trying to figure out if a P0442 code that has triggered lately is gas cap related before shelling out big bucks for a new one. , i just remembered about a month ago when i was filling up,with gas, with cap in its hole on the filler cover,when pulling cap from hole it came apart and left the spigot part in the cover hole,in the pics below here is what i put back together.part A sits on top of a rubber seal and the spigot part snaps back in the cap body, after lots of searching the web it was mentioned something about a spring came out also ???. anyone know if i am missing a spring, Also there is a gas cap service kit 4G43-68-10936 available, anyone know whats in the kit.. any info would be greatly appreciated..

thank to rich Redpants for pointing me to the cap as my first solution

 

The gas cap is meant to be a vacuum/pressure break. There should be two springs, one to allow tank pressure to vent above a certain pressure and one to allow atmosphere in when the tank is pulling a vacuum. I'm pretty sure you're missing the vacuum side spring allowing the valve to be open under any vacuum.

Check out this image. I know it's from a Ford forum, but the valve in the photo matches almost exactly to your pics. It's probably best to replace the cap. You might try swapping the springs from some other gas cap into yours. Without knowing the evap system vacuum spec it's anyone's guess if that would work properly or not. I think I'd be worried the most whether or not the cap would stay together again. I've never tried to take mine apart to see.

Fuel cap springs

 

thanks GA DB9
as you say best bet would be new cap. pretty sure
this is the culprit ,as i had no codes etc before the cap came apart
the spring could be in the gas tank for all i know, it happened unexpectedly
so wasnt paying any attention to what came apart..
i will try and match a spring as close as i can get in the pic you posted just as
a test to see if it helps until i get a new cap.

 

I would not "try" a spring on the old cap. If it doesn't work correctly your looking @ fuel tank damage. It takes very little vacuum to collapse a fuel tank.

 

J doubleU
duly noted, think i,ll just dig deep in my pocket and get a new cap. grrr