Now that it's very hot out here in Vegas, I'm noticing a significant fuel odder. After checking extensively for leaks, and finding none, I started looking at the EVAP charcoal canister on the fire wall. It appears that after a hot drive, the car has a bunch of fumes coming out of the fresh-air tube connecting to the bottom of the canister. There is no wet fuel in or around, but I can definitely see wavy fumes wafting out of the tube under the car (I can catch them with my hand). I always thought that was tube was ONLY a fresh air intake (one way) and that fumes should not be able to come out this way. Does anyone know how to fix this?

 

For those that search this problem in the future I found the following link. Another person in Las Vegas had the exact same symptoms as I did with his 92 Accord (now I have it on two cars 94 Civic & 89 CRX). The problem seems to point at the EVAP 2-way valve on the fuel tank. I popped mine off the 94 Civic and cleaned it out with some QD electronics spray cleaner (safe for rubber & plastic). Seems to help with the 1st warmer day. We'll see when I drive it Tomorrow as it will be ~105 outside.

This valve is on the side of your fuel tank underneath a plastic cover. It is accessible from under the car without dropping the tank EGs & EFs. I'm not expecting much by simply cleaning the valve. Replacing it is only about $40, so I may go that route next.

http://www.justanswer.com/honda/2hhr...las-vegas.html

#2 in the following pic:

 

Thanks for this. It's getting hotter in South Texas and I remember having this issue last year. I'll check that.

 

Cleaning the 2-way valve has not changed anything on the EG.

My next option is to swap in a larger OBD1 charcoal canister. EX EG's & some Del Sol B16's came with the same larger ToyoRoki brand canister found in all 94-95 Integras. My 94 CX came with the smaller Tennex brand canister, and I have a feeling it might just be getting overwhelmed. Who knows. I have a used Toyoroki on the way right now.

Should be here in a day or two, and I'll report back once I try it out. If it works on the EG, perhaps there is a way to adapt one of these canisters to the EF.

Toyoroki canister 1.3 lbs


Tennex canister 1.0 lbs

 

Got both canisters out and measured them for reference....

Tennex: 533 grams
Toyoroki: 628 grams

I'm really hoping this helps. When I run the AC, this car gets pretty stinky at the stoplight. I'll report back tomorrow.

 

It doesn't really sound like the heat has anything to do with it.
To me, it seems that your EVAP is just not working right and the heat just makes it more apparent.
Putting a larger canister on it just seems like it is going to catch more vapor and you will still have the issue of the vapor not being released properly.

Try completely replacing the 2 way valve rather than just cleaning it.

 

That will definitely be my next step if this doesn't help. I need to order a bunch of parts anyways. Thanks for the insight.

The sucky part is the EF 2-way valves are discontinued. If the CRX starts getting as bad as my EG, I'll have to get creative.

 

delete the damn canister... u aint in cali

 

He seems to be in Nevada where they do SMOG checks that include a visual check.

 

These are registered classic-rod and classic-vehicle which means no inspections if you drive less than 5k miles a year each.

So if you delete the canister how do you vent excess fuel tank pressure and/or the allow fuel drop to draw air into the tank? At least without stinking up your garage with gas fumes. Please explain.

 

Okay beefier canister didn't help. Smells exactly the same. Glad I only wasted $15.

I'm pretty sure it's the 2-way valve then. I'm guessing it's not opening soon enough, thereby causing too much pressure inside the gas tank. Then when the valve finally blows open, so much vapor comes out all at once, it overwhelms the charcoal canister with fumes before the throttle-body can consume them via the purge hose.

I disconnected the evap hose from the throttle body, and there really is very very little draw from the motor (on both cars). When you pop it off there is no audible hiss (over the normal motor noise) and no change in idle from an open vacuum source. I guess this system is supposed to draw from the charcoal canister quite slowly.

I'm wondering if years of me topping off the fuel tanks (they say don't do that) has finally caused me problems with these two-way valves.

 

Just to update.....My findings after talking with the Honda shop foreman are that this can be quite normal in the summer. It's the very reason the government mandated sealed EVAP systems in 1998. The system simply gets overwhelmed in high heat of summer and cannot flow enough of the fumes into the throttlebody to keep them from escaping via the fresh air vent.

We'll see how bad it is again as it gets hot out here.

***EDIT: Changed 1996 to 1998. That's when Honda added the "Vent shut" solenoid to the charcoal canister to control the flow of fresh air and prevent fumes escaping. 1996 was the year Honda changed the canisters (in North America) to use direct manifold vacuum to purge the canister (instead of the weak passive draw from the throttle body nipple found on 1995 and earlier). The 96-97 canister still had an open/unregulated fresh air port.