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MG MGB Technical - Gas fumes in boot?

Hello all!

I have a problem with gas fumes in the trunk (boot) of my '72B. It is the vented tank, and is new. There are two hoses that go to the vapor separator that seem to be causing much of the odor, and are in need of replacement. Of course they are no longer available through Moss, and are special hoses that thread into the tank and through the floor. All emmission equipment is gone off the car in the engine compartment, except for the adsorption cannister, and a few hoses that connect it to the carbs. Any advice on how to remedy this problem is much appreciated.

Thanks,

Shawn
Shawn Herndon

I replaced my cracked vapor canister hoses with regular low pressure fuel line from a local auto parts store. The boot on my 80 B still reeks like gas. I just don't put anything back there.
Brian

I have a simmilar problem, I've got a 1977 B and the trunk (I know, I know, British car=Boot!!!) smells like gas all the time, oh well, I can live with it.
K McCaffrey

The line could also be blocked enroute to the carbon canister ahead of the firewall. You might want to blow it out.

There also could be a rot spot in the rubber sleeve that connects the filler to the tank. No doubt you've checked the two clamps there for snugness.
Dan

Shawn. You need to evaluate the entire system. First, my 79 has a piece of steel line, with a nut, attached to the gas tank. The hoses are standard 1/4" fuel hose. Thus, it should be possible for you to set up a similar system if the factory style hoses are not available. Most of the cars I have seen over the years are running fuel hose rather than the factory style braid covered hose. Hose clamps will hold everything tight.

Dan is correct that if the large rubber union is bad, gas fumes can escape. Check it and see if there is obvious damage. All of mine have been replaced over the years because of cracking. If you believe you still have an original union, replacement is easy and inexpensive. Dan is not, however, correct that the line forward could be blocked. When this happens, the fuel pump creates a vacuum in the gas tank because it is not vented. You will hear a "whoosh" sound when the car has been run and the gas cap is opened. On my daughter's 77, with a Faucet pump, the situation was so bad, the gas tank was damaged. PO's mechanic (DPO'sM?) had removed the line to the vapor seperator to allow the system to vent properly. I reconnected it and found the problem of the plugged line.

Have you dropped your gas tank? They tend to rust on top first (I am told--not a big problem in Arizona). If the top of the tank is rusty, you would get a smell of gas from the trunk area.

Vapor seperation tank and all of the hard and soft lines need to be checked out. Replace as necessary.

Check out the fuel pump and its connections to make sure there are no leaks. If there are, vapors can collect in the trunk area. (The rest are blown away, but the trunk will collect them and are noticable in even small amounts.)

If you have a smell of gasoline in the trunk, you have a leak somewhere and need to find it before it becomes dangerous. This is not a "feature" of the MGB. Neither of my current RB cars have this and my original 79 did not have it. Check out all of the system, including dropping the tank and inspecting for holes, removing the vapor seperator and inspecting for leaks, etc. Gas burns, vapors explode. Les
Les Bengtson

Shawn. Have responded to your off line e-mail, but will do a follow up to get some of the information into the archives.

The vent fitting on the tank seems to be 1/4" pipe thread. I was able to attach that sized fitting to a spare gas tank I have in the shop (off a 77). A good hardware store or plumbing supply shop should be able to provide the fitting necessary to build a system that would incorporate replaceable rubber fuel line as the connections. Use teflon tape or teflon paste on the connectors at the gas tank and the right front of the trunk/boot. On my 79, there is a large nut-type connection at the right front of the boot and it is attached to a metal line which then runs back near the vapor seperator and terminates in a bare hard line. Fuel hose, secured with the proper clamps, attach to the end of the line and to the vapor seperator. None of the vapor seperators I have installer or in my spare parts have threaded connections. Rather the can has two metal tubes coming out of it over which the rubber hoses are fitted and clamped. It sounds like your system may have been modified over the years if the vapor seperator has threaded connections attached to it. You should be able to make up connectors, with a short length of hardline attached, to fit to the fuel tank and floor of the trunk, then connect them to the vapor seperator using fuel line and clamps. Les
Les Bengtson

All the later model RB "B's" that I have seen have the rubber hose and not the threaded steel braided lines going to the vapor cannister. Are all these change overs from the original set-up or was this a factory change?
Frank

And then on those 30 year old rubbers, I've found invisible cracking at the clamp. Grab everything and jerk it around. Just had this wonder on the 1980: Before I replaced the pump to tank hose break, I wiggled the old hose around and it crumbled in my dirty little hands.Good, I wouldn't have it any other way. Vic
vem myers

Shawn:

I had the gas smell problem on my 78 and it turned out to be that the sending unit seal wasn't all the way tight. It was loose just enough to let fumes out but not leak.

Joe
Joseph Maggiore

While we're here, does it matter how the separator is hooked up? Is there a directional flow? On my 77 both connections (top & bottom) face toward the back. Should the bottom connection go to the tank and the top to the canister? does it matter?
Dan H.
D.E. Hanson

Hi
I used to have the wonderful scent of gas in the car and found out that the fuel pump connections were not as tight as they could have been . A little tightening and all is well . Haven't smelled gas since. Nothing worse than the smell of gas while driving.
Alan

Dan,
Top to canister and bottom drains to tank, otherwise you'll be sucking petrol.
I also had a smelly boot and it turned out that the tank vent, located under the filler neck, had a small crack along one side.
Fixing this plus replaceing all the hoses took care of the problem. I used ordinary fuel line.
Now I can hold my head high and declare"My boot has that ring of confidence"
Peter

Knucklehead here!

Vapor canister? Is that the round thing attached to the side wall in the little "pocket" to the right outside the boot in a GT? Spotted that on my new purchase, a '71, and didn't remember having one on my '74 that I drove from '75 to '80. Couldn't find it in any of the drawings in Moss or Brit Vic. If that's it, thanks for the ID! Is it part of the North Am. smog stuff or standard on all? And is there any maintenance?

John "Knucklehead" Randolph
J. L. Randolph

John; The vapor/emissions cannister is in the engine compartment on the right rear for US cars. What you are describing is the vapor separator, item 76 on page 79 of the current Moss catalog. One should have been in your 74 if it was a US car. My 74 has one and I removed one from a 71 parts GT. It is as you mentioned part of the NA smog gear. FWIW, Clifton
Clifton Gordon

This thread was discussed between 26/09/2003 and 10/10/2003

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