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'02 Impala 3.4L 195.4k: Replace Factory Gas Cap Gasket?

How do they test the fuel tank for vapor leaks on a 1993 vehicle?

They do two tests. First , they just test the gas cap to make sure it is air tight. They have a gadget they screw the gas cap on, then they pump it up with compressed air and make sure it doesn’t leak down. The other thing they do is when running the car on the treadmill for the tailpipe test they screw a special test fixture to where the gas cap would normally go. What exactly that accomplishes, not sure, they may be injecting some special test gas into the fuel tank, or testing the fuel tank it air tight. I know when they do that test they clamp off the purge line from the charcoal canister to the throttle body.

That sounds like a lot of work, we just do a visual inspection on the cap for pre-1996 vehicles.

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In California things like this are never done in a simple way … lol …


No. I retired and had to get a new Subaru for my wife. She doesn’t drive anymore but with limited range of motion on one leg, the Subaru was the only vehicle she could get in and out of. So with a new car and still having my truck, and being retired, I didn’t see the need to keep it. Sold it at 275k miles, still running like new, and the body was still tight as new, no squeeks or rattles.