gas smell when coasting
Thread Starter
Instructor
Joined: Aug 2006
Posts: 151
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gas smell when coasting
72 350 nom. when im going down a hill and take my foot off the gas pedal, i get the smell of gas if the window is down or the tops are off. as soon as i push the pedal, the smell is gone. does this problem ring a bell with anyone. thanks..Don
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The 1969 -1976 Corvettes without air conditioning came equipped with Astro Ventilation. This ventilation system included two doors in the rear of the car that opened up when you put the heater control select switch in the “Air” selection position. When this was done, the kick vents opened as well as the rear vents allowing air to flow through the **** pit of the car. The vents are controlled by vacuum pods both in the front and the rear.
With this in mind and just as a suggestion you might check two things.
1) A leaking gas tank. A real easy way to see if you have one and don’t know it is to look at the exhaust pipes. Gas, when dripping on the pipes will turn dark brown. If you are leaking fuel then this would explain the odor.
2) An Astro vent door opening due to the rise in vacuum when you let off the gas pedal. You may have a vacuum hose that is not correct which could cause this or some other issue. But if you are leaking fuel and the doors are opening then I would guess this to be the issue.
To smell fuel inside the car it has to be leaking somewhere from the tank.
Willcox Inc
With this in mind and just as a suggestion you might check two things.
1) A leaking gas tank. A real easy way to see if you have one and don’t know it is to look at the exhaust pipes. Gas, when dripping on the pipes will turn dark brown. If you are leaking fuel then this would explain the odor.
2) An Astro vent door opening due to the rise in vacuum when you let off the gas pedal. You may have a vacuum hose that is not correct which could cause this or some other issue. But if you are leaking fuel and the doors are opening then I would guess this to be the issue.
To smell fuel inside the car it has to be leaking somewhere from the tank.
Willcox Inc
Last edited by Willcox Corvette; May 24, 2007 at 08:48 PM.
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Look at the bottom of your tank where the sending unit is attached. If you see stains it's leaking. If it is it may just be the rubber ring gasket is shot and is easily relpaced. I replaced the gasket first but still leaked, then had to replace my sending unit because there was a hairline crack where the metal tube attaches to the plate. No more gas smell or leak now.
Glenn
Glenn
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
If you dont find a leak in your tank here is another thought.With the high engine vacuun on coast I wonder if the canister is trying to purge.If the charcoal is wore out or not there and the canister recieves a blast of fumes from the tank it will come out in the engine compartment.Just a thought! You could remove the hoses coming from the engine and block them and go out and try it.
Thread Starter
Instructor
Joined: Aug 2006
Posts: 151
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thanks for all the guidance guys. with the long weekend ill have time to check them all. another uneducated thought, could it be the carb? when i have to make a quick stop it sometimes wants to die out. and have been getting a up and down idle as well. and the car is an automatic. the tips are much appreciated. don
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Verdad Gallardo
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Look at the bottom of your tank where the sending unit is attached. If you see stains it's leaking. If it is it may just be the rubber ring gasket is shot and is easily relpaced. I replaced the gasket first but still leaked, then had to replace my sending unit because there was a hairline crack where the metal tube attaches to the plate. No more gas smell or leak now.
Glenn
Glenn
BTDT, but I being a cheeep bastard, took some hard plumber's solder and some cleanup and acid, and used a torch super carefully to fix mine....so far so good....time will tell....
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
thanks for all the guidance guys. with the long weekend ill have time to check them all. another uneducated thought, could it be the carb? when i have to make a quick stop it sometimes wants to die out. and have been getting a up and down idle as well. and the car is an automatic. the tips are much appreciated. don
OK, over the years, decades even, living in the Maryland/Mid Atlantic region, I found the heat riser was a super PIA in the summer, and was therefore fond of taking plaster of paris and blocking the manifold heat rise passage tighter a drum....let it harden overnight...and then reinstall....of course this means you have to have an electric choke, not some vacuum operated 1/4 inch air loop type thingy or some manifold heated spring on a landing type Mopar thing.....
The heat releif enables the carb to rum MUCHO cooler, and boil off less gas when hot....
course a good cooling system also helps....you got bad cooling, it just makes everything else worse....
Racer
Joined: Dec 2003
Posts: 275
Likes: 6
From: NY
I have a '71 that stank of gas until it got under 3/4 full. There is a plastic tank attached to the gas tank on the driver side. It is part of the BS gas fume recycliking system. On mine the POS tank's lower half departed this life. I fixed the problem.
