Odd gas leak - need input...
Thread Starter
Instructor
Joined: Oct 2007
Posts: 196
Likes: 0
From: Vero Beach Florida
Odd gas leak - need input...
Odd things always seem to happen to my cars.
The latest - I've smelled fuel around my '81 the past few days. I've not driven it until I could check it out. Smell seemed to be coming from the master cylinder area??
Well, I was close - The bottom of the VACUUM RESERVIOR is wet with raw fuel and dripping on the steering linkages!!!
I'm thinking I over-filled on my last fill up (which was about the time I started smelling gas).
Thoughts anybody? We're not driving the car until I get to the bottom of this!
Thanks!!! ...Alan
The latest - I've smelled fuel around my '81 the past few days. I've not driven it until I could check it out. Smell seemed to be coming from the master cylinder area??
Well, I was close - The bottom of the VACUUM RESERVIOR is wet with raw fuel and dripping on the steering linkages!!!
I'm thinking I over-filled on my last fill up (which was about the time I started smelling gas).
Thoughts anybody? We're not driving the car until I get to the bottom of this!
Thanks!!! ...Alan
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Sounds as if the fuel evap container is probably full, which would happen if you just overfilled the fuel tank. The system is working as designed, I would take the car for a nice run and that will empty the evap container.
Racer
Joined: Dec 2002
Posts: 319
Likes: 3
From: santa clara ca
no fuel regulator on mechanical pump from factory unless installed after. i would have to agree with "dannyman" Charcoal cannister. Now is the leak coming from the brakes vacuum power assist reservoir the only the fuel is there can only be way of vacuum line is it t'd to the cannister.
Drifting
Joined: Oct 2007
Posts: 1,458
Likes: 1
From: Collinsville MS
St. Jude Donor '08
I agree with Dannyman, check the lines on the fuel evaporation canister under the master cylinder, its against the inner fender and see if any of your lines have dry rotted and started leaking.
Thread Starter
Instructor
Joined: Oct 2007
Posts: 196
Likes: 0
From: Vero Beach Florida
Thanks for the replies.
Vacuum lines are not wet with fuel, they're dry and a bit spongy so I think I'll change those out.
The only area wet with fuel is the bottom of the charcoal canister. The wife filled up the car - removed the nozzle when it clicked off - so, I don't think the tank was "overfilled".
Is fuel getting continuously sucked into the canister or was the canister filled up after we filled the tank and it's gonna take awhile to drain?
And, taking it out for a long drive with the raw gas inches from plug wires doesn't sound real safe!
ARRRRRGGGG!!! We were going on a long drive up the coast tomorrow!
...Alan K.
Vacuum lines are not wet with fuel, they're dry and a bit spongy so I think I'll change those out.
The only area wet with fuel is the bottom of the charcoal canister. The wife filled up the car - removed the nozzle when it clicked off - so, I don't think the tank was "overfilled".
Is fuel getting continuously sucked into the canister or was the canister filled up after we filled the tank and it's gonna take awhile to drain?
And, taking it out for a long drive with the raw gas inches from plug wires doesn't sound real safe!
ARRRRRGGGG!!! We were going on a long drive up the coast tomorrow!
...Alan K.
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Cruising
Joined: Jan 2008
Posts: 10
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If the car has been filled up and it was cold outside than parked in a warm garage and the car was sitting the least bit down hill as the themperature in the garage warmed up the expansion of the fuel in the tank will force liquid fuel into the charcoal canister in the front of the car. Thus the fuel smell. Open the garage door, vent the fumes out, start the car, drive for about 10 miles. It will run like crap for a while untill the canister is completly vented then it will run like it should.
Thread Starter
Instructor
Joined: Oct 2007
Posts: 196
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From: Vero Beach Florida
markcaro, Thanks for the input.
After STILL smelling fuel this morning, I wiped the area down and took the 'Vette for a half hour run this afternoon - armed with my trusty fire extingusher. Sure enough, the car ran rather poorly at first but smoothed out after a few miles. Smell has subsided and there's no new fuel dripping from the cannister - yet. I'll see what it looks like in the morning.
How/why does fuel get pulled back to the cannister? Bad gas cap?? Outside temp wasn't a factor this week in Florida - days were in the 70's, nights high 60's (bummer, eh?
)
I think I'll just put $30 each fill-up rather than the normal $45!
...Alan K.
After STILL smelling fuel this morning, I wiped the area down and took the 'Vette for a half hour run this afternoon - armed with my trusty fire extingusher. Sure enough, the car ran rather poorly at first but smoothed out after a few miles. Smell has subsided and there's no new fuel dripping from the cannister - yet. I'll see what it looks like in the morning.
How/why does fuel get pulled back to the cannister? Bad gas cap?? Outside temp wasn't a factor this week in Florida - days were in the 70's, nights high 60's (bummer, eh?
)I think I'll just put $30 each fill-up rather than the normal $45!
...Alan K.
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
There is a check valve at the tank end of the evaporative system that should keep fuel from running down into the evaporative canister. Maybe your check valve has given up the ghost and it's time for a new one. You might have to drop the tank to replace the valve - I don't know offhand if you can access it with the tank in place.
Rick B.
Rick B.
Cruising
Joined: Jan 2008
Posts: 10
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In cooler weather, even though you live in florida oil companies reformulate the vaporization characteristics of the fuel as to lower the temperature that fuel will vaporize in cooler weather for better performance in cooler temperatures and raise the vapor pressure in hot weather to keep fuel from boiling and creating drivability issues and possible vapor lock in a carburated engine application. Therefore a 15 to 20 degree temperature change and you filling up the car possibly overfilling it even little bit will create enough of a pressure build up in the fuel tank to force liquid fuel into the vapor canister, saturating it and overflowing with fuel. The filler neck on a corvette is all the way on top of the tank and it is easy to over fill it. Stick the fuel nozzle into the fill as far as it will go and when it clicks off the first time don't put any more fuel in it. There is also the possibily that the fill nozzle on the gas pump is defective and it's fuel cut off is not working properly causing an overfilled tank. This might be an isolated situation and shouldn't happen again. If it happens again more investigation into the problem is warrented Hope this helps you, Mark
Thread Starter
Instructor
Joined: Oct 2007
Posts: 196
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From: Vero Beach Florida
Looks like this leak may indeed temerature related. Our temps here in Vero Beach have been between 68 and 87 degrees for the last week - no leaking from the cannister. Yesterday, we took a 100 mile road trip to see daughter and grandson. Car ran great!! This morning a front had gone through and outside temp was down to a chilly 56 degrees and there was a dinner plate sized gas stain on the drive from the cannister.
I wiped everything down and went for a 10 mile drive this morning. Parked the car 3 hours ago - no leak (yet).
Needless to say I can't let this continue to happen.
I looked at the vacuum lines leading to the cannister. One was a bit spongy and probabaly needs to be replaced. The gas cap is an aftermarket. Pulled the rubber back at the filler area and the lines look and feel good.
Please, guys - any ideas? I've had one car fire in my life ('68 Bug) - I sure don't want another.
to see daughter and grandson. Car ran great!! This morning a front had gone through and outside temp was down to a chilly 56 degrees and there was a dinner plate sized gas stain on the drive from the cannister.I wiped everything down and went for a 10 mile drive this morning. Parked the car 3 hours ago - no leak (yet).
Needless to say I can't let this continue to happen.
I looked at the vacuum lines leading to the cannister. One was a bit spongy and probabaly needs to be replaced. The gas cap is an aftermarket. Pulled the rubber back at the filler area and the lines look and feel good.
Please, guys - any ideas? I've had one car fire in my life ('68 Bug) - I sure don't want another.
Safety Car
Joined: Sep 1999
Posts: 4,930
Likes: 11
From: AnyTown NJ
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I'm not sure about an 81 but if you have a charcoal canister it's probably setup similar to my 71. This canister has several hoses connected to it. One hose is connected to the vacuum port on the front of the carburetor. Another hose is connected to the PCV valve on the left front valve cover. Another hose is connected to the fuel vapor return line which runs alongside the drivers side frame rail and connects to the vapor separator on the upper left side of the fuel tank. The charcoal canister is there absorb gasoline vapors only, not raw gas. The usual cause for raw gas to find it's way to the canister (over filled gas tank on a hot day) is a defective fuel separator valve. This valve attached to the gas tank allows vapor to flow to the charcoal canister but prevents gas.
You might want to check and see if you have such a valve....and replace it.
You might want to check and see if you have such a valve....and replace it.
Safety Car
Joined: Sep 1999
Posts: 4,930
Likes: 11
From: AnyTown NJ
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Not on a 71, but as I said I'm not famular with how an 81 is setup. I would check the AIM and or the Service Manual for your year.
