# Fuel fill door and cap off during car wash **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [March 15, 2008, 11:56pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858 "2008-03-15T23:56:33Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![ccb1256](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@ccb1256](https://community.cartalk.com/u/ccb1256)\ **Post date:** [March 15, 2008, 11:56pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/1 "2008-03-15T23:56:33Z")
This afternoon my son left the fuel fill cap off with the fuel fill door open on our 2002 Honda Odyssey after filling the gas tank; and the van then went through a car wash. Is there reason to be concerned that there may be water in the gas tank? ---
**Author:** ![tractorman](https://avatars.discourse-cdn.com/v4/letter/t/e8c25b/32.png) [@tractorman](https://community.cartalk.com/u/tractorman)\ **Post date:** [March 16, 2008, 12:15am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/2 "2008-03-16T00:15:00Z")
There is likely some water in the tank, but the anti-siphon flapper shoud have prevented a large quantity of water from entering the tank. A bottle of Heet, as a precaution, should remove any water in the tank. ---
**Author:** ![SteveF](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/stevef/32/2_2.png) [@SteveF](https://community.cartalk.com/u/SteveF)\ **Post date:** [March 16, 2008, 3:08am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/3 "2008-03-16T03:08:19Z")
We actually get this question asked often, proving there are many other blockheads out there. There really is very little reason for concern. If he was able to drive home then you’re OK. A bottle of Dri-Gas or equivalent will handle the ‘mopping up.’ ---
**Author:** ![cappy208](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cappy208/32/31_2.png) [@cappy208](https://community.cartalk.com/u/cappy208)\ **Post date:** [March 16, 2008, 3:11am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/4 "2008-03-16T03:11:38Z")
other blockheads … OUCH ---
**Author:** ![Beefy\_Norm](https://avatars.discourse-cdn.com/v4/letter/b/a4c791/32.png) [@Beefy\_Norm](https://community.cartalk.com/u/Beefy_Norm)\ **Post date:** [March 16, 2008, 4:26am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/5 "2008-03-16T04:26:45Z")
Fuel filters of today are designed to filter out water content in gas, and remember what happens when you put oil on water: it floats to the top. Fuel is pumped from the (Near) bottom of the tank. Any water that got in will eventually evaporate naturally or because of the gas vapors. ---
**Author:** ![meaneyedcatz](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/meaneyedcatz/32/692_2.png) [@meaneyedcatz](https://community.cartalk.com/u/meaneyedcatz)\ **Post date:** [March 16, 2008, 5:49am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/6 "2008-03-16T05:49:22Z")
Chill SteveF… it’s safe to assume you commited some blockhead acts before. ---
**Author:** ![meaneyedcatz](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/meaneyedcatz/32/692_2.png) [@meaneyedcatz](https://community.cartalk.com/u/meaneyedcatz)\ **Post date:** [March 16, 2008, 6:01am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/7 "2008-03-16T06:01:39Z")
No…gas is lighter than water therefore the water will be in the bottom of the tank. If the van runs bad it should only last for a short time. fyi beefy… gas stations keep a small amount of water in the storage tanks and the pickup tube does not go all the bottom. That way the dirt and junk settle in the water @ the bottom and is not in the gasoline. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [March 18, 2008, 9:25pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/8 "2008-03-18T21:25:19Z")
So, Norm, when the fuel filter filters out the water from the gas, what does it do with the water? ---
**Author:** ![profhandy](https://avatars.discourse-cdn.com/v4/letter/p/b5ac83/32.png) [@profhandy](https://community.cartalk.com/u/profhandy)\ **Post date:** [March 19, 2008, 2:24am UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/9 "2008-03-19T02:24:42Z")
Throw in a bottle of ‘dry gas’. That should do it. “Heet” is one brand but any brand of dry gas will work. If you have electronic fuel injection, a bottle of fuel injector cleaner wouldn’t hurt, either. Just the suggestions from another ‘blockhead’. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [March 19, 2008, 6:30pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/10 "2008-03-19T18:30:39Z")
Gee, Prof, I SO wanted Norm to tell me what the filter does with the water after it separates it out! yeah, I agree, a bottle of dry gas for peace of mind and forgetabout it. The amount of water that likely would have gotten into the tank would be inconsequential. the apray will only hit the valve-covered inlet in short bursts, and any large amount ingested (enough to rise to the level of the pump inlet tube screen) would be felt immediately. ---
**Author:** ![profhandy](https://avatars.discourse-cdn.com/v4/letter/p/b5ac83/32.png) [@profhandy](https://community.cartalk.com/u/profhandy)\ **Post date:** [March 19, 2008, 7:47pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/11 "2008-03-19T19:47:30Z")
My take on what the filter does with water after the filter has filtered the water is that the water freezes in the filter (in cold environments) and the engine won’t run due to fuel starvation. Diesel filters are different in that they have a water drain in them. ---
**Author:** ![NYBo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nybo/32/17281_2.png) [@NYBo](https://community.cartalk.com/u/NYBo)\ **Post date:** [March 19, 2008, 7:59pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/12 "2008-03-19T19:59:06Z")
Even above freezing, a significant amount of water trapped in the filter will slow down fuel flow a bit. But a bottle of dry gas (preferably isopropyl alcohol-based) will clear it out. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [March 19, 2008, 9:47pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/13 "2008-03-19T21:47:23Z")
Guys! Guys! I’m joking! Gas filters in car are particulate filters! Since Norm made the comment that “modern gas filters filter out water” I just wanted to see where he thought the water went. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [March 19, 2008, 10:08pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/14 "2008-03-19T22:08:03Z")
Maybe he thought that it is mixed with the “explosive” nitrogen in the tires in order to defuse the nitrogen. ;-)) ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [March 20, 2008, 5:51pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/15 "2008-03-20T17:51:42Z")
Wow. Two parts hydrogen, one part oxygen, mix in some nitrogen…first thing you know both you and the car argon! I saw a tire on the side of the road. It had in it a puddle of water. Did it used to be a whole car? ---
**Author:** ![NYBo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nybo/32/17281_2.png) [@NYBo](https://community.cartalk.com/u/NYBo)\ **Post date:** [March 20, 2008, 5:54pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/16 "2008-03-20T17:54:39Z")
But the filter material does absorb water, causing it to swell and restrict flow. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [March 21, 2008, 4:13pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/17 "2008-03-21T16:13:39Z")
Interesting thought, does the filter material restrict the passage of water via absorption more than it restricts the passage of gasoline through absorption? I seriously doubt that this is the case, I’d suspect that any hygroscopic characteristic of the fibers would apply to gasoline molecules as well as water molecules, but I’d need to do a bit of research on that. I’ll get back to you. ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [March 21, 2008, 5:17pm UTC](https://community.cartalk.com/t/fuel-fill-door-and-cap-off-during-car-wash/11858/18 "2008-03-21T17:17:00Z")
There are most certainly hydrophilic materials that have an affinity for water but will pass common fuels like gasoline. Gasoline and diesel fuel filters are available with this feature but they are typically much larger than an automotive filter and can be drained. The trouble with these water blocking materials in a common automotive filter is the limited handling they would be able to provide before impeding the fuel flow. There’s no way to drain it off so a small amount would be a blocking condition. Most modern fuels have some ethanol (10%) which already provides enough water handling capability for the expected amount of water in fuel. That would reduce the incidence of nuisance changes. So I guess if a filter was designed with this blocking membrane and it could withstand the pressure differential, it might be a nice feature to have in the event you got a bunch of contaminated fuel.