to check the lines from the tank to the frame i looked under there without a lift and felt around after i ran it for just a minute.

checkall those lines and the fuel pump like others said. another thing to check is the vapor canister. i think it can cause a gas smell but that doesnt explain the dripping while driving

 

OK, home at lunch today, no gas smell in oil/dipstick. No stains anywhere, slight smell of fuel on passenger side under fender behind rear tire... will check lines more closely tonight. Thanks all!

Bill

 

As others have stated check your fuel line from tank to pump on pass side.....you should not smell any gas unless there is a leak.

I would also check the evaporative emissions control setup. This consisted of a black plastic charcoal canister that is located in the driver's side engine compartment, roughly in the space between the back of the wheel well and the firewall. The 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. This separator is made of plastic and over time fails which can allow gas to travel to the charcoal canister especially if you over fill the tank....don't ask me how I know.

Lastly I would invest in a good fire extinguisher for your car and garage as well as getting the Assembly Instruction Manual and the Service Manual for 71.

BTW, for 70 to 72 fuel systems were sealed not vented......not sure about other years.

 

If you over fill the tank & top it off, fuel will drip down the overflow line or tank if it's not there anymore. That's probably what they saw dripping. Since you can see how much gas is in the tank you'll know when it's full. This happened to me so now I fill it untill about 1 1/2 - 2 inches from the top of the tank.

 

Bill,
If you lay down under the left rear of the car and using a flashlight, look up above the muffler, at the top front of the tank you should see one of these, 70-74 TANK VAPOR SEPARATOR.

These things are notorious for leaking over time and will produce all of the symptoms you've mentioned if they do leak. You can replace it without dropping the tank or muffler, although both will make it a lot easier. It has two rubber hoses that connect to it. One very short one goes to the tank and one longer one goes to a hard line on the left side frame rail which travels up to the front where it connects to the charcoal cannister.

I have found it easiest to remove by disconnecting the hoses from the tank and hard line and removing the hoses after you get the vapor separator out from under the car. There are two small screws that attach it to a bracket on the top of the tank. If you know what you're looking for, you can remove it by feel pretty easily. Cut two new pieces of hose to fit, attach them to the separator and then reinstall the assembly in the car.

These have only recently become available new and in the past, we had to search for an old one that wasn't leaking. They would sell for as much as $75 at Carlisle. They can sometimes be resealed, but trust me it isn't worth it if you can get a new one for this price...
http://www.zip-products.com/Zip/prod...F2FF45220C9C23

Good luck... GUSTO

I apologize Bill, you said the passenger side... this is on the left (driver's) side. As other's have said, I would check the rubber lines that go from the tank to the hard lines on the right side frame rail. The large one is the feed line and the smaller is the return line to the tank, if your car has the return line.

 

OK... I think we're getting close here. Didn't drive her today so no gas use. No odor at all under the hood, in dipstick, up front at all. Slight odor driver side rear near exhaust. Much stronger on passenger side behind rear tire. Felt tubing along body, no obvious moisture, but couldn't really tell what I was touching. Wish I had a lift!!! Noticed a "clean" area around the circular "fitting" under the gas tank - see photo, 6:00 to 9:00 area. It's not a shadow. Not really wet to touch, but looks like it has been wet as it doesn't have the dust I see everywhere else. Whaddayathink? Does this look like a potential leak to you guys? If so, what's the fix? Remember... I have limited skills but I'm willing to learn. I'm also willing to admit when I'm in over my head and find a pro...

You guys are the best... thanks for all the help! Come to Rock Hill and I'll but you all a beer!

Bill

 

I had exactly the same trouble with my 71 LS5. It was worse on a full tank as the fuel would slosh and escape through a crack in the vapor separator. Had the car for almost a year before I figured this out. I too had it chalked up to the "all the old cars smell like gas" thinking. Now the only time I smell fuel is when I pull the air cleaner.

Keep looking, you'll find a leak somewhere...........

 

Bill,

One weak link in the system is the rubber seal that goes between the bottow of the tank opning and the strainer base.

There is a slight concave feature on the tanh that O ring rides in.

Also the sending unit's tube is soldered to the base plate.

The base plate can also become porus over the years and allow a small amount of weepage. I think that's a word.


1st. for safety get car outside , I would also drive it and use up some gas.

2nd. disconnest battery


3rd. Get a clean 5 gal. bucket.


4th. jack up back of car and secyre with stands


This willalso allow some gas to run to front of tan and won't have to be drained.


Remove the fuel line with 1 hand while ready with the loose piece of 3/8 hose in other hand.

Then slide the loose piece over the nipple and allow to drain into bucket.

Have some vice grips ready if bucket does not hold all , you can crimp off line until you switch to a 2nd. bucket.

once fuel finishes draining set the buckets far away from car.

Up plug the wires.

There may be a tool to remove the twist lock , but I used a hammer and a flat blade screw driver to tap the cam around to the release point.

You will replace the rubber O ring and may find it nessacary to replace the sending unit.

In any case order a in tank strainer and replase while you are there.


David


Not too hare to replace. Get piece of 3/8 hose about 2' long.

Then

 

I did the tank changeout project this time last year. My tank had a crack and the left muffler was stained from gas dripping on it from above. That was enough right there to make me do the job. I dropped the tank, cleaned up the entire rear area and replaced the tank and lots of other miscellaneous stuff while there. I did not replace the vapor separator. I did replace line and clean it up and use new clamps. No more leak on the mufflers.......... I think the whole project ran about $250.

First thing to do if you are going to change out the tank is to drop the exhaust. Makes life a lot easier.

 

Anti squeak strips held moisture in my 69, tank rotted through on both sides.....................B

 

Looks like a good candidate to me, I believe you found it

 

My issues went away after I switched gas caps.

Obviously check for leaks and correct those first.

 

Believe them

Recently had a similar problem.
It did not drip at idle, but under way when the fuel pump was pumping a little more it leaked and over time got worse.

Here is a pic of the leak when it became noticeable. You can see the smoke as it hits the hot muffler.


Here is the evidence of stains on bottom of the muffler.


Here is the return line with a hole in it. It was inside the last hold down clamp on the top of the frame beside the tank just before the rubber line.


If you can smell fresh gas you have a problem. These cars didn't stink of gas new and shouldn't now.

 

Had the same thing on our '78 L48 pace car. Feedback from folks on the forum and personal digging led me to changing gas cap (bought new from GM), vapor canister (bought new from GM), all rubber lines connected to the vacuum canister, and the 'S' hoses at the fuel pump. All of the hoses were cracked quite significantly.

Fuel smell be gone!

I'd get it fixed.

Take care and have a Happy Thanksgiving

GaryC - Franklin, IN..

 

Looks like the sending unit is leaking. I believe you can get a new o-ring for that. Check the tank too though. My 69 leaked directly above the front and rear supports. Just enough to get the anti-squeek pads wet and stink up the garage. Not enough to leave a spot on the floor.

 

Thanks for all of your input guys... I really appreciate it. Noticed some odor at the gas cap, and plan to replace that as well. Seems like this has been a common problem, with a wide variety of causes. Am going to try to get the car on a lift in the next week or two and see if I can find any further evidence of leakage. If not, will replace that seal and the cap, and see how it goes.

Saw another thread on this forum where someone finagled a new carb out of a gas cap replacement... hmmm... wonder what else I can blame the smell on??? I think that old radio may be the problem honey... LOL.

Thanks again y'all!

 

Actually, 70+71 were SEALED systems, at least if you had the L-46 optioned motor. The non-califorinia L-46 has no cannister, either. Very strange. I had a big-time problem with my sealed cap, and have since gone to a vented cap. In fact, most of the time, I run with the gas cap gasket removed. Interested why? Read here.

 

I haven't read ever post but after re reading your OP and a few others I think your going to find your leak in the return line on the top of your tank.The fuel that shows in your pic is probably coming from a leak at the top-if it was from the o-ring gasket it would leak as long as there was fuel in the tank and the undercoat on the tank would stay wet.Remove the rubber from around the gas cap and look back to the right with a "flashlight" and I'll bet you'll see your leak.
edit-If you want to go one step further and you feel safe doing it you can start the engine and run it at 1500 until the return starts to flow good and watch the rubber connector.

 

Just had this problem with my '72 when I filled it to put it away for winter. I am almost positive that it is leaking through the gasket between the tank and filler neck. Yes, the tank was very full and it stopped as soon as I siphoned a small amount of gas out. I had also noticed the gas smell other times after filling the car and having gas sloshing around in the tank just not as bad. I am sure it's just an old dried out gasket.
Happy Thanksgiving.
Eric