Sometimes it’s as easy as a gas cap that doesn’t seal properly. I can’t remember how man times I’ve told one of our customers: “You’re so lucky it’s just the gas cap not sealing.”

Fixing the gas cap issue is simple. We normally do this in the parking lot as a courtesy to our customers, without even needing to pull the vehicle inside the shop. We just scan the car’s computer, noting that an “evaporative system” code has been logged, which turns on the check engine light. We tighten the gas cap, reset the computer and our customer leaves happy.

However, sometimes the Check Engine Light comes on when there is a more serious issue with your vehicle. The “evaporative control system” handles all the gas vapors so they don’t leak into the atmosphere. This system that has pipes, tubes, clamps, and valves they go from the engine compartment to the gas tank. Finding a leak in this system can time consuming and complex.

Jon, one of our top certified techs, had just such a job recently. He located a tiny leak from a tube on top of the gas tank using a smoke machine. The tube had rusted, and the only fix was to replace the gas tank. Here is a series of images that show just how many devices are in the gas tank and the complex filler tube that was also rusted.