evap prob

my blazer keeps turing on the mil for a p0442 evap leak at first it thought gas cap so i bought a new one same problem and this week i noticed it only comes on when my gas gauge is on about half tank ive filled it up and done warm up cycles cool downs and nothing till i get a half tank than boom mil shows up

beating a honda is like doin a fat chick you just dont brag about it

LMAO:lol:

check all EVAP hoses going to and from the charcoal canister.

Its coming on around 1/2 tank because the EVAP self test will not run until there is about 1/2 tank of gas. As BlazerLT said look for any loose connections at the Charcoal canister. On my 96 2dr 4x4 it is behind the drivers rear wheel. There is also a vent valve that is electrically controlled (solenoid) that needs to open and close. Open to vent the system and closed when running the EVAP test. Mine was located up between the rear axle pumpkin and gas tank. You can remove it and blow through the passages, then put 12 volts dc to it and blow through it again one way will be open one closed. If it is not closing that could be your problem. Min looked like this, there may be 2 versions though.

http://catservices.wrencheadpro.com/smartpages/partinfo_resize/KEM/162-440.jpg

had the same problem on my 97 LS 4.3L 4WD. Turns out the solenoid going to the evap canister was bad. New one put in and no more problems. Check that solenoid for sure.