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Cannot fill fuel tank

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crgrbrts Avatar
crgrbrts Gold Member Craig Roberts
Wheaton, MD, USA   USA
1970 MG MGB MkII "Bumblebee"
I know this topic has been addressed before, but an answer seems to elude us. Here goes:

After driving 120 miles, a refueling effort was thwarted by the fact the tank would take no more than a gallon an a half of fuel before spewing from the filler neck. This happened no matter how I positioned the pump nozzle or how little fuel pressure I allowed. I got similar results with a gas can and long nozzle. Also, after the car has been sitting for a while, removal the gas cap results in considerable spillage of fuel. It's as if only the filler neck is being filled with very little fuel getting past it.

Despite this, the car runs normally -- though I won't get very far on a gallon a a half of petrol at a time.

What's happening??

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course2kid Jeffrey Johnson
Fountain Valley, CA, USA   USA
1979 MG MGB "Lucy (Lucifer)"
I don't want to insult your intelligence, but, I have to ask - are you sure the tank isn't actually full? Maybe the fuel sender or fuel gage is broken and reading lower than the actual level.

It seems to me that if you can get a gallon to go in, then the filler neck isn't blocked, so what could make it take some fuel but only a limited amount? The fill neck can't hold a gallon of gas, so some must be going into the actual tank.

edit: Sorry, just reread your post and noted that you drove 120 miles, so, surely, it should have accepted more than 1 to 1-1/2 gallons.

Maybe this post has the answer to your particular problem:,2961476

Edited 2 time(s). Last edit at 2017-05-16 10:36 AM by course2kid.

dipstick Avatar
dipstick Kenny Snyder
La Center, Washington, USA   USA
1941 Ford N-Series
1958 MG MGA 1500 Coupe "Rosie"
1970 MG MGB GT "Pat's GT"
1971 MG MGB "Gifted To Me"    & more
Could the bottom of the fuel tank be crushed upwards?

Be safe out there.

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Gerry Avatar
Gerry Gold Member Gerry Masterman
Prairieville, Louisiana, USA   USA
I believe it's time to open your trunk and remove the fuel fill line and look inside the tank. Knew someone who had some ass pour a bunch of popcorn in his tank, not a MG though, and it caused him all kinds of misery. You have any enemies?

crgrbrts Avatar
crgrbrts Gold Member Craig Roberts
Wheaton, MD, USA   USA
1970 MG MGB MkII "Bumblebee"
No offense taken, Jeffrey.

The tank is definitely not full, unless I am getting a phenomenal 119 miles-per-gallon (if so, I'll figure out how and share my secret -- for a price). I had driven 120 miles when I attempted to re-fuel. Normally, the car will need 5 - 6 gallons at that point. It took between 1 and 1-1/2 gallons and will now take none after driving another 30 miles.

There is some fuel in the tank as evidenced by a light "sloshing" when I bounce the car's rear end.

The tank looks intact and perfectly normal in dimensions. I would postulate that an interior bladder had collapsed, but these things don't contain bladders, do they?

Rufus Avatar
Rufus Gold Member Harry Singleton
Garland, Texas, USA   USA
1967 MG MGB
1967 MG MGB GT Special "Rusty"
1974 MG MGB GT "Krusty"
What Gerry said,,,

Have fun

If ignorance is bliss, I must be the happiest man alive!

67 Roadster

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crgrbrts Avatar
crgrbrts Gold Member Craig Roberts
Wheaton, MD, USA   USA
1970 MG MGB MkII "Bumblebee"
I am a retired Capitol Hill reporter. I have many enemies - but most of them wouldn't bother with a popcorn-in-the-gas-tank prank. They would just have me snuffed. KABOOM!

late 64 Terry O
Milton, Ont, Canada   CAN
might be easy enough to remove the filler neck from the hose inside the trunk and have a look see whats up...?? as you say does not make sense since this a big opening.........confused smiley

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Chalky Avatar
Chalky David White
Coventry, Warwickshire, UK   GBR
Modern fuel pumps are designed to fast fill the tank so you move on quickly and they can sell fuel to someone else. The design of the filler neck on the B causes some splash back in the neck that triggers the pump to think the tank is full. Change the angle of the pump nosel and fill it slower.

Defender405 Avatar
Defender405 Silver Member Chris B.
Des Moines, Iowa, USA   USA
1975 MG MGB
I would suspect an issue with the filler hose. The system is pretty stupid simple, just a rubber hose that goes from the filler neck down into the tank. It should be pretty easy to disassemble and look over. I don't recall that there was anything significant in the tank that would break loose and cause problems either. Maybe check the breather line, though these are really nothing like a modern car where the breather is usually the issue.

Chris AKA "Defender405"
1975 MGB
1979 Porsche 924
1999 Porsche 996
1987 Nissan 300ZX

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course2kid Jeffrey Johnson
Fountain Valley, CA, USA   USA
1979 MG MGB "Lucy (Lucifer)"
Craig, after my first dumb answer, I felt I owed you a little bit better response... I took off my gas cap, used a screw driver to hold the unleaded nozzle flap open and snaked a bent coat hanger into the tank. As soon as it got past the filler hose to tank junction, it went all the way to the bottom of the tank as evidenced by the sound of it hitting bottom. You might try that as a quick and easy check of your filler hose.

Since you can't even fill from a gas can with a long neck, it isn't related to the gas station pump kicking off due to splash back. Maybe the filler hose has collapsed internally. It's a big hose, so, it seems unlikely, but, when you've ruled out all the probable causes, you have to start looking at the improbable ones.l!

Edited 1 time(s). Last edit at 2017-05-16 03:07 PM by course2kid.

jmart1419 Avatar
jmart1419 Silver Member Jim Martin
Vancouver, Washington, USA   USA
What David said. If the nozzle has a spring shut off requiring you to push it all the way in it will shut off too early. Hold the spring back and do not put the nozzle all the way in. Be careful and fill slowly because the last little bit is just filling the filler hose.

geezer Avatar
geezer Silver Member charles durning
Magee, Mississippi, USA   USA
1958 MG Magnette ZB "Chick Magnette (sold)"
1967 Morris Minor 1000 Saloon (2-door) "Marvin"
1974 MG MGB GT
I vote for the fill hose causing the issue.

Who's version of right are we talking about? When you get 10 LBC owners in a room you'll get 12 different answers.

Edited 1 time(s). Last edit at 2017-05-16 03:03 PM by geezer.

ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, Alberta, Canada   CAN
1971 MG MGB
On all cars with the evaporative loss system (which I believe was introduced in 1970) there is a canister inside the tank that is meant to maintain an air bubble during filling. It is basically a can with an opening on the bottom that traps air. This prevents the tank from overfilling, Basically, the tank appears to be full, then when you drive a few blocks the trapped air bubble jossles free and you find you are down half a gallon or so.

But you are experiencing the opposite - and the most the canister can ever displace is about a gallon or maybe a little more.

I agree with the other guys - pull the tube off in the trunk and look down the hole with a non-flammable light (a spark would be a Really Bad Thing! - perhaps a small LED penlight would be best). There must be something blocking the entry. Is it possible the canister has come loose and floated over to cover the hole? Seems like a long shot.

Terry Ingoldsby

crgrbrts Avatar
crgrbrts Gold Member Craig Roberts
Wheaton, MD, USA   USA
1970 MG MGB MkII "Bumblebee"
Thanks, Terry. I'll make an "in depth" inspection as soon as I get home tonight. I was planning to drop a match down the filler neck and gauge the actual fuel quantity in the tank by the severity of the ensuing explosion, but perhaps I'll employ your LED penlight method instead.

A curious thing is the spontaneous appearance of this phenomenon. I've been refueling routinely without incident for a year. I think it's a gremlin. -- the same one one that causes my fuel gauge to read "full" even when the tank is half empty. (I have replaced both the sending unit and the gauge without solving that annoying little problem, by the way).

Edited 1 time(s). Last edit at 2017-05-16 04:51 PM by crgrbrts.

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