mds3013

Photos of bladder in a '77 tank before I throw it away. Just showing what is inside.












From an old tank I picked up. mike...

AdamMeh

Have been wondering what the bladder in our '77 looks like. What are your plans? Did you get a used tank, or are going replacing with a new?

Adam

mds3013

This is a bladder from a wrecking yard find. My original is in the car still.
What I did find was that the vent line on the top of the tank was not tapped into the bladder. mike...

AdamMeh

Wow... so the vent wasn't working, and the cap was a non-vented type from the factory?

mds3013

Vent was set up that way from the factory. All penetrations into the bladder went through the sending unit. The vent I referred is on the left in this pic. on the side tap of the tee. Venting the area between the bladder and the steel tank. mike...

AdamMeh

Ah! Great info. So it's a vent that allows the bladder to expand etc. Thanks for sharing this Mike.

Adam

DUB

NO... The VENT does not allow the bladder to expand. The fuel cap allows air to be drawn into the fuel tank AND the fuel evap system is drawing air from the fuel tank and also the area between the fuel tank and the bladder....becasue they are joined. This keeps these two spaces balanced and one is not pressurized more than the other.

The fuel cap must allow air into the fuel tank or it can actually get have so much vacuum on it that it collapsed like a crushed soda can.

Does this make sense.

And what happens over time...due to fuel sloshing around and people really topping off the fuel tank...is that the vapor line for the EVAP system gets plugged up with fuel and it turns to varnish and plugs up this line and thus the EVAP system can not pull air from the fuel tank...and knowing that the fuel cap will not allow pressure to pass by it ( or should not)...the fuel tank can NOW be pressurized. Which is not a good thing if it gets to high.

DUB