2002 vapor valve leak on fuel tank

Texas Hot Rod

Texas Hot Rod

1955, 56, 57, 02 T-Birds
Last seen
Joined
Jul 26, 2022
Thunderbird Year
1955
My 2002 T-Bird has a leak on top of the fuel tank where the vapor valve is located. Has anyone had any luck sealing this to stop the EVAP codes? A smoke test revealed the leak.
 

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Does your Check Engine light come up on dash? A trick I learned is to keep your gas tank above 1/2 full and the light will stay off. I've had this vapor leak for over 4 years and there is no other issue with it.
 
My 2002 T-Bird has the same problem. I have changed the gas cap out once & it was suggested I do it again. My 'check engine' light would come on sporadically but now has been on constantly for the last 6 months with any amount of gas in the tank. Thanks to your question, at least now I know a smoke test should be a relatively easy way to diagnose the problem.
 
It's possible that the rubber grommet that holds the vapor valve into the tank is probably cracked. Dropping the tank with a low fuel level is not really difficult, a new grommet and maybe hoses seem like an easy fix.
 
Issyro said:
Does your Check Engine light come up on dash? A trick I learned is to keep your gas tank above 1/2 full and the light will stay off. I've had this vapor leak for over 4 years and there is no other issue with it.
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I'm surprised that by keeping the gas tank above 1/2 full the light will stay off. According to the Ford Motor Company Driving Cycle, the fuel tank should be between 1/2 to 3/4 full so the Evaporative Monitor will operate. It's possable thaat either you performed the Evaporative Monitor bypass or the level in your fuel tank was above 3/4 full.

doug7740
1955 Thunderbird Blue

Drive Cycle 1.jpg

Drive Cycle 2.jpg
 
In my case the fact is true, the code (P0442) is what I read when my Check Engine light comes on, I clear it and it will not come back till the tank is mostly under 1/2 full. After four years of this I know that it works for me.
 
I could not find the valve, drop the tank and were the crack was at cleaned and sanded and put the same glue used to hold wind shield in. So far so good..
 
Thank you to all that replied, it was a great help! Turned out to be a cracked valve. We sealed up the crack with some Q-Bond Adhesive. Hopefully we won't have any more problems. See attached.
02 T-Bird Fuel Tank Sketch.jpg
 
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Trying not to hi-jack a thread, so started this one.
Moderator note: Your are more likely to get an answer by replying to a thread that is exactly the same problem rather than creating a brand new thread. As a matter of fact, someone already stated how they fixed your problem. Post merged.

Seeking knowledge on the fuel cell (tank) composition, is it HDPE or some other plastic? I’m fairly sure I have a fuel leak at one of the vapor valves on the top of the tank. I removed the shelf behind the seats to reveal the top of the fuel pumps.The pump seal rings are fluid tight and not leaking. The leak is coming from the very tip top of the tank and then running down to the fuel pump access level. There are no apparent leaks with the car running and It only leaks when the tank has just been filled. After it leaks down (tank level gauge still reading full) then the leak stops. I’m confident the vapor valves are therm-welded and not set in grommets. The only permanent fix, I know of, is to melt some new HDPE plastic or replace the entire tank. Either way it’s a big job. Seeking the cheapest fix possible.

Oh, I tried to run a bore scope on the tank top, but had little success. A little more info, it has not thrown a code yet. I also read that a member sealed a similar leak with Q-Bond. Any ideas??
 
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Oh, here’s something for the gear heads on the site. I took my ‘02 to my mechanic today. It’s a challenge!

Here’s my symptoms:

Given: Recently changed electric fuel pump.

1. Very slow to fill gas tank. I mean really slow!
2. Leaks from top of tank when full. (Car not running)
3. Stops leaking after a few minutes.
4. It doesn’t leak from fuel pump flange seals.
5. Doesn’t leak while car is running.
6. Over 300 miles on this tank of gas and hasn’t thrown any codes. Went from full to less than a quarter tank of gas.
7. Runs smooth and as strong as ever.

Question: You be the mechanic, “What is broken? Take your best shot as this?

I will post updates as soon as the shop identifies the problem. Let‘s see who gets it right.
 
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The fact that you said that it is really slow to fill the fuel tank and there are leaks from the top of the fuel tank when full and the car isn’t running, would lead me to believe that you have either a defective fuel vapor control valve, fuel vapor vent valve or a fuel saturated evaporative canister.

Here is how the system works:

The fuel vapor control valve controls the flow of vapors out of the fuel tank by closing when liquid level reaches a height associated with the fuel tank usable capacity. This limits the total amount of fuel that can be dispensed into the fuel tank. Fuel vapor tubing connects the fuel vapor control valve to the evaporative canister. This routes the fuel tank vapors that are displaced by the incoming liquid to the evaporative canister.

Between refueling events, the evaporative canister is purged with fresh air so that it may be used again to store vapors accumulated during engine soaks or subsequent refueling events. The vapors drawn off of the carbon in the evaporative canister are consumed in the engine.

doug7740
1955 Thunderbird Blue

Fuel Tank.jpg
 
Thanks Doug, this gets more puzzling by the minute. My mechanic said come pick up the car and come back when you have a new fuel tank. He said the tank is staying pressurized and won’t vent. The puzzling thing now is I have a P0455 Large Evaporator Leak pending code. I don’t know when this code triggered, I’m assuming when the pressure test was done. Ok, a pressurized tank with a leak code??? I’m beginning to lean toward an evaporator canister blockage or the evap vapor vent stuck shut. I think this normally open vent is on the canister outlet so regardless of vent position, if the canister is clogged the tank will not vent. I still struggle to understand the overfill fuel leak situation. What am I missing?
 
We know that the fuel tank won’t vent because you said that it is really slow to fill the fuel tank. It seems like your mechanic believes that your problem is caused by a defective fuel vapor control valve.

The fuel vapor control valve assembly is mounted on the top of the fuel tank. It is used to control the flow of fuel vapors entering the evaporative system. The assembly also has a spring float, which prevents liquid fuel from entering the vapor delivery system under severe handling or vehicle rollover conditions. In the upright position, the open bottom of the float will lift and shut off the orifice. Under severe handling conditions, the spring will push the float closed when angles allow liquid fuel to reach the orifice. In a rollover condition, the weight of the open bottom float and spring pressure will close the orifice. The valve cannot be serviced separately; a new fuel tank must be installed.

If you believe the evaporative canister is blocked you could disconnect the vapor tubing at the canister and if the fuel tank fills normally then the evaporative canister is definitely blocked. If the fuel tank stills fills slowly with the evaporative canister vapor tubing disconnected, then fuel vapor control valve is defective and the fuel tank will have to be replaced.

doug7740
1955 Thunderbird Blue
 
I’m totally in agreement with your diagnostic and already have a replacement fuel tank coming. I still cannot visualize the actual source of the leak.
i might also think a good rap with a rubber mallet to the tank might reset the spring float an allow it to go back to its normal position. I vaguely remember the first time I smelled fuel leakage was a time leaving a parking lot and the car dipped abruptly. Basically, it sloshed the tank really bad and could have stuck the valve closed. Since I’ve already ordered the tank, i will start from there. Thanks for sharing your knowledge.
 
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doug7740 said:
We know that the fuel tank won’t vent because you said that it is really slow to fill the fuel tank. It seems like your mechanic believes that your problem is caused by a defective fuel vapor control valve.

The fuel vapor control valve assembly is mounted on the top of the fuel tank. It is used to control the flow of fuel vapors entering the evaporative system. The assembly also has a spring float, which prevents liquid fuel from entering the vapor delivery system under severe handling or vehicle rollover conditions. In the upright position, the open bottom of the float will lift and shut off the orifice. Under severe handling conditions, the spring will push the float closed when angles allow liquid fuel to reach the orifice. In a rollover condition, the weight of the open bottom float and spring pressure will close the orifice. The valve cannot be serviced separately; a new fuel tank must be installed.

If you believe the evaporative canister is blocked you could disconnect the vapor tubing at the canister and if the fuel tank fills normally then the evaporative canister is definitely blocked. If the fuel tank stills fills slowly with the evaporative canister vapor tubing disconnected, then fuel vapor control valve is defective and the fuel tank will have to be replaced.

doug7740
1955 Thunderbird Blue
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Monday, I am having the fuel tank replaced. I have a question in regards to the evaporator cannister. Is it something that may need replaced while the tank is down? I wouldn’t want to drop the drive shaft again if it is needed to replace the cannister later. It may be accessible without dropping stuff. I have heard on a 2002 Lincoln LS, you must drop the subframe to get to the canisters. Is anyone familiar with an 02 Bird?
 
According to ALLDATA if the evaporative canister is being removed the subframe must be removed. The subframe does not have to be removed when replacing the fuel tank. The labor time to replace the fuel tank is 3 hours.

doug7740
1955 Thunderbird Blue

Canister 1.jpg

Canister 2.jpg

Rear Subframe.jpg

Fuel Tank Labor.jpg
 
Got everything corrected today, and the bird is back on the road. The leak from the tank overfill was coming from a crack in the seam on the vapor valve, not at the tank/valve plastic weld. The other problem of not being able to fill the tank was not related to the Carbon canisters or the evaporator vent. The tank wouldn’t fill due to FME in the tank fill line. A piece of plastic was blocking the fill line at the antI-siphon screen. A borescope and a grapple wire remedied that problem. All is well now.
 
My 2003 Bird is currently in the shop and has been for almost two weeks. The main problem being it won’t pass inspection because of fumes leaking from the top of the fuel tank. There is a crack in the gasket, which they no longer make. They have gotten two used tanks to replace mine. They both have the same problem. Has anyone else encountered this problem and if so, how did you resolve it?
 
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