Gas Tank Vacuum

[Mystic ZR-1]

Seems like there's a lot more vacuum then normal
when removing the gas cap? 1990 w/40k miles

No codes, runs fine. Always has passed emissions where they check
gas cap as part of check.
Fuel level in tank makes no difference.
None of the hoses/wiring etc have ever been messed with.
Just replaced fuel pumps, but it did this previously.
Gas cap?
Evap cannister solenoid valve?
Imagination?

[BigJohn]

Originally Posted by Mystic ZR-1

Seems like there's a lot more vacuum then normal
when removing the gas cap? 1990 w/40k miles

No codes, runs fine. Always has passed emissions where they check
gas cap as part of check.
Fuel level in tank makes no difference.
None of the hoses/wiring etc have ever been messed with.
Just replaced fuel pumps, but it did this previously.
Gas cap?
Evap cannister solenoid valve?
Imagination?

Air temperature and air pressure!

What is kind of scary is when the fuel blows out with air pressure change!

It happens just not often!

[Dynomite]

If you disconnect the Fuel Rail Fuel Lines, ALWAYS remove the gas cap or you will get a continue dripping of fuel out of the fuel lines as long as they are disconnected from the fuel rail.