1985 Buick Syklyark - Excess pressure in gas tank?

Hi gang....
This stared all of a sudden. Shut the engine off. Then it would not start again. Fuel pouring out onto the ground from behind the fule pump. This is a 6 cylinder motor with the pump up front.
Quickly I ran back to the filler cap to help stop the gas from gushing out. When I did, the air escaping (or coming in?) sounded like a set of air brakes. Wow!
Went to the parts store and made sure that I bought the specific gas cap for this car. Same problem with gas gushing out after the car has been warmend up and then shut off. Same air rushing from the cap when I unscrew it.
Went through the whole procedure again, this time with no cap on at all. When I shut down the engine, no leaks.
So the car runs, stops and starts fine with no cap.
What should I be looking for in this situation?
John
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
@budweiser.com says...

Sounds like your fuel line check valve is faulty, causing your fuel pump to pressure your fuel tank. The check valve may be built into the fuel pump.
Not specific but a general overview: http://autorepair.about.com/cs/troubleshooting/l/aa042603a_03.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
@swbell.net says...

http://autorepair.about.com/cs/doityourself/a/aa050701a.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That is interesting KS, but this appears to be purely mechanical, since its bolted into the side of the engine. I suppose that there is the same type of check valve on a mechanical pump? If so, does this look like a scenerio where I should just change the pump?
Thanks for replying.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
@budweiser.com says...

I would recommend replacing the fuel pump and it would also be a good time to replace your fuel filter too.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Check the solenoid on the vapor cannister, this is attached to the tank lines to release vapor pressure into the intake system

-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
My El Camino did the same thing, the vent line was rusty, and plugged, other tubing good [ full of fluid all times ] Replaced vent line with rigid plastic tubing, all is fine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for the replys guys. Will check it out this week.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.