Gas Cap Questions

[MikeCT]

How can you test if your gass cap is holding a vacuum? If the gas cap leaks is this / could this cause problems? Just wondering.

[swimmingly]

I believe any place that does a smog check has the tool that can hook up to your gas cap and check if it's able to hold the right amount of pressure.

[Pike]

Is a pressurised tank nessesary? My cap was rusted through and leaked on the hard corners. I noticed no difference when I got a new cap. (that dosen't leak)

[Paul Glasson]

When you talk about the gas cap, presume you refer to the cap for filling petrol. You don't want a vacuum there it could cause petrol starvation.I doubt Positive pressure will hurt much unless it builds up too much to blow rubber hoses etc. The seal should be mainly to help prevent evaporation of petrol.

[MikeCT]

Vacuum was not the correct word. I mean pressure from the tank.

[SoCal Driver]

Originally posted by Pike
Is a pressurised tank nessesary? My cap was rusted through and leaked on the hard corners. I noticed no difference when I got a new cap. (that dosen't leak)

It isn't the cap that is leaking. It's the short piece of hose that connects the filler tube to the gas tank propper. Also the small vent hose cracks and leaks too.

[SoCal Driver]

Originally posted by Paul Glasson
When you talk about the gas cap, presume you refer to the cap for filling petrol. You don't want a vacuum there it could cause petrol starvation.I doubt Positive pressure will hurt much unless it builds up too much to blow rubber hoses etc. The seal should be mainly to help prevent evaporation of petrol.

Here in the states the gas tank is sealed and the fumes are scavaged into the engine intake. So the seal on the filler cap is tested -- I think for a vacuum.

[MikeCT]

Originally posted by SoCal Driver
It isn't the cap that is leaking. It's the short piece of hose that connects the filler tube to the gas tank propper. Also the small vent hose cracks and leaks too.

How hard is it to get to the vent hose. I was looking through the factory manuals it says you need to take the side window out. Is there another way to do it?

[TCMdocs944]

Just read a post that says the quarter windows are exceptionally easy to remove.

[SoCal Driver]

Originally posted by MikeCT
How hard is it to get to the vent hose. I was looking through the factory manuals it says you need to take the side window out. Is there another way to do it?

You can bend up the inside trim panel but the best way to get to the filler cover is to do the proper thing and remove the side window or you may tear the trim.

I've cut my trim so it just slides under the inside of the window rubber seal and not over the edge of the body work. Stays in place nicely. Also have less problems re-sealing the window.

the most likely leaking point is the small vent hose. You can cut it and put a 45 degree copper tubing elbow in and clamp it. That way you don't have to drop the gas tank.