A new look at my problem!!!!
Thread Starter
Racer
Joined: May 2011
Posts: 373
Likes: 6
From: Dover Delaware
A new look at my problem!!!!
Alrighty then C3'ers,
Got the 78 AIM page 385 in front of me and am trying to find out where the heck does the fuel vapor tube/line end at the end from the tank to my non existent vapor canister???
I would like to trace the routing to its end and see exactly where it is venting to the atmosphere but cannot seem to be able find anything running along the frame..Perhaps it is running thorough the frame and exits where??
Why...because I have fuel odors in my garage and looking for a way to eliminate them without having to do the canister reinstallation....
Fuel tank and sending unit have been replaced the car runs great with no evident fuel flow issues....
Any and all feedback, as usual, would be greatly appreciated..
mk's78
Mike
Got the 78 AIM page 385 in front of me and am trying to find out where the heck does the fuel vapor tube/line end at the end from the tank to my non existent vapor canister???
I would like to trace the routing to its end and see exactly where it is venting to the atmosphere but cannot seem to be able find anything running along the frame..Perhaps it is running thorough the frame and exits where??
Why...because I have fuel odors in my garage and looking for a way to eliminate them without having to do the canister reinstallation....
Fuel tank and sending unit have been replaced the car runs great with no evident fuel flow issues....
Any and all feedback, as usual, would be greatly appreciated..
mk's78
Mike
7th Gear
Joined: Feb 2008
Posts: 7
Likes: 0
Got a 78 L-82, pulled out the canister about 6 months ago. Painted it, replaced the filters, refilled with fresh charcoal, and replaced all the tubes. The tube at the bottom of the canister vents to the atmosphere inside the frame itself. The tube is about a foot long and routs into a small hole in the frame just behind the driver's front tire. There are no special connectors.
I had fuel odors too, I'm honestly not sure the canister was my biggest problem. Most of the vent line is steel but the rubber tubes connecting to both ends of the steel were split open from years of exposure to gas. Check these and if you replace, make sure you get tubing rated for gasoline; they last much longer! My local parts store (A-Line in Tx) sold this grade of tubing in various diameters for about a buck a foot. McMasters is also a great source if you can wait on shipping!
I had fuel odors too, I'm honestly not sure the canister was my biggest problem. Most of the vent line is steel but the rubber tubes connecting to both ends of the steel were split open from years of exposure to gas. Check these and if you replace, make sure you get tubing rated for gasoline; they last much longer! My local parts store (A-Line in Tx) sold this grade of tubing in various diameters for about a buck a foot. McMasters is also a great source if you can wait on shipping!
Last edited by kels83; Oct 31, 2019 at 09:48 AM.
Race Director
Joined: Mar 2016
Posts: 14,402
Likes: 8,209
From: Napa Valley California
When I bought my 73 I had fuel odors in the garage and spent hours trying to locate the problem.
I replaced the lines, rebuilt the canister and still had fumes.
I took it to a local Corvette specialty shop and they replaced the fuel separator, which is a plastic device on the top, drivers side of the tank, where the vent line connects to.
No more fumes.
They told me this is where most people fail to check and is usually the cause.
I replaced the lines, rebuilt the canister and still had fumes.
I took it to a local Corvette specialty shop and they replaced the fuel separator, which is a plastic device on the top, drivers side of the tank, where the vent line connects to.
No more fumes.
They told me this is where most people fail to check and is usually the cause.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
When I bought my 73 I had fuel odors in the garage and spent hours trying to locate the problem.
I replaced the lines, rebuilt the canister and still had fumes.
I took it to a local Corvette specialty shop and they replaced the fuel separator, which is a plastic device on the top, drivers side of the tank, where the vent line connects to.
No more fumes.
They told me this is where most people fail to check and is usually the cause.
I replaced the lines, rebuilt the canister and still had fumes.
I took it to a local Corvette specialty shop and they replaced the fuel separator, which is a plastic device on the top, drivers side of the tank, where the vent line connects to.
No more fumes.
They told me this is where most people fail to check and is usually the cause.
and for years, no one made them, so you were stuck with what you could find used at a swap meet or junk yard. I recall a guy at Carlisle having a bucket of old used vapor separator valves selling for $75 each. No good way to test it without adding gas to it, so it was like buying a pig-in-a-poke. A while back someone started making them so reproductions are available today at a reasonable price.FUEL SEPARATOR VALVE Price: $50.00
Paragon Number: 12439
GM Part Number: 7028035
Years: 1970 - 1974
https://www.paragoncorvette.com/p-35...tor-valve.aspx
Good luck... GUSTO
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If there is a drain tube from the bottom of the vapor canister, it should NOT be routed into the frame of the car. In the instance that raw fuel is dumped into the vapor canister, the fuel is meant to be dumped to the ground. This condition should not occur; but it is possible with a full fuel tank, a defective fuel seperator valve, and a really bumpy road.
My suspicion is that there is something wrong with the vapor canister. Either your rebuild of that device altered its designed behavior or the activated carbon that you exchanged from it is not doing the job. If only fuel vapors are reaching that canister, the carbon material could hold it until the canister (when car is in operation) is signaled to release it into the intake charge. If the canister is not getting the signal to release the vapors, the carbon will eventually get saturated and just spill the excess....normally to the ground; but in your case, into the frame of your car.
My suspicion is that there is something wrong with the vapor canister. Either your rebuild of that device altered its designed behavior or the activated carbon that you exchanged from it is not doing the job. If only fuel vapors are reaching that canister, the carbon material could hold it until the canister (when car is in operation) is signaled to release it into the intake charge. If the canister is not getting the signal to release the vapors, the carbon will eventually get saturated and just spill the excess....normally to the ground; but in your case, into the frame of your car.
Thread Starter
Racer
Joined: May 2011
Posts: 373
Likes: 6
From: Dover Delaware
Well folks ya know ya just never know what goes along with C3 ownership..
I even amazed myself yesterday....I finally found the vent line from the fuel tank that it routed along the D/S frame and it ends about 10 inches from where the OE vapor canister was removed by the PO and it was uncapped and was venting to the atmosphere!!!
I installed a rubber line from the end of the steel line and installed it in the PCV line to the carb with a home spun T fitting..
I am hoping that this fixes to fuel odor smell in my garage..
Again, any and all comments are sincerely welcome...Or better said..Do you folks think it will work and solve my problem??
mk's78
Mike
I even amazed myself yesterday....I finally found the vent line from the fuel tank that it routed along the D/S frame and it ends about 10 inches from where the OE vapor canister was removed by the PO and it was uncapped and was venting to the atmosphere!!!
I installed a rubber line from the end of the steel line and installed it in the PCV line to the carb with a home spun T fitting..
I am hoping that this fixes to fuel odor smell in my garage..
Again, any and all comments are sincerely welcome...Or better said..Do you folks think it will work and solve my problem??
mk's78
Mike
Race Director
Joined: Mar 2016
Posts: 14,402
Likes: 8,209
From: Napa Valley California
So basically you are just bypassing the charcoal canister.
Hmmmmmm.
Will that pull constant vacuum through the vent line from the fuel tank?
What is the possibility of pulling fuel into the carb if the tank is overfilled or fuel is sloshing around with a full tank?
I'm sure someone will chim in with technical comments.
Hmmmmmm.
Will that pull constant vacuum through the vent line from the fuel tank?
What is the possibility of pulling fuel into the carb if the tank is overfilled or fuel is sloshing around with a full tank?
I'm sure someone will chim in with technical comments.
Last edited by OldCarBum; Nov 1, 2019 at 02:21 PM.
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Verdad Gallardo
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You really don't want to plumb it in that way. By design, that vapor line goes to the vapor canister; the 'output' of the vapor canister goes to the PCV "T"....BUT, the canister does not PURGE into that T unless a vacuum signal from a 'timed' carb port is received. The reason for this is that you do NOT want the canister to purge while at idle or the excess vapors/air will screw with your idle quality. It only purges into the carb base when the car is in "cruise" mode (partial throttle).
With that vapor line going to the 'T" 'full-time', it will mess the idle quality up. Now, if you are fine with how it idles with it plumbed that way, so be it. I just wanted you to know WHY it was not designed that way.
With that vapor line going to the 'T" 'full-time', it will mess the idle quality up. Now, if you are fine with how it idles with it plumbed that way, so be it. I just wanted you to know WHY it was not designed that way.
Last edited by 7T1vette; Nov 2, 2019 at 07:19 PM.