Having trouble filling gas tank full

[19stang66]

So ever since I got my car last year, I have been having trouble filling the tank full. I put the pump on automatic like I would with any other car, but once it starts to shut off automatically it shoots gas back out all over my bumper and valance. It's not even close to being full when it shuts off. So then I start filling it manually, with barely any pressure on the lever so I can control the flow.
I can watch the filler neck fill with gas, so I stop the flow. Then the gas is sucked into the tank, it makes that gulping/swollowing sound. It's like there isn't air getting into the tank when I fill it, causing it to overflow.

So my question is, how do I fix this overflowing problem? Also when I do think it's all the way full I turn the car on and the gauge only reads 3/4 full. The guage never goes all the way full. So I filled up at 1/4 tank tonight and I only put in 6 gallons because it was doing that overfilling thing and I though it was full, but again the gauge said it wasnt. Whats the problem here?

 

[19stang66]

I am also smelling gas fumes in the trunk area all the time. The rubber filler neck connector looks new so I can't see how that would be the problem. There arent gas leaks anywhere that I know of. Any other ideas?

 

[68stang351]

You're not alone, my 68 does the exact same thing. I even have to fill it up the same, with barely any pressure on the lever. Not really sure why though, or how to fix it.
Must be a common problem.

 

[mustangman1974]

Its the new vapor gas nozzles. my 68 has a sweet spot where I can fill her up on full. If your smelling gas checkl to see if the coupling is attached correctly. I should have clamps you can tighten. IT they are loose thats where the gass smell is. Or you little rubber hose on the bottom of the gas tank is bad.

 

[68keyblr]

Yeah, whoever invents the gadget that allows you to get a clean fill up on a classic mustang will be my hero!

It's always a pain in the butt to fill up both the '67 and '68...I've found that certain pumps at certain stations do a better job than others, and I always go to the pumps that I know work better.

I just put a new fuel gauge sending unit in my tank and it maxes out at just below 3/4 tank too. I'm going to pull it out and bend the lever down a little, hopefully that will make it go to full when the tank is full.

 

[Cannoball888]

I have this problem too, but it has to do with the price of gas.

 

[Tim65GT]

I have this problem too, but it has to do with the price of gas.

You're in the wrong hobby...

 

[goom49]

The problem is that new tanks have a high spot that vents back to the nozzle area thus allowing fuel in and air out. Try to force the fuel to run along the lower wall of the filler tube so the air can escape through the top and try to park facing down hill a little.

I have seen some magazine or company use a tube and some fitting to vent the tank to the top of the filler neck. I look around for a picture.

But I have planned to adapt a late model filler neck to my '67 for years to make this process easier and less messy. Maybe this summer I will get around to it.

 

[thehueypilot]

The problem is that new tanks have a high spot that vents back to the nozzle area thus allowing fuel in and air out. Try to force the fuel to run along the lower wall of the filler tube so the air can escape through the top and try to park facing down hill a little.

I have seen some magazine or company use a tube and some fitting to vent the tank to the top of the filler neck. I look around for a picture.

But I have planned to adapt a late model filler neck to my '67 for years to make this process easier and less messy. Maybe this summer I will get around to it.

I have the same issue and I noticed a 87 - 93 Mustangs have a filler neck that might fit into the 68's. I thought about cutting the flapper neck and installing it into the inside of the filler tube.

 

[19stang66]

Well now i know im not the only one with this problem. Thanks for the tips!

 

[1320stang]

Yeah, it's pretty common. In Oklahoma, we still have the old looking nozzles with the spring around it. Wehn I bought my '65 in '87, I could fill it up, and it would stay on 3/4 tank for a long time. I bought a new sending unit and changed it out. Found one of those nozzle springs wrapped around the float.

I know of some guys that would take the neck loose and spin it 180 and have it sticking up in the trunk. This eliminates the slow fill and keeps people from siphoning your gas, but since the gas cap is vented, the fumes spill out into your trunk, and therefore, into your car. You could weld a tube to the neck and run a piece of fuel line up, then down thru the floor of the trunk which would solve that problem.

 

[bnickel]

i've found that when the car is sitting level or slightly lower in the back i've had this problem as well. right now that back sits about 1.5" higher in the rear and i don't have the problem. i would fashion a vent tube to run from the tank to the top of the filler neck to correct the issue. an old school trick my dad taught me is to rock the car side to side as you're filling the tank and that helps free the trapped air in the tank

 

[Sodaholic]

hmm.. yeah i wanna get like a tube like 1/4 or 3/8 and pop a hole in the top of the tank and then run the tube along side the filler neck. maybe if i somehow had a metal tube that ran inside the filler neck with the opening at the top of the tank and had it flatten out as it got close to the top of the filler neck so that it would not obstruct the nozle going into the neck. i dunno.. maybe if i knew how to bend pipe without ruining it i would.. haha. so maybe ill just so the first one.

 

[1320stang]

If I were to make up some vented necks using a Stainless Steel vent tube, would anyone be interested? What you be willing to pay? I'd have it as an option that you could send your neck in as a core and get a used neck back or I could use a new repop neck. FYI, a new neck is $15-$20. This would be primarily for '65-'68 Mustangs as I'm not aware that it's a problem with the '69-'73, but it could be done for those easily enough. I'd also need to know if you have the correct year tank for your car and if it's a repop tank or not.

 

[68conv4sp]

same problem with my '68. There are a couple of gas stations in our area where the concrete pad at the pump slopes downward. So I stop with the front end pointed downhill and the car fills without the back splash. As for the guage, it never reads above 3/4 full, despite the NOS sending unit.

 

[CochinoFilipino]

If I were to make up some vented necks using a Stainless Steel vent tube, would anyone be interested?

I would definitey be interested.

 

[1320stang]

I would definitey be interested.

So what would you be willing to pay? What sounds fair? I don't want to make anyone feel like they're getting screwed on the deal, but I also don't want to do it for free. The tubing is like 3/8" and it would be bent inside of the fill neck and bend into the top of the tank, you wouldn't notice it on the outside and it would be welded to the neck. I'll have to do some test fitting to make sure it won't interfer, but it shouldn't. I'll also need to know what the diameter of the nozzles are in your area as I know California has that vapor recovery boot on the outside, but I don't know if the nozzle that goes inside looks different or not.

 

[CochinoFilipino]

So what would you be willing to pay? What sounds fair? I don't want to make anyone feel like they're getting screwed on the deal, but I also don't want to do it for free.

I wouldn't want you do it for free either. I think $15-20 to modify is fair. At that price it's still more like your doing a favor, as you're not going to make much money that way.

Where'd you find 15-20 for a new neck? An old NPD catalog I have has them listed at 40 and 48 for repros.

 

[goom49]

As for the guage, it never reads above 3/4 full, despite the NOS sending unit.

Everyone is talking about the gauge never reading above 3/4, but I have never had that problem. When I bought mine in '95 the gauge would go past full and back around to 1/4 when the tank was completely full. so I got a new tank and sending unit and it has worked great since then. As long as I filled it up slow it would actual fill full. I usually ended up having a little gas poor out of the filler tube. I would first check the sending unit, it should show between 0 and 12 volts when full or empty (forget which order). Otherwise maybe the gauge or wiring is going bad.

 

[1320stang]

I was thinking about $20 for the modification myself.

The $15-$20 filler necks are ones I've seen on Ebay.

With this modification, you shouldn't have to fill slow. I may also offer them with a new rubber connector if the owner feels he needs one.

I figure the way I'd do it was once I had the bends figured out, I'd build a jig to bend them right and that would make it easier. The tubing I'll be using is pretty heavy wall, it's high pressure tubing they use in the oil field, so if the bottom end that hangs out of the neck needs a little tweeking, it shouldn't be a problem. The rubber should cover up the weld at the bottom, it's the one up top I don't want to show. I want this modification to be able to be put on a concours car if desired and not be detectible.