Today I solved my Evap problem. First I though it was the aluminum fuel filler tube (mine was not completely round where the cap fits on) so I replaced it with one from Pick N Pull. Luckily the filler tube is the same for many Volvo's for many years, didn't seem to matter that mine was a wagon, I just compared the part number on mine to the junkyard car.

Unfortunately the better filler tube didn't help pass the Evap test. The smog guy suggested I find a shop with a "smoke tester", a device thats injects low pressure (1.5 PSI) smoke into the tank system, then you look for leaks. "where there's smoke, there's a leak".

A friend of mine owns a VW repair shop, he normally would never work on Volvo's but let me use his smoke machine. In 5 minutes we found the leak, it turns out one of the rubber hoses on the charcoal canister came off of the hard plastic line that eventually goes back to the gas tank. We couldn't see that the hose was off the line because it was under the air cleaner box, but the smoke was visible. After we pulled the air cleaner box it was really obvious where the problem was.

This is the smoke machine he used, Redline Total Tech http://www.redlinedetection.com/products.htm at $1000 it's not cheap enough for the home mechanic, but many shops in California are getting them. I thought it was interesting that the machine generates smoke using baby oil from any drugstore.

Bottom line, my car has passed the smog test. The photo below shows the rubber hose that came off the hard plastic line. (Air filter box removed). If you fail the evap test you can remove your air filter box and check the lines underneath it.