Leaking fuel line - Gas tank pressure?

[HSSS427]

Went out for a drive and after about 45 minutes I got a strong whiff of gasoline coming into the car. Pulled over, and sure enough there was gas running off the rear of the frame all over the ground. Couldn't get under the car to get a good look at the line, but figured I either cracked the -10 AN aluminum tubing, or the AN fitting where the tubing converts to braided line was loose.

Was going to have it towed home since I have road side coverage, but then the insurance company said I had to call the fire department first to secure the car before they'd dispatch a tow truck.

So, when the firemen arrive, they started watching the underside of the car and said they hadn't seen it dripping. So we moved it to the side, jacked up the rear, and I removed the left rear wheel so I could get at the fitting and line. (note to self - remember to keep the lead knock-off hammer in the car, and but a jack).

We decided to start the car to see if we could tell where the leak was, but when I did - no leak. Let it run for a while and still no leak, so I decided to drive it home.

When I got home and got it up on the lift, everything looked dry. Tried tightening the fittings a bit, and looked over the line, but am a bit befuddled by it all.

My only guess at this point is - could the gas tank have gotten over pressurized and caused fuel to leak out of the line at one of the connections? What is the typical set-up for venting the gas tank as I assume it's not supposed to build up pressure, right? Any other ideas?

Thanks!
Scott

[strictlypersonl]

The LeMans fuel cap has a vent built in, but you should check it anyway. Are you using a rear-mounted electric pump?

[HSSS427]

Using a high volume, mechanical pump. Have Lemans cap with a lockable cap underneath.

[Wayne Maybury]

How full was the tank? The gasket on my gas gauge sending unit was leaking at one point but only when I was driving the car with a full tank of gas. However, it would not leak if the car was sitting still even with the tank quite full.

Wayne

[HSSS427]

Checked the venting and realized it wasn't venting at all.

The filler neck was originally installed to use the standard LeMans cap with no other cap underneath. When I took it to the track, I had to put a cap on the tank under the LeMans cap, so bought one of those locking caps at the local store. However, the vent line underneath that hadn't been connected.

I thought it was, but then found it was a drain line from the indendented area around the fuel cap to allow overflow to drain off. So, have installed a 3/8" fuel line from the vent outlet on the filler neck to underneath the car. Also tightened up the connections and such as well. Hopefully that will do it. Track day tomorrow at Road Atlanta - yee haw!
Thanks!

[DonC]

I also had a bad gasket on my fuel gauge sending unit that would only leak when the tank was full or nearly so or moderately full under high acceleration and cornering loads. Just something to check if everything else looks tight.
DonC

[Jerry Clayton]

If you have a fuel system with even the slightest question about its proper operation, stay off the race track---that is no place for a high octane fuel leak

Jerry