For the past week I have been smelling a fleeting odor of fuel in the car. Just this morning the check engine light came on. I checked the gas cap and it did seem loose, so I tighted and will go to the parts store to pull the engine code. Is the any way a loose gas cap would contribute to the smell of fuel in the cabin? A friend of mine mentioned that the smell seemed stronger when standing at the trunk. Thank ya kindly.
It’s possible, but the cap would have to be pretty loose. My guess is that you have an EVAP system problem. The EVAP system is a “closed” system through which the gas tank breaths in and out. It’s “heart” is the charcoal canister.
The canister is simply a path that allows the gas tank to breath in air as the gas is pumped out and forces any fumes that might eminate from the gas tank to vent through an activated charcoal bed. “Activated” charcoal is acid-treated to make in pourous, dramatically imcreasing its surface area per volume. Since carbon bonds very well to carbon, the hydrocarbon molecules stick to the surface of the charcoal in the canister as the fumes move through, becoming entrapped. Charcoal is carbon.
When the engine is started, the “purge valve” is opened and allows the fumes in the charcoal bed to be drawn in by the engine and burned. An engine’s normal operation of the pistons pulling air in for their “intake strokes” creates the necessary vacuum.
While an operating engine normally maintains a slight vacuum in the system, the charcoal bed is needed to allow escape of fumes when the tank is filled and when the gas in the tank expands due to thermal expansion or agitation. Gas, like all matter, expands as it warms, and agitated fluids take up more space than stationary fluids. The EPA requires that virtually no hydrocarbon molecules be allowed to escape into the atmosphere during any of these situations, Thus, the fume-catching charcoal.
If you’re in the habit of “topping off” your gas tank, you may want to discontinue the practice. Some systems can allow gas to go through the vent line to the charcoal bed and saturate the charcoal. That can smell.
You’re correct. The dtc I pulled was p1456 (leak detected in evap control system (fuel tank system)) according to my service manual. The light just came on this morning and tank is about 2-3 gallons away from empty. If it was the cap then I presume that the code will clear once the system recognizes things are clear or should I clear the code manually? If the charcoal has become saturated, should take measures to correct it or just allow it to work itself out?
If by “topping off” you mean adding alittle more fuel beyond the auto stop point of the pump, then yes I do that rather frequently to round the cost of the fill up. This last fill was prolly a bit too much and I’m not surprised the element you mentioned may have gotten saturated. Why it occurred this time and not previously I can not say.
I’m unaware of any way to dry a saturated charcoal bed.
The code you read may have been the result of the loose gas cap and if so it’ll clear itself. The gas smell might have been from the canister.
Now that you’ve resecured the gas cap, if it were mw I’d just see if the code clears itself and if the smell goes away. And I’d discontinue adding that extra gas after the hose stops.
If the light does not reset you’ll want to look at the canister. If the bed is saturated, the tank won’t be able to breath in as gas is pumped out. A vacuum can develop in the air space in the tank and that can overstress the fuel pump and lead to premature pump failure.
f by “topping off” you mean adding alittle more fuel beyond the auto stop point of the pump, then yes I do that rather frequently to round the cost of the fill up.
Yea, that will do it. Likely there is a note in your owner’s manual or on a sticker somewhere on the car, telling you not to do that.
I read that it may reset after so Many miles or and/or after the next tank fill. I hope the charcoal bed isn’t saturated as that sounds kind if annoying to restore.