Gas leak

ALLENE SIMS

MEMBER
2018 TOYOTA RAV4
4WD
AUTOMATIC
40,000 MILES

I purchased the car listed above pre-owned, and noticed a strong gas smell after about 3 months. The smell was more pronounced when the weather was exceptionally warm, and a couple of times there was gas that had leaked out into the driveway. My mechanic was at a loss, and suggested I take it elsewhere for a smoke test and report back to him. The report indicated that the car needs a fuel vent tube and carbon canister. It also indicates that the only way for fuel to get into canister is a defective overflow valve internal in tank and so the car needs a full fuel tank and canister replacement. My mechanic is apprehensive because he finds it hard to believe this would be necessary in such a new car. I’m hoping for some guidance on this, and if a full fuel tank replacement is necessary.

Tuesday, March 2nd, 2021 AT 8:15 PM

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

This is not entirely true. If it were me, I would not replace the fuel tank as fuel can get into the canister if the person filling the tank tops off the tank. Meaning when they are filling it with fuel and the nozzle shuts off the first time that they continue to click more fuel into the tank.

This nozzle on fuel pumps is designed to sense when the fuel vapor is increasing in pressure which means the tank is fuel and it shuts off. This is meant to leave a small area in the top of the tank for proper venting of vapor off the top of the fuel into the emission system (canister and purge valve) and allow for any expansion of the fuel when the temperature changes.

So when you fill the tank until this vapor gap at the top of the tank is taken up with fuel the only place it has to go is into the canister and up the fuel filler neck. So when the purge opens and pulls in vapor from the canister, like it is supposed to, it pulls raw fuel instead.

What happens is when the canister gets raw fuel in it, the charcoal breaks down and it causes the purge to stick which is where the fuel smell is most likely coming from.

I would replace the canister and the purge valve and then retest this. However, I suspect it will take care of the issue.

Let us know what you find. Thanks

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