I dont mind if some water gets in it make the helps fill the tank. Hey I should list that in the free mods section.

 

I know this thread is a bit old, but I wanted to pass along an easy fix for this problem for others to use.

My 2006 Silverado started showing the Tighten Gas Cap light on my dashboard after I took a long trip in the truck. Up until this point, I've never had any warning lights with this truck. I've heard of this problem with other car/truck owners, who had less than satisfactory outcomes. Naturally, I tightened the gas cap about 20 times, but no luck. I examined the gas cap, and it looked fine. I read my owners manual, that basically told me that the warning light (orange indicator) should go out after a few key starts. After tightening the gas cap, it would go a few days, but sure enough the DIC warning would appear again. Eventually, the warning light (orange) did clear, but a few days later, I would get the "tighten gas cap" DIC warning again and then the warning light (orange) would lock in.

Consequently, I was dreading taking my truck back to the Stealership, so they could dream up more problems and hand me a bill. As a last ditch effort, I bought a Haynes manual and read about the Evaporative System on my truck. The gas cap DIC warning is part of the evaporative system to reclaim gas vapors. The onboard computer on the truck monitors the gas tank vapor pressure, which checks for vapor leaks in the fuel system. The warning involves a pressure mismatch, which the onboard computer relates to a fuel vapor leak. It assumes fuel vapors are escaping via your gas cap thus circumventing the purpose of the evaporative system.

I fixed the problem by dipping my finger into cap full of motor oil and applying the oil to the gas cap gasket. Poof! Problem solved. The gasket on the gas cap gets dry (probably due to overfilling the gas tank once) and over time the seal drys out. By re-lubricating the gas cap gasket, it once again seals properly. If the gasket on your gas cap is torn, or cracked, then get a new gas cap.

 

I fixed the problem by dipping my finger into cap full of motor oil and applying the oil to the gas cap gasket. Poof! Problem solved.

You know sometimes the simplest solution is the best.....I didnt even think about that.....and I too have had to do that

 

There may be a leakage on the tank.

 

what light is the check gas cap light??

 

There is a check engine light, and a "Tighten Gas Cap" DIC warning message, but not a "Tighten Gas Cap" light. Sorry about the confusion.

 

I just read all the post concerning the fuel problems. I have a '04 Chevy Avalanche and I'm getting a signal saying "tighting the fuel cap". I brought a fuel cap and it still saying the same thing. Now, when i take the cap off a "hissing sound" come from the gas tank then stops after about 1 minutes. Can somebody give me some insight on what this problem may be and how it can be fixed without going to the "stealership".

 

This is the exact same problem that I am having with my 2004 Chevy Avalanche. I took it to the dealership and when the service manager (the same one that I have used for the past 6 years) took the cap off and my truck hissed at him, he said, "WOW! I've never heard that before."

Does anyone have this problem and more important -- the solution

 

Anyone determine what the problem was with their fuel system? I have the same problem with a 2004 Suburban. Wondering if it is a fuel pump issue. It also has a difficult time starting now on occasion since the tighten full cap message started appearing, even though we replaced the fuel cap. Same high vacuum issue in the tank as well -- if we drive it a while between fill ups, there is a lot of vacuum in the tank, causing that whooshing sound when you take the cap off.

Thanks,

Matt

 

Unfortunately, my "oil on the gas cap gasket" fix didn't work for very long. I eventually had to bring my truck back to the Dealership and have it fixed. It turned out to be a problem with Evaporative Emissions Solenoid, which is part of the fuel system. This solenoid is a known problem with older (2004-2008) Chevrolet and GMC trucks & SUVs. The dealership replaced my solenoid with a later version (ver. 3.130) and I have not had any problems since.

If I can be of any additional help, let me know and I'll help where I can.