I have a bad habbit of filling my tank way up to the brim. This normally isn't a problem, but the fuel tanks in the CRX's are so small, that I often overfill, and lose a little.

Last night I filled up with gas. I didn't spill any, but as usual, I did top it off to the brim.

This morning it was 30 degrees, and then at lunch time it hit about 60 degrees outside.

Around lunchtime, someone came inside and told me that my CRX was leaking gas bad. I went outside to find that it was dripping out of the filler cap - not a whole lot, but enough to put a small puddle on the ground.

The filler cap was completely closed.. so I oriented my car in a manner where the filler cap would be uphill (rather than downhill, which is how it was when it began leaking) and then I opened the cap to release the pressure (which there was a fair amount of pressure).

We assumed that the gas tank was filled a little too much, and when the temperature was cold. Then during the day as the temperature rose, it caused the gas to expand, and pour out of the filler cap.

Is that even possible?

Are crx's gas tanks vented to prevent this sort of problem? Is there anything I should check, or repair?

Your comments are appreciated.

-Des!

If the weather is like that again just leave the cap unscrewed a little so it can vent but before you take off driving tighten it back up. I assume that would work.

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'93 civic
Brad

OK....I ran into this problem the other day. To answer your question.......

Yes CRXs are vented through a vent line --> one way valve --> charcoal canister --> purge solenoid valve --> finally into the engine.

So the fuel vapors vent through the one way valve and collect in the charcoal canister, then when the car gets turned on the purge solenoid valve opens up and the vapor is sucked into the manifold to get burned.

With all that said , the CRX STILL has a venting gas cap. Even if it's screwed on all the way it will vent into the atmosphere if it needs to. It's possible your canister filled up with vapor, or the one way check valve at your tank is bad so it doesn't allow vapors to vent to the canister.

Something similar happened to me the other day. My vent line is capped at the tank, so I only vent through the cap. I had about 7/8ths of a full tank and I went through my favorite hard right hander. The turn is sick, marked as 30mph and I hit it around 65mph. After going through the turn I smelt gas real bad. I pulled right over and I found fuel running out of my cap!!

So I stopped by my local auto parts store and bought a new gas cap.

Which leads me to me final point. Your cap may be bad. They are supposed to vent, but it's possible yours is old and is venting AND leaking (like mine was). Go change the cap and see what happens they're cheap, mine cost me $11.00. This fixed my problem....so far

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Will do Jadkar.

I knew that you would be able to comment on this since I saw that you did work (twice) to your gas tank.

I will replace the cap... but one thing that still has me baffled is the thought that the car was stationary when the leak occoured.

Some oldschool racers have to know the answer: Is it possible that gasoline would expand during a temperature change enough to travel up the filler tube and leak out of the (potentially) bad gas cap?

-Des!

It might be your fuel pressure too.

When I turbo'd my saturn I used an FMU(horriable idea but thats a different topic) Basically what started to happen is when I would hit full boost I would begin boost creeping. Now It would creepy from 8.5PSI to around 10PSI, this car was also automatic(I know I learned alot about cars since then I swear). Anyway if I would not release throttle and blow off between shifts(like during a race) I would spike to around 12PSI at full throttle.

I found out that if I stopped the car after a hard run and did not drive a few miles or leave it running for a while, gas would start to POUR out of the gas tank once I let off the throttle.

What happened was the fuel was being shot up the filler tube and out the gas cap.

This also was partly due to a horriable design return fuel line from the shop that I had do the kit in the first place(giant mistake always do custom turbo kits yourself or oversee it at all times.)

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2000 Base prelude
AEM CAI
Pspec Shortshifter
more mods coming...

I believe if your tank is filled (or in your case over-filled) the vapor maybe able to force some fuel out of the cap. Think about this. If you have a can of soda and shake it up, when you pop the top vapor (C02) comes out, but so does some soda. The crap gets all over your hand and arm until the pressure in the can equalizes. I think the same will hold true with the gas tank. If it gets bad enough then fuel vapor and FUEL will come out.

The reason I think the cap is bad is because for vapor and fuel to come out of the valve in the top of the cap conditions must be very extreme. Unless.....it's not coming out of the valve in the cap, in my case (maybe yours too) I believe the fuel was coming out of a bad gas cap seal exaggerated by a failing spring which holds the cap tight in place. My beliefs were backed up when after I purchased the cap I found how much tighter it was to screw onto the filler.

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That makes complete sense actually. Thanks guys.

-Des!

ok my response to this is almost the same as jadkar's reponse. On my car ( 90 crx si, b16a) i had the tank out ( again( 9th time)) I took off the one way valve and blew thru the "to tank" hose, and then thru the other way, and it did get some air thru the "wrong" way. This has been a problem for me because i do lose fuel thru the cap on hard right hand turns ( autox and track days), same as jadkar. Now i am replacing the one way valve and the charcol canister ( i think its seen better days) The youngest crx is now at least 15 years old now, and probally 99% of the crxs out there still have the oem one way and charcol parts on them. The only one that probably does not is jadkars beast!! You might want to look into something like this/.
Todd

just a note that liquids don't expand with heat. Gasses do though so if there are pockets of gasses - like in the charcoal filter as mentioned - they could expand and force liquid fuel out.
I always thought the fuel system was fully primed but I learned something here today.

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