Chasing down a P0442, I removed the EVAP purge valve to allow better access to the shrader valve while I played with the smoke and the valve. Went to remove the shrader core, put the removal tool down the valve, and it felt 'springy'. Eventually located my reading glasses and, lo and behold, a part of the spring appears to have 'escaped' to the wrong side of the valve as in the microscopic picture below. New failure mode to me, but is this a known failure mode? And I didn't particularly note how tight the green cap was, but could this be the source of a P0442?


The spring escapes...

 

Smoke showed no other apparent leaks. Looking more like the lack of spring force on the shrader valve? Seems odd.

 

Do's the valve leak fuel when the fuel rail is pressurised (with the cap off)
If not it may still be working ok, But looks like it needs changing no mater what...
Good Luck..

 

Didn't check since I took the EVAP valve out once I found the errant spring. It took some care to remove the shrader core without the spring interfering with the operation. I needed much greater magnification for this than my native eyes currently provide sitting next to the car. Once removed, it seemed (as you noted above) that I'm better off replacing it rather than finding the compatible shrader valve. I have not yet found this locally anyway. Just checked for leaks in the rest of the system. Have had intermittent P0442s since I bought the car, which do not appear to be the gas cap.

Don't know who messed up the shrader valve, but probably the previous owner's service personnel? It's hard to believe it unwound itself from the post, but I'm not sure how someone did it. Only thing I can think is that someone went into the shrader valve as it sat on the car with a valve removal tool, blind and awkward, miscentered the tool, caught the bottom of the spring somehow, and just kept twisting (unwound ~3 turns of spring). This despite the fact that this couldn't have felt right at all since the tool wouldn't have seated on the core.

Since the person apparently just left it this way, this also suggested replacement.

 

Have you looked at the locking ring for the evap flange on the top of the fuel tank to make sure it's fully locked..
If its had some work done in the past and wasnt refitted correctly (just a thought)..

 

Good thought. Appreciate it, will check.