would be much appreciated!

Thanks!

[jet]

Do not fill to the top and then leave it out in the sun. the tank will expand and then spit it out of the vent usually or in your case the filler tube. Your vent tube might be clogged up? Spiders?? dirt dobbers?? It on the other side. You can try to blow in it or take it apart. Its about 15-30 min job.

[sydneyACE]

Fuel expands and contracts a LOT with temp variation. This is why you sometimes hear it's best to fill-up your tank in the early morning because the fuel is at it's highest density and you'll get more for your money. Personally, I think with the below-ground tanks that are used these days, the fuel temperature probably doesn't fluctuate very much.

Anyways...

Try and leave a little room in the tank for expansion when you fill-up, especially if you think the fuel is cold and are expecting a hot day.

Also def check to see if your vent is clogged or something. It prob should have been coming out of there first, although some fuel vents have a check valve in them that prevents this.

If your tank isn't venting enough you may have fuel starvation issues if you run it at high speed for a while because it will create a vacuum in the tank. My brother and I fixed an old Reinell at our shop once that had that problem.

Man I ramble on a lot.... Sorry

[jet]

sydney..ditto on the gas temp underground. The temp down there doesn't fluctuate very much.

[89conbrio]

Thanks guys. However, I did not fill the boat up... When I bought it it had a full tank. But also I test drove it for about an hour before towing it home. I would think this would have burned off at least a couple gallons. Certainly enough to clear the fill lines.

In doing a little more research (because I couldn't find the gas vent), I found out that it vents through the Perko gas cap. The vent tube is an inch down from the top of the fill tube. Could there be a problem with my Perko gas cap? I'm not 100% sure how it vents? Could it have been too tight? Or is there a way to test the vent tube to check for an obstruction? Could I blow air down it?

As for the temperature. I kept it in my garage the night before where it was probably 70 degrees, the following day when the gas started leaking it was 80 degrees. Not really a drastic change but 10 or more degrees.

[sydneyACE]

Hmm... That's a little interesting. It's hard to say exactly what caused your prob. It's a little odd because you ran it for about an hour which should have drained the fill tube.
Is your cap similar to this one here?
http://www.perko.com/catalog/category/fills_and_vents/product/454/

Were you maybe sitting at an angle?

10 degrees would prob be enough to cause some decent expansion. In order for your tank to vent fuel, the fuel level would have to be at least as high as the base of the filler neck (where it meets the tank). Otherwise it would just vent vapor (which is what it's supposed to do). If the filler has an integrated vent tube it shouldn't really matter if your vent tube is clogged, that would just make it bubble-up/overflow when your filling the tank.

It's hard to say without seeing your set-up, and it's hard to explain stuff like this without nifty pictures to help.

I would say this isn't a serious issue. It's not fun to spill gas all over the side of the boat, but maybe it was just filled-up too much or sitting at an angle.

[beast 496]

It is just fuel expansion. The perko vented cap system is great. The vent hose attacthes to the fill neck, similar to an automobile, except the cap is vented. I know you yourself did not fill up the boat, but someone else did. This is typical in the spring as temps increase. Suck out a couple gallons and all will be good. Al