The other day I walked out to my car (91 Civic Hatch, base) to discover fuel bubbling out of the cap. I took the cap off and a lot of fumes vented. I've never had this happen before, occasionally when I go to fill up and take the cap off it will vent a little bit, but I've never had gas bubble out like this.

I did some research and it seems that my charcoal canister might be plugged up, or the two way vent valve allowing the fumes to travel to the canister might be failing.

My question is, as a first step to attempting to solve this, can I just remove the charcoal canister? I've come across several old threads discussing this but haven't been able to find any with pictures of exactly how to do it.

I'm getting pretty terrible mileage right now (20-23), could excess pressure building in my gas tank be part of the problem or is it unrelated?

 

Fuel bubbling from the cap is strange, but yes, you can disconnect the "fume" line from the canister as a first step and see if that corrects it. Don't bother removing the entire canister setup until you know.

You will see a red hose coming from the firewall which connects to the canister, just disconnect that line. It's the line that allows excess tank pressure and fumes to vent into the canister and get absorbed. Keep in mind that disconnecting this line will vent the fumes to atmosphere, so you may smell gas in and around your car.

 

Not to hijack the thread, as this may also help solve the problem the OP is having.. If you disconnect that line, could you technically just run a filter to the red hose and delete the charcoal canister? I'm looking to remove and clean up all of the excess vacuum lines on my EF hatch for when I put in a vacuum manifold.

Is there a simple delete for the canister?

 

Remove and cap the manifold and firewall map sensor hose port. It will smell like gas at start up though.

 

It will likely smell like gas most of the time. This is similar to having a jerry can with a lid that doesn't quite seal. Warm weather will cause the air in the tank to expand and will push fumes out of any opening.

 

^ If you ran the vent hose down near the wheel well/shock tower and put a filter on it do you really think it'd be that bad?

 

That would help, at least while driving. If you store your car in a garage it won't make any difference.

Any update on fixing your issue?

 

I haven't had any pressure issues since disconnecting the hose from the firewall to canister, but I'm going to reserve judgment until after I fill up again.

 

I filled up with gas yesterday afternoon and when I walked out to my car an hour ago there was a nice puddle of gas where it bubbled out from the cap again! I'm seeing a pattern here: fresh tank + warm the next day = bubbling out of cap. I can't even smell a whiff of gas from the tube that runs from the firewall to the evap canister.

I'm going to be under the car next week taking the cat off, how hard is it to get to the valve that lets fumes travel from the tank to the evap canister? It seems almost certain that it's failed.

 

It's hiding under a plastic cover bolted to the drivers side of the fuel tank. I remember on my EG the bolt to remove it was on the top, so loosening it was tricky. Unfortunately this one kinda looks like phillips screws to me.

It's this red thing:


Just be careful not to break off any nipples when removing the hoses. Old plastic gets brittle. Also this valve is not available from Honda any more so your only option for replacement is used.

To test it, just gently blow into either nipple. It should allow air to flow in both directions.

If your 2-way seems fine, consider replacing your gas cap. Gas caps also have an emergency vent valve inside that are supposed to vent at a much higher pressure than the 2-way valve. If the fuel cap is venting before the 2-way, you could possibly get this same spillage.

 

Thanks for the tips.