bizzs

Hi guys, I have a 2005 Cherokee 3.7l with a p0456. I have been chasing for a fix for about 6 months and I cannot narrow down the fault. I have a snap on scanner, smoke machine and all tools to do the job. I ran a smoke test and noticed a leak around the gas cap. I replaced it with a MOPAR and it sealed some but has a little smoke leak. I ran an evap test on the solus and it passed all test including loose gas cap, purge solenoid and large evap leak. Just for the hell of it, I replaced the purge solenoid with a MOPAR and the code still appeared. I cannot find a smoke leak anywhere within the evap lines. No smoke is visible from the charcoal canister or the vapor leak detection pump. The O ring appears good and no smoke is escaping from that area either One thing that I did notice is I can hear a hissing sound when I pump air into the system on top of the tank but there is no visible smoke escaping from that area.

Is there a pressure relief valve on top of the tank that is allowing the air to escape ? Could this be the cause of that hissing sound? Anyone have thoughts or recommendations?

Thanks
bizzs

97grand4.0

I have found that the filler neck rusts out and leaks. Also could be the hose clamps on the filler neck or the smaller hose that goes to it also. I got a filler neck at the junk yard and it fixed it. But you do have to go through the whole system and check every fitting and hose. Yes there is the rollover valve on top of the tank, the tank itself, and the fuel pump gasket. Lots of fun.