View Full Version : TR2/3/3A Gas Smell

07-16-2013, 09:59 AM
I have a smell of fuel in the garage from my resently restored TR3A (1000 miles on restoration). Everything in the powertrain/fuel system is new from the tank to the carbs. I've checked everywhere for any sign of gas leakage without success. I've pulled the tank out (new tank) and checked both the drain and fuel line ports. No gas is coming from the rebuilt carbs or the fuel line connectors. It does have a Moss aftermarket fuel pump (with primer lever) that came with a input fuel line adapter built in to match the fuel line threading. I've tightened and sealed all the connections. The only idea I keep coming up with is the new Moss fuel cap, but have no reason to think it isn't sealing fine. I am 'losing' fuel if it sits for a long time but nothing showing leakage anywhere. I had thought that it was losing more fuel when the tank was full but can't swear to it. It's a mystery. I've been rebuilding Triumphs, MGs and other cars for years and this is the first time with this problem. Any ideas? Pat

07-16-2013, 10:24 AM
Here's the same answer I gave over at the TR experience...

"The gas is evaporating into the air, causing the drop in fuel level and the smell of gas. I have the same problem. And yes, the problem is more pervasive when the tank is full. What I've done is plug the vent line (without any fuel delivery issues), and that stems some of the loss, but I think that the gas cap is also a big offender. Mine is also new from Moss. Perhaps the original cap was vented less then the Moss unit."

07-16-2013, 10:38 AM
Thanks. I've already put a small piece of shrink tubing at the end of the vent pipe, now I'm going to try putting a thin sheet cut from a sandwich bag under the cap and see what happens. I'll let you know. Pat

07-16-2013, 10:41 AM
Perhaps the original cap was vented less then the Moss unit."
We've had some discussions on that topic. Apparently some of the original caps weren't vented at all, but all of mine have had a roughly 1/16" hole

https://i258.photobucket.com/albums/hh260/TR3driver/TS13571L/th_Gastankventholeincap.jpg (https://s258.photobucket.com/user/TR3driver/media/TS13571L/Gastankventholeincap.jpg.html)

Since gasoline evaporates so readily, a small leak may not leave enough to drip and still leak enough to smell in a confined space. Try running your fingers along the bottom of the carbs, especially the bolts that hold the float bowls and the clevis for the mixture jets. If you can smell fuel on your fingers, something is weeping.

Doesn't sound like your problem, but I'll throw it out anyway. Twice now, I've had a leak at the tank filler pipe (once Stag, once TR3) that was very hard to find. On the Stag, apparently there was a small pocket of fuel that would get caught between the filler tube and the tank neck while filling the tank, and then slowly leak out over time. On the TR3, the original filler tube was some kind of rubber that would soften and leak when it got wet with modern fuel; then harden up again once the level got low enough to never splash up on the filler. I might never have found it, except the tank shifted and stretched the tube until something was obviously wrong.

07-16-2013, 10:51 AM
Thanks for the note. I've been all over everything numerous times, and pulled the gas tank twice. Nothing. Given the loss of gas, I struggle to think this is all evaporation, but short of anything else that's where I'm heading. I'm just now finishing up my latest TR3A project and it has all the same parts (new) that this car has. Hope I don't get deja vu all over again! Pat

Tony P
07-16-2013, 07:09 PM
What I experienced after installing a new Fuel tank is that most of these tanks are generic enough to fit multiple models of cars. After installing my new tank I came out into the garage and was startled to smell the strong odor of gas fumes. After searching the entire fuel system I was laying under the car when I noticed the gas fumes coming out of the vent pipe. I lay there for 10 minutes just watching the fumes drifting out. I then installed a short fuel hose and plugged it with a short piece of pencil. I left it for the next morning and then I checked it there was no fuel smell. This led me to believe that if I pinched the vent pipe enough to cut the vapors from coming out but leaving enough space for overflow it would work. And it did, I have no more fuel smell and it was a simple fix.

Tony P

07-16-2013, 07:33 PM
When you say you replaced everything...I don't trust the new replacement olive fittings they sell now days. Mine had a small leak at the fuel pump outlet. The more I tightened the olive, the more it leaked. It did not leak when I looked, as the engine was not running...so no pressure in the line. But, those olives are used in at least a couple different fuel joints.

I finally gave up and used sealant along with the olive. Works great now!

07-16-2013, 08:10 PM
This led me to believe that if I pinched the vent pipe enough to cut the vapors from coming out but leaving enough space for overflow it would work.
FWIW I've had that tube blocked completely for many years with no problem. Otherwise, with a nearly full tank of gas, it will dump liquid fuel on the ground every time you turn left.

Back when "full service" was the standard for gas stations, I also once had a pump jockey keep trying to fill the tank into the neck. When i came back from the restroom, he was standing in a spreading pool of fuel, still trying to get the last ounce in the tank.

Geo Hahn
07-16-2013, 08:12 PM
I usually use a brown or blue paper towel (like they have at gas stations) to feel for any leaks around the carb or fuel pump. As Randall notes, gas can evaporate before you get a good look at it and even a small amount can make a rather pervasive smell. The darker paper towels are better for showing even the slightest bit of seepage. Probably best to check right after a drive.

07-17-2013, 07:25 AM
As I passed through the garage this morning I did NOT have the strong smell of gas! (I had put the sheet of thin plastic bag under the cap). Although I did drink a number of beers last night and it could be clouding my senses. Short of that, maybe I've located the gas loss/smell problem. I'll check again this afternoon. Hopefully, this is it and I'll go looking for a o-ring/gasket for the cap. Pat

07-17-2013, 12:50 PM
Wait a second. In each of the 4 British sports cars I have owned, that smell of gas was a requirement. If I didn't end each drive with my hands covered in grease and smelling like an oil tanker, no one would know that I was the one who drove up in the sports car. It is a chick magnet I tells you. Now, without that smell, people will just assume you drove up in the Camry (not a chick magnet). Just my $0.02.

07-17-2013, 10:03 PM
Does the gas smell go away after a few hours? On our TR4A, after months of checking all fittings, etc., I determined there was a bad carburetor float. While driving gas would saturate part of the air cleaner. When parked in the garage the smell was terrible. After a few hours it would evaporate eliminating the smell. Just a thought.

07-18-2013, 08:23 AM
I never noticed the smell after driving, just when it sat in a closed space there would be a smell of gas. And, if it sat there a long time gas would disappear. When I drove for long distances I would measure the gas usage and noted that my mileage was OK (24 mpg). As noted above, I checked everything many times and just lately decided to put the plastic bag between the cap and the cap fitting. The smell in the garage is GONE. I would never have thought that I could lose 'gallons' of gas through evaporation, but I'm assuming the problem is now solved. Thanks for the note. Pat

08-07-2013, 10:46 AM
Thanks for opening this thread. I have had the same strong smell of gasoline and was a bit worried every time I hit the garage door opener. I followed the advice given here and tried to source a replacement seal for the fuel lid - to replace that reddish, rock hard original rubber one. No luck.
The answer was to make one out of a scrap piece of leather. It just sits in there seals nicely.
To plug the vent tube I used one of those red plastic plugs made to plug the end of open calking tubes.
I used a tap to thread the inside of the vent tube and a die to cut threads on the plastic plug. A little thread seal and it spun in like it belonged there.
It's neat fix that can easily be undone.
I can now open the garage door without ducking for cover.