Vacuum Forming in Fuel Tank?

[Shaun P.]

[Bill M.]

Re: Vacuum Forming in Fuel Tank?

This has happened to me 40 years ago the 65 was stalling out after a couple of miles. After a few times I noticed that when I would remove the cap to check for fuel I would hear suction. I finally drilled a small hole in the cap and that was it. I don't think I ever changed the cap.

[Edward J.]

Re: Vacuum Forming in Fuel Tank?

Shaun why not buy another cap for test reasons there not that much, and keep the original and store for judging reasons. I know years ago I remember always hearing pressure releasing when removing the cap more so with the heat and movement of gas while driving.it is a a sealed system to recover vapors and recycle back into engine.

[Shaun P.]

Re: Vacuum Forming in Fuel Tank?

I did so yesterday Edward. Posted here moments before in an effort to get ahead of the problem and to document in my notes any actual or known issue I can. Thanks for the time.

[Tom R.]

Re: Vacuum Forming in Fuel Tank?

This is when you need a 1982 Corvette Shop Manual! There is little comparison to Corvette emissions that preceded that particular model year yet some inferences can be made given the fuel vapor emission control devices were similar from the early 1970s up.

Let me take a look and see what I have around here.

Ok, my first suspect is the fuel vapor solenoid. But I'm guessing based on what you describe...its all original. But electronics fail after what some 40 years? The schematic shows the solenoid control, what appears to be the firewall on the driver's side. Follow the hose from the PCV valve...it leads to the solenoid. The manual reads this in the engine emission control section:

Page 6E-13: Evaporative Emission Control System (Fig 6E-22)
The ECM (electronic control module...the engine computer) controls the vacuum to the purge valve in the charcoal canister with a solenoid valve. When the system is in open loop, before a specified time has expired and below a specified RPM, the solenoid valve is energized and blocks vacuum. When the system is in closed loop, the solenoid valve is de-energized and vacuum can be applied to the purge valve. This releases the collected vapors in the intake manifold.

It doesn't show or describe how to test the solenoid and whether its functioning as intended. But, someone has been through this stuff...perhaps here or on the Corvette Forum. You may need some diagnostic tools, or figure out how to read the codes from the ECM, which are listed in the shop manual. There are a number of schematics shown here but if you plan to drive and enjoy that 82, it may be worth the investment to track down the shop manual.

Hope this helps and let us know what else you may need!