1967 Mustang gas tank over flow when filling.

[huptoy]

When filling my 1967 Mustang, the gas explodes out the tank at the 3/4 mark.  Still happens when filled very very slow.  The Mustang doesn’t use a vented tank.

 

Previous owner passed away before finishing a major restoration including motor & trans rebuild, new interior, repaint including most chrome parts. 
 

The tank was already installed when I purchased it.  Is it possible the gas tank is partially blocked or am I missing the problem.  A new tank is easy to replace not really expensive.

Edited February 14, 2021 by huptoy (see edit history)

[TerryB]

Air is trapped somewhere.  When I was a gas pump jockey in the late 1960s it was a comm occurrence for many cars to do this.  On some you could actually hear it getting ready to blow back at you.  Not sure if there is a cure for it.

[John Byrd]

Wow, that is a curious thing. The Mustangs from that era couldn't have a simpler path for the gas to flow, and as the tank is flat on top, it should just keep filling until it runs back up the curved filler. Now if it was a Falcon wagon or Ranchero, they are real slow to fill. Let us know what you find out huptoy. Only thing I could imagine might be possible is if the gas is going in WAY too fast.  

[critterpainter]

Is the 3/4 of a tank what the fuel gauge indicates?  If the gauge is a china replacement it might be more inaccurate than the original gauge.

[huptoy]

Good thought on the China gauge but it will take another 3 to 5 gallons after it over flows but very slowly.  It has done this since first got running.  I have filled it from 3 gallon cans without any problem.

[TerryB]

1956 Chevy with the filler inside the left rear tail light always blew back.  I hated those cars when they pulled up to the pump.  I really expected to see one burn up some day while I was filling it.  Lots of those center rear fill up cars were good for that too and the ones with the fill behind the license plate were just as bad.

[avgwarhawk]

https://www.vintage-mustang.com/threads/67-68-mustang-vented-filler-neck-write-up-no-more-spills.625035/

[kgreen]

I have a 67 and experience similar issues.  The solution I have is to turn the fuel filler nozzle sideways and fuel slow.  I often get a burp at the end that fills the flip down fuel cap, then runs down my bumper.  When I fill, I keep a mental note on the amount of fuel that should nearly fill the tank and listen for the rising pitch from the fuel flow, then quit.  Kinda sucks but with a 10-gallon tank, the long fuel fills are mostly from talking to people about the car.

[Graham Man]

Same problem on my 72 Mustang and 65 Falcon.  I just attributed it to the short distance between the filler and the top of the tank.  My favorite part is when you are trying to listen to the tank fill up.... and some kid is telling you how cool your car is....  I just grab a paper towel to wipe off the bumper when I start to fill it.  I don't think my original Mach 1 spilled?  Maybe I was too young back then to care if it spilled, and gas was cheaper.

[54vicky]

on my 54 owned since 76 early years no problem.as time went on and gas went up in price I  am sure the pump makers increased the volume it pumped.now when I hear that gurgle I ease up.

[kgreen]

17 hours ago, 54vicky said:

on my 54 owned since 76 early years no problem.as time went on and gas went up in price I  am sure the pump makers increased the volume it pumped.now when I hear that gurgle I ease up.

They changed the size of the fuel discharge nozzle to fit the smaller hole in the new car fuel filler.  That was when they wanted to make sure you didn't pump leaded gas into a catalytic converter equipped car.  The nozzle senses back pressure but in the older cars with the larger opening in the fill neck, the pressure is not recognized so the cut off doesn't work as effectively.

[c49er]

Certain Ramblers and if course Mustangs were cars I hated putting gas into when I was a kid working at the gas station.

Slow and blow back.

Awful . 

  

[huptoy]

The fix appears to work!  Setup a pipe bypass between the top of gas tank & the filler pipe.  I just put in 14 1/2 gallons & it shut off at full, didn’t splash or spill a drop.

[Pete O]

Excellent!  I'm surprised Ford didn't have a vent already built into the filler pipe.  Could it be that your filler pipe is a repro that lacks the vent that an original would have?   I recently obtained a '57 T-Bird, and had the same issue.  I got soaked the first time I went to fill it up.  There is a small diameter vent pipe soldered to the outside of the filler pipe and it ducks into the pipe about four inches from the neck- above where the tip of the gas pump nozzle would sit when filling up.  The other end attaches with a rubber hose to a fitting on the fuel level sender to allow the tank to vent.  The vent pipe had filled up with crud so that the tank could not vent when being filled.  I replaced the whole filler neck with a repro and problem solved. 

[trini]

That is a common sense fix. Sense is not so common with some engineers

[Mark Gregush]

On 2/18/2021 at 3:08 AM, kgreen said:

I have a 67 and experience similar issues.  The solution I have is to turn the fuel filler nozzle sideways and fuel slow.  I often get a burp at the end that fills the flip down fuel cap, then runs down my bumper.  When I fill, I keep a mental note on the amount of fuel that should nearly fill the tank and listen for the rising pitch from the fuel flow, then quit.  Kinda sucks but with a 10-gallon tank, the long fuel fills are mostly from talking to people about the car.

My 1975 Maverick was the same way. I think it has to do with that sharp bend so close to the opening, and the modern vapor recovery hoses at the gas station.