My 1969 350/350 coupe recently started developing gas tank pressure problems, even though it has a 'vented' gas cap. After about 20 minutes of operation, the gas cap pops off when opened, with obvious internal pressure inside the tank. I tried three different vented caps, and all with the same results. This pressure also explained the gasoline smell coming from the engine, with apparently enough pressure building up to push some gasoline through the needle valves when the car was shut-off.
Any suggests on what I should look for?
Submitted by: TonyC
|
I'm having a similar problem on my 1973. Not only does pressure build up, the fuel gets past the needle valve in the carburetor and fills the intake. The engine has hydro-locked 3 times. I checked the float and needle valve, rebuilt the carburetor, and the problem is still there. The charcoal canister and hoses are connected properly.
It's a safety issue now. Over night the fuel is either being siphoned from the tank or being pushed by the pressure build up. I end up removing the carburetor, pumping the fuel from the intake, and removing the spark plugs to drain gas from the cylinders. I have to change oil each time as well.
I have two 1973 models. One has the problem and the other does not.
|
Jerry Rebman on
3/21/2014 3:58:16 PM
|
|
Thank you all for your replies.
Final solution (that I would up using) was ( per the mechanic that I use was ) to took the vented gas cap apart, removed the spring in it, and re-assembled the cap. So far no pressure build up, fuel smell, or rattles.
It doesn't fix the root cause, which I have not yet found.
|
TonyC on
1/7/2014 8:42:27 AM
|
|
Check thepressure relief valve on the fuel tank inlet. You will have to pull the the inlet/guage sender unit out .It can be plugged by the great gas we have today. also check the pressure relief hose on the rear of the tank.
|
Rev Jim on
5/27/2012 6:15:55 PM
|
|
It's hard to believe your tank builds pressure, but from experience , the gas boiling in your carb comes from the high alcohol content in todays gas, and the exhaust that runs under the carb as a pre heater & causes the carb to get to hot & boil the gas...I pulled the intake and replaced the gaskets and utilized one of the restrictor plates supplied in the crossover port , which stopped the extreme heat from building under the carb !Vic Bellan 57981
|
Victor Bellan on
5/24/2012 1:49:48 PM
|
|
Make sure the exhaust isn't boiling the gas!! Shield, reroute, check for pin holes in the pipes.
|
Terrell Brace on
5/24/2012 9:49:47 AM
|
|
One of the vapor hoses may be pinched.
|
Anonymous on
5/24/2012 8:14:42 AM
|
|
Same problem with my 74.I read were you should not use the gasket on the gas cap. I used to leave the cap loose.
|
Paul Gosselin on
5/24/2012 8:01:34 AM
|
|
Check your charcoal canister...should be lower front left side of engine. If blocked or tubing crimped could aloow pressure buildup in tank, especially as the day warms up from cool nights.
|
Gary Moscowitz on
5/24/2012 7:10:20 AM
|
|
I don't have a solution, but try the C3VR.com forum, Corvette action center forums, and Corvetteforum.com. Somebody should know.
|
Gary Williams on
5/23/2012 1:42:10 PM
|
