If the rear differential was worked on, it could have affected the system if the lines are kinked or bent too much.
Check the areas around the fuel tank for any interference to EVAP lines.
When no trouble codes are present, it should not be a fault with solenoids or electrical components. The lines are for pressure release and fumes control and is usually dry. Cleaners might not work as the lines are from front of vehicle to rear so it could be quite long.
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Wednesday, January 19th, 2011 AT 5:25 PM