How to route a fuel vapor canister
 

My vette had all emission control apparatus removed from the engine. I was trying to get to the leaking windshield washer fluid jar and since I was going to from under the car, I removed the fuel vapor canister - I figured I should work on another problem as well which is fuel odors in the car.

The fuel line to the the canister was the only one connected. The rubber hose hose was in bad shape and once I started moving the canister it broke apart. That may have been the source of the fuel odor but cannot be sure. On this canister the port marked "to carb bowl" is plugged using some silicon. There is also a line in the bottom of the canister that is plugged with silicone.

My intention is to route this in some fashion to essentially eliminate any fuel odors escaping in the engine department and avoid having the wife bitching that the Vette smells like gas. The car does not have an EGR valve.

Any thoughts are welcome.

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What year car are you working on ?

Sorry, the car is a 1979, L82, original motor but stripped of emissions with Edelbrock intake and carburetor

Get a Vapor Can off a late model 3/4 ton or 1 ton Truck, I goes from the tank to the canister ,one from the canister to the Carb, Three openings, one Vent makes the third. I for got what year truck I took mine off of. I think 1995 it is a little taller than the original, V.C. It works fine on my 454 powered El-Camino. Don't forget to buy a new filter for the V, C. they sell them at all auto stores, Gene

I am thinking since the motivation is to burn fuel fumes I could go to an earlier version of the canister where there is a connection from the tank and the a connection to the PCV system and be done with it - instead of dealing with five ports, cut it down to two... thinking of using this canister: http://www.mamotorworks.com/Corvette...ister-622003-1

That's what I did on my '80, I will go out today and take some pics of the way I hooked mine up.

I am going back ten years off my memory but you still need to connect the canister to the to the gas line on that side of the car, after all that's what stinks and that is one of the purposes of the vacuum canister.

When I did this my garage didn't stink anymore, worked perfect. :thumbs:

I think I am going to settle on this - the dimensions match - all I have to do a tee it into the PCV line going to the carb and that should pretty much take care of the fumes.

Looking forward to this, thanks!

There are three (3) primary connections for any vapor recovery canister:

1. line from fuel tank to send vapors to canister;
2. "purge" line going from canister to PCV valve outlet/carb base inlet;
3. signal line from carb (timed/ported vacuum) to 'tell' the canister when to purge vapors. [DO NOT connect manifold vacuum to the cansister.]

In the late '70s, the emissions systems got more complicated and added other lines to the canister. You should search Google for the vapor recovery canister connection diagram so that all associated vacuum lines are properly connected.

Hi L,
As part of the vapor control system there needs to be a 'separator' of some type to ensure that only vapors and no gas travels forward through the line running to the canister.
On earlier tanks it was mounted on the side of the gas tank...might be on top of the tank on your 79?
Regards,
Alan

Early separator.
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Hmmm..... I will have to check - I have the fuel sending unit out at the moment so it may be easy to check ... do those go bad?

Hi L,
The separator is pretty simple so they really don't 'go bad'.
Sometimes the type I pictured can leak because of a crack.
I'm really not sure how the one on your tank might be configured.
Regards,
Alan

Here is the canister 71-72 that uses just 3 lines..
One from the tank
One from the canister to the carburetor.
One from the canister to a T at the pcv valve and then to the base of the carburetor.
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The 2 hoses running from the canister mounted on the rear side of the apron to the carburetor.
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They must have stopped using a separator at some point, there's none on my '77. Unless it's internal to the tank.

your 77 vette has it ,its now built in with the filler(neck) area on the access lid up on top of the tank , the only thing that really wears out or degrades with age is usually the rubber lines coming off it to the main steel line that runs along the frame rails .

to the original poster , many years ago my 77 had just the line from the tank connected to canister and I didn't have fuel fume problem . But my bottom outlet wasn't blocked up either , sounds like someone drowned yours in petrol and didn't fix the problem

This is AWESOME! Thanks Alan!

As part of the fuel level sender assembly, there is contraption that might actually be considered a fuel vapor separator? There is a hollow bulb inside that rises presumably to cut off the fuel going to the canister. As the fuel drops, then the vapors travel to the canister..

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I had the same problem with my 72. I removed the canister and plugged the plastic valve at the tank that Allen mentioned and installed a vented gas cap and the smell went away. You will always have a very small amount of gas smell which is normal for a carbureted car.

Hi,

"You will always have a very small amount of gas smell which is normal for a carbureted car."

Sorry, but I disagree with "always" and "normal".
Regards,
Alan

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When I had to solve the mystery how to reconnect the old canister that had been capped and forgotten long ago, I found that the '77 has only two lines on top, one from the tank, and one to the carb.

I have a Quickfuel carb and not the original Quadrajet so I just tee'd the carb line into the PCV. But as you can see in this photo, I have two modifications. The big arrow shows the cheap vacuum valve I used to prevent the PCV from drawing the fuel vapor at idle. I don't have a lot of vacuum at idle and didn't want to risk having even less. The valve has a line going to a timed vacuum port on the carb. So it is closed at idle, and open at operating speed.

The other mod is a law mower fuel filter that I'm using in the line coming up out of the canister because the old charcoal filter is emitting some fine black dust and I don't want that in my intake. I now have no fumes in the garage, and I do not release fuel vapor into the atmosphere through a vented cap.

Steve


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Awesome job and good idea on the filter. I think I have all the parts to put mine together