Major gas/fuel vapor leak from breather tube at filler neck door - Toyota Nation Forum : Toyota Car and Truck Forums
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post #1 of 10 Old 04-30-2016, 09:11 PM Thread Starter
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Major gas/fuel vapor leak from breather tube at filler neck door

Hi TN,

I have a 2001 Echo 4-door with automatic transmission that is giving me hell. I smelled raw gas fumes coming from the car and checked under the hood and under the car and ended up finding the leak by smelling the fumes right next to the fuel filler door. The car is getting terrible gas mileage (about 26mpg) but otherwise runs just fine.

My husband took the filler neck off and inspected it. No blockage or damage was found. It was reinstalled and the same problem came back. This time we traced the lines back to the charcoal canister and removed it. I have attached a picture of where the breather line connects to the charcoal canister. It is from this port that the raw gas fumes are escaping to the atmosphere. I should point this out: the gas smell *only* occurs when the car is running. If I have been driving it for a few minutes and it has warmed up then it is quite strong. There are no fumes when the car is turned off and cooled down.

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post #2 of 10 Old 04-30-2016, 09:29 PM
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Likely someone has overfilled the gas tank (continued to force fuel into the car after the auto-shut off) to the point it has flooded the canister. Then, when the purge runs the resulting rich mixture is affecting how the ecm responds and screws up your mileage. Your picture is (I think) of the fresh air vent of the canister, which would support my theory. I would replace the canister, DON'T overfill it anymore, and see what that does.

Let us know!
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post #3 of 10 Old 04-30-2016, 09:33 PM Thread Starter
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I habitually top off the tank! Ack. Would you expect the ECM to throw a code for the EVAP system? I can't fathom how the computer hasn't turned on the CEL by now. I have driven the car about 1,000 miles with this fuel vapor leak. Yes, I know it was stupid to drive it.

How confident are you that we will have to replace the canister even with no EVAP code showing?
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post #4 of 10 Old 04-30-2016, 09:39 PM
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Pretty confident, although I don't have time at the moment to explain. I'll try to elaborate tomorrow. But I admit it is a mystery why it hasn't set any codes.
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post #5 of 10 Old 04-30-2016, 10:22 PM Thread Starter
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OK, I placed an order for a new genuine Toyota canister assembly. I will update this thread when it is installed.
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post #6 of 10 Old 05-01-2016, 06:07 PM
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OK, so the canister is the place the car stores any fumes that come from the fuel tank. On almost every "trip," where the car is started and run for a distance, the system purges the canister and pulls the fumes into the engine. The hole you circled is where the system draws in fresh air as the fumes are pulled out. If fumes are coming out, it indicates the possibility that the system has been flooded with gasoline and will never be able to rid itself of the fumes, hence the need for replacement. Once the canister has fuel in it, it's done. That's why you should never pump in more fuel than clicks off the first (or at the most the second) time.

As far as the code is concerned, the only time the system sets the code and turns on the CEL is when it runs a test on the system, called a monitor, and the system fails. In order for that monitor to run, or any of the other monitors, the system has to see a specific set of pre-conditions, different for each monitor, and the car has to be driven in an exact pattern. If the pre-conditions aren't met or the car driven in that pattern, the monitor will not run on that drive cycle. As a result, you can go for any number of drive cycles and the monitor not run. I have seen people who don't drive much on each trip go for weeks without the monitor running. That is one way that your CEL might not have set. Another is there may be a fault somewhere so that the pre-conditions aren't met, like the ambient air temp is reading wrong, which can block the monitor. The point is, it is not unheard of for that to happen.

Finally, if there is a lot of fuel in the canister when the system tries to purge, it'll make the system think it is very rich, causing it to cut back on fuel. If it does it enough, it will adversely affect the way the engine runs and cause your fuel mileage to drop.

Without driving your car while monitoring the system it's impossible to know for sure, but this is all a very likely scenario, leading me to recommend replacement. You may yet have to replace more, but I would start with the canister.

Hope this helps!
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post #7 of 10 Old 05-02-2016, 12:44 PM Thread Starter
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Thanks for your reply, I appreciate it. It was almost certainly my topping off the tank over and over that created this problem. I won't do that again.
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post #8 of 10 Old 05-12-2016, 03:27 PM Thread Starter
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ProTech, you are truly a diagnostic god. My husband replaced the canister and the gas fume leakage went away entirely. The canister assembly came with new hoses and purge valves.

Thanks again!
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post #9 of 10 Old 05-24-2016, 05:01 PM Thread Starter
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Well crap. The gas fumes leak is back. I haven't topped off the tank at all. It came back all of a sudden today after I filled the tank with the auto shutoff for the nozzle at the pump.
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post #10 of 10 Old 05-29-2019, 06:29 PM
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Did this ever get resolved? I’m having the exact same issue.
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