imgon HalfDork
5/21/19 2:20 p.m.

Due to the engine running so rich I have ruined another vapor canister.  Mazda PN N326-13-970. These are NLA and I'm unable to get a cross reference number to some other model that may use something similar. How close does this need to be to my existing unit? It has two nipples on top, ~ 1/8" and 1/4" for lines to the fuel system and one out the bottom for  a drain. While it would be great to find one that is plug n play I just want something that will be effective in containing fuel vapors.  What are my options?

imgon HalfDork
5/21/19 2:21 p.m.

dculberson UltimaDork
5/21/19 2:37 p.m.

Is it clogged or just not effectively containing the vapors? The vapor is supposed to be pulled back out and burned by the engine. If it's clogged, you can try unclogging it like this:

alfadriver MegaDork
5/21/19 2:47 p.m.

Yea, can you explain why you think running rich makes the cannister fail?  Unless the system is so broken that it's never being purged....

Streetwiseguy MegaDork
5/21/19 6:21 p.m.

What do you mean by ruined?  Full of gasoline?  Charcoal falling out? 

imgon HalfDork
5/21/19 7:14 p.m.

It stinks badly and seems to be a block of charcoal instead of a filter. I had this problem back in 2014 and was building up pressure in the gas tank. I noticed at my race a few weekends ago that when I undid the gas cap it hissed a little. I'm thinking that I just need something to filter the vapors and as long as I have the appropriate size nipples for the hoses I am good. Size of the canister shouldn't really matter as long as it vents? Thinking about it, I wonder if something is clogged in the line that goes back to the intake.  Is that something that has a vacuum and should have a check valve? 

Knurled. MegaDork
5/21/19 7:57 p.m.

The engine has absolutely nothing to do with the vapor canister's state of health.  It is merely a kind of reservoir to retain vapor from the fuel tank when the engine is shut off, and then when the engine is running, it pulls the gasoline vapors out and burns them.


Evaporative emissions is a huge thing.  A vehicle with no evap system pollutes more just sitting there with its engine off than a 10 year old car did driving down the highway (when it was new at least)


It seems to be a block of charcoal because it IS a block of charcoal.  It isn't a filter, it is a reservoir for fuel vapor and it uses activated charcoal to store the vapors.   And the gas tank hissing when you remove the cap means that the evap system is working, it's retaining the fuel vapors and keeping them from being released to the environment (or at least, it does when the fuel cap is off).  That is why there are/were/used to be warning labels that the fuel tank may be under pressure!

imgon HalfDork
5/22/19 7:20 a.m.

In reply to Knurled. :

Thanks for the explanation, I will leave it in place. While installing the new components for the fuel system it smelled horrible under the hood and I narrowed it down to around the area of the canister. I found a bunch of goo under it and believed it to be from the canister. But it smelled more like mouse pee, so I am now thinking I have a mouse that built a condo somewhere in the car and will have to go find it. Thanks again.

aw614 Reader
5/22/19 11:25 a.m.

Are there any purge valves or solenoids that may need to be repalced?

imgon HalfDork
5/22/19 11:32 a.m.

In reply to aw614 :

Does not seem to have any purge capabilities, just a plastic case with three hoses.

Knurled. MegaDork
5/22/19 11:45 a.m.

In reply to imgon :

It's old school for sure.  One of the three hoses is to ported vacuum, to open the valve any time the throttle is open past idle.  (Purging at idle can cause weird issues on a non-feedback controlled engine).  IIRC one end goes to the canister and the other goes to the crankcase, with Mazda running the vapors through the crankcase before it gets to the engine.  (Been a while since I tinkered with stock vacuum routing, I may have this wrong)

iceracer UltimaDork
5/22/19 6:32 p.m.

Vapor canisters are normally mounted in the rear well close to the tank.

Knurled. MegaDork
5/22/19 6:48 p.m.
iceracer said:

Vapor canisters are normally mounted in the rear well close to the tank.

Not on RX-7s.  SAs put it inside the air cleaner, FBs had it on the passenger fenderwell, and I forgot where FCs had it.


GMs also has the canister underhood for the longest time, too.

TurnerX19 HalfDork
5/22/19 11:18 p.m.

Lots of cars have had front mounted vapor canisters, MG, Volvo, Mazda, some Jaguar. Really it can go anywheres and still work, and they are all functionally similar.

iceracer UltimaDork
5/23/19 2:06 p.m.

OK, I guess I haven't been around many cars in a few years.

Hungary Bill
Hungary Bill PowerDork
5/23/19 2:31 p.m.

What perfect timing for this thread! 

After a gas cap change on my Toyota 4-Runner, the tank pressurized and filled the charcoal canister with gas.  I've fixed the issue, but did I kill my canister?

Also:  My gas cap is vented to avoid pressurization (like what happened with the charcoal canister), doesnt that negate the purpose of the charcoal canister?

Thanks guys.


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