my dodge ram 1500 check engine light comes on when I start up and it says gas cap on the dash. I replaced the cap and cleared the alarm and 3 start upslater it came back on
There is a complicated system of vacuum lines, valves and components that make up the vapor purge system on your truck. While the most common problem is a failed cap, there can be cracked or loose vacuum lines, charcoal canister case and other problems with the system. Some can be found with visual inspection but the quickest test for this involves a smoke generator pressure test of the system which will quickly show where the leaks are. A well equipped repair shop will have this tool and can perform the test at a reasonable rate. Good Luck!
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