Gas Tank Options For A MII

[JackH]

Hey all, still working on the II. The distributor pickup coil should be here later this week and I have also found that the ignition coil was bad so I got a new one put in. Anyway, I was wondering if anyone new if/what gas tanks are interchangeable on a 77-78 mustang because a new OEM one is $250. The ones for a 74-76 MII are $165 on ebay so I was wondering if that would work? To my knowledge the only reason they changed them halfway thru the ii was because of the whole pintos explosion crisis. Also if I did do that, would I need a new filler neck, sending unit? Mine is a 2.8L V6.

Thanks for the advice,
Jack H.

 

[85GTStangGuy]

Didn't the earlier MII's have the gas filler lower on the rear quarter, whereas the later ones had the filler higher up? Don't know the by-the-years breakdown, but just wondering if that is the reason for the different tanks. It may have been more than just a change in filler necks....

 

[LILCBRA]

If I remember correctly there was a slight change to the top of the tank to accommodate for something. I know the early tanks don't fit the later cars though, I tried since the tank in my 77 was full of pinholes on top and I had a 76 parts car that I tried to swap from. From there I think there are only 2 - 3 options. 1st one is probably the most expensive as you've pointed out - find a replacement. A quick Google search revealed one through PartsGeek.com here. Another option is to swap in a fuel cell, but that may be just as expensive and most likely less practical, depending on what you could come up with. The third option is what I did way back when - the Fox cars use a tank with a similar shape but required modifications to the car as well as the tank. I have a thread in the stickies under the tech link: http://www.stangnet.com/mustang-forums/threads/fox-fuel-tank-in-a-ii.820975/

I also have a short YouTube video that I tried to illustrate what all needs done.
View: https://youtu.be/pEHGqIu7FJQ?si=04XOC7mG8Nq1Ezqm

That path required welding on the fuel tank. Be careful if you try this on a used tank as I did, but I didn't have any problems. I got my tank from a salvage yard, but there are plenty of options for new. Mine was from a fuel injected car, but I kind of wonder if you were to get one made for an early non-EFI car, say a 79, if the filler tube would work and you wouldn't have to really do much to install the II's pickup. Those can be purchased new from LMR. They have 2 options for non-EFI, the early 79-81 and the 81-86. You could also opt to install the later tanks and just use a Fox pickup and pump in conjunction with a fuel pressure regulator, but IIRC the fuel level sender has different ohms settings as compared to the II so your gauge might not work properly.

I guess there's a 4th option that I know has been done, but that requires even more modifications to the car: cut the floor from the hatch/trunk and install an early Mustang tank. That requires relocating the filler, using a flip down license plate and sealing off the original filler.

Didn't the earlier MII's have the gas filler lower on the rear quarter, whereas the later ones had the filler higher up? Don't know the by-the-years breakdown, but just wondering if that is the reason for the different tanks. It may have been more than just a change in filler necks....

You are correct, the 74s had the filler neck located lower on the quarter than the 75-78 cars, but to my knowledge the tanks are the same from 74-76.

 

[LILCBRA]

The third option is what I did way back when - the Fox cars use a tank with a similar shape but required modifications to the car as well as the tank. I have a thread in the stickies under the tech link: http://www.stangnet.com/mustang-forums/threads/fox-fuel-tank-in-a-ii.820975/

I also have a short YouTube video that I tried to illustrate what all needs done.

That path required welding on the fuel tank. Be careful if you try this on a used tank as I did, but I didn't have any problems. I got my tank from a salvage yard, but there are plenty of options for new. Mine was from a fuel injected car, but I kind of wonder if you were to get one made for an early non-EFI car, say a 79, if the filler tube would work and you wouldn't have to really do much to install the II's pickup. Those can be purchased new from LMR. They have 2 options for non-EFI, the early 79-81 and the 81-86. You could also opt to install the later tanks and just use a Fox pickup and pump in conjunction with a fuel pressure regulator, but IIRC the fuel level sender has different ohms settings as compared to the II so your gauge might not work properly.

Actually, come to think of it, you'd need to weld the pick up location like I did, the Fox tank is installed backward compared to it's construction.

 

[JackH]

If I remember correctly there was a slight change to the top of the tank to accommodate for something. I know the early tanks don't fit the later cars though, I tried since the tank in my 77 was full of pinholes on top and I had a 76 parts car that I tried to swap from. From there I think there are only 2 - 3 options. 1st one is probably the most expensive as you've pointed out - find a replacement. A quick Google search revealed one through PartsGeek.com here. Another option is to swap in a fuel cell, but that may be just as expensive and most likely less practical, depending on what you could come up with. The third option is what I did way back when - the Fox cars use a tank with a similar shape but required modifications to the car as well as the tank. I have a thread in the stickies under the tech link: http://www.stangnet.com/mustang-forums/threads/fox-fuel-tank-in-a-ii.820975/

I also have a short YouTube video that I tried to illustrate what all needs done.
View: https://youtu.be/pEHGqIu7FJQ?si=04XOC7mG8Nq1Ezqm

That path required welding on the fuel tank. Be careful if you try this on a used tank as I did, but I didn't have any problems. I got my tank from a salvage yard, but there are plenty of options for new. Mine was from a fuel injected car, but I kind of wonder if you were to get one made for an early non-EFI car, say a 79, if the filler tube would work and you wouldn't have to really do much to install the II's pickup. Those can be purchased new from LMR. They have 2 options for non-EFI, the early 79-81 and the 81-86. You could also opt to install the later tanks and just use a Fox pickup and pump in conjunction with a fuel pressure regulator, but IIRC the fuel level sender has different ohms settings as compared to the II so your gauge might not work properly.

I guess there's a 4th option that I know has been done, but that requires even more modifications to the car: cut the floor from the hatch/trunk and install an early Mustang tank. That requires relocating the filler, using a flip down license plate and sealing off the original filler.



You are correct, the 74s had the filler neck located lower on the quarter than the 75-78 cars, but to my knowledge the tanks are the same from 74-76.

I appreciate the advice and experience! From what I could price out, going with a fuel cell with all of the lines an fittings would require slight cutting and cost about $300-$350. I have no way of knowing if my fuel sending unit works but I CAN see if it is getting voltage I guess...I really don't need a gas gauge anyway because I can't go to far off base before having to go back again lol. It seems replacing the electric fuel pump and going with a OEM tank is best I guess.

Thanks,
Jack H

 

[extra_stout]

have no way of knowing if my fuel sending unit works but I CAN see if it is getting voltage I guess...

The fuel sending unit has a variable resistance, which is measured by the fuel gauge. You need to measure the resistance at the wire connector at the fuel tank. The values for full and empty are given in the shop manual.
I cleaned my tank and sending unit and its working. My car was sitting for 20 years with fuel in the tank...

 

[LILCBRA]

If you chose to go with a Fox tank and Fox electric pump the sensor could be added at a later date. The resistance range for those sending units are 145 Ohms Full 22 Ohms Empty as referenced from LMR's site here. The II's resistance range is less as quoted from another old thread here:

73 ohms empty and 10 ohms full, give or take...

I guess it would depend on your budget and what you could find through a salvage yard or through places like Ebay and Craigslist/Marketplace, but the best solution is probably going ahead and spending the ~$175-200 on a new replacement tank instead of going with a different style (fuel cell, Fox tank, etc....). There were no replacement tanks available when I did mine, they are a relatively recent offering. But given the supporting pieces and extra work, the others will most likely keep increasing the total amount of money involved. So I guess I retract my statement on this path probably being the most expensive UNLESS you're able to find a Fox tank in a salvage yard for ~$50..... but even then it might be a wash. I will add, though, that if you were to EVER decide to install fuel injection, a Fox tank gives you a couple options more easily than a stock tank.

Side note: if you happen to have Amazon Prime and can take advantage of free shipping, you can get a new tank for $166 and some change....

 

[JackH]

If you chose to go with a Fox tank and Fox electric pump the sensor could be added at a later date. The resistance range for those sending units are 145 Ohms Full 22 Ohms Empty as referenced from LMR's site here. The II's resistance range is less as quoted from another old thread here:



I guess it would depend on your budget and what you could find through a salvage yard or through places like Ebay and Craigslist/Marketplace, but the best solution is probably going ahead and spending the ~$175-200 on a new replacement tank instead of going with a different style (fuel cell, Fox tank, etc....). There were no replacement tanks available when I did mine, they are a relatively recent offering. But given the supporting pieces and extra work, the others will most likely keep increasing the total amount of money involved. So I guess I retract my statement on this path probably being the most expensive UNLESS you're able to find a Fox tank in a salvage yard for ~$50..... but even then it might be a wash. I will add, though, that if you were to EVER decide to install fuel injection, a Fox tank gives you a couple options more easily than a stock tank.

Side note: if you happen to have Amazon Prime and can take advantage of free shipping, you can get a new tank for $166 and some change....

I do have prime but mine is a 78 so it's my understanding that the 74-76 tank wont work right? I think you are correct though and I did find a 77-78 tank for around $245.

 

[LILCBRA]

Sorry, forgot you said it was a 78....