A well-respected mechanic says that topping off the gas tank can cause damage to a carbor filter which is very expensive to fix/replace. Is this true? If true, where is this carbor filter? The emissions system, perhaps?
(Isn’t the filter for the gas pump inlet a simple “breather” or “roughing” filter?)
Don’t know what a carbor filter is, but filling the tank past the hose nozzle’s automatic click-off can damage evaporative control devices (which minimize pollution from fuel vapors escaping the tank) and possibly the carbon canister (which is designed to absorb some of those vapors, but not to deal with liquid fuel). Diagnosing and repairing this evaporative control system can get costly.
There’s a reason for the automatic click-off. Defeating it by continuing to add fuel does no good and may do harm.
I’m sorry, I don’t understand the second question. By “gas pump” do you mean the pump at the filling station or the car’s fuel pump? What do you mean by inlet? The station pump’s inlet is somewhere in its innards. Its outlet is through the hose and nozzle. The car’s fuel pump’s inlet at the bottom of the pump for a tank-mounted pump (which has a “sock” type filter right there) or at the side of the pump for a frame-mounted pump (which doesn’t have a filter, although the pick-up tube in the tank will have a sock filter). What is a “roughing” filter? I’ve never heard the term before. Nevertheless, none of this has anything to do with the components that can be damaged by overfilling the tank.
Modern fuel tanks have baffles inside that keep you from completely filling the tank, so there’s always some air space for expansion. After the filler nozzle clicks off, you can jiggle the car to rearrange the air, and put in another gallon or three, but you’ll never fill it.
On my car, the carbon filter is in a black box attached to the frame next to the gas tank.
Gary T I think the OP is referring to the charcoal inside the evap canister. Charcoal = carbon.
Anyway back to the OP. If you get liquid fuel into the evap canister you will most likely have to replace said canister. I am not sure just how other carmakers plumb their evap systems, but on Volvos there is a roll over valve that prevents liquid fuel to from reaching the canister. This is done mainly to prevent an external fuel leak in the event of a roll over, but has the secondary benefit of preventing liquid fuel from reaching the canister.
As far as where is the evap canister located? No clue since I don’t know what kind of car you are driving. It could be next to the fuel tank, above it, in the trunk, up in the C pillar (the metal pillar behind the side door, and before the rear window), in the engine compartment, you name it. Since this is not an item that gets changed very often, designers don’t always make it accessible. I know of one car where it is necessary to remove the rear suspension to access it. :eek:
Now over the last 10 years or so, evap systems have become more complex with the addition of systems that capture the fumes that come from refilling at a gas station. When you put 20 gallons of fuel into your car, 20 gallons of gas vapor get displaced. In the old days this vapor was just spilled out to the air to create smog. Then gas stations were converted to vapor recovery nozzles on the pumps to capture these vapors. Now proving once again that the gas stations have better lobbyists in DC the requirement is for the car itself to have the vapor recovery system. So to combat the vapor escape carmakers have started putting on board refueling vapor recovery systems. Basically these systems don’t allow the gas fumes to escape out the filler neck, and instead routes them to the charcoal canister(s) so that while driving the vapors can be burned by the engine. The system consists of a fuel inlet at or near the lower part of the tank, large vents at the top of the tank, with floats to seal them off when the tank gets full. The vents lead to the evap canister (probably with larger than normal hoses to handle the volume of vapors) and the canister itself is bigger than normal to handle the extra workload.
I am not sure what you mean by the filter being a simple or roughing filter. The charcoal canister is a box or can full of activated charcoal. Vapors come in one end and are trapped by the charcoal. The other end is (depending on the year and emission requirements in force when your car was built) either open to the air, or goes to a shut off valve or pump that is used when the emissions systems checks if the vapor recovery system is functional.
Now to personal experiences. I have replaced a few canisters over the years for flooding. I could probably count the number of ones I have replaced on the fingers of one hand, and have fingers left over. Not a real common job. Also I have been known to top up my gas tank to where the fuel is standing at the top of the filler neck. I have never had a canister failure. With that said however, the gas pumps here in California warn you not to top off the tank.
So to answer the question asked by the thread tittle, is this possible? Yes. Is it likely? No.
So what would happen such that you would know this device (which I heretofore did not know even existed) required replacement?
Strange way you quoted me there.
Anyway a loaded cansiter will usually cause a strange running (rich) condition. On OBDII cars this should be accompanied with fault codes for the evap system, and maybe fuel trim.
The for sure test is to unbolt the damn thing. If it weighs a ton (like it is full of fuel) it’s bad.
To translate what Rick said, your check engine light will come on.
On a late model car yes. On an early car either no, or maybe not.
Yeah, if the OP had said “carbon” that’s what I would have figured. If he’d said “carbor” once I would have suspected a typo. Using “carbor” twice left me wondering what the heck he was talking about.