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Discussion Starter #1
Hey, smart car guys! I need help, please!
I replaced the 16 gal tank in my 68 coupe. Did alot of suspension work too, so the stance is not stock. Anyway, I have ran the new tank dry of fuel, and have to date only been able to get just over 9 gallons back in it. I fills up the filler tube and stops. The gauge reads just over half tank. With a 289 and 4.11 rearend 9 gals don't get me far. It is almost like there is an large bubble in the front portion (away from filler tube) of the tank that won't vent out to allow fuel to fill. Any ideas?
Thanks much!
 

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I'm thinking your tank sending unit is out of calibration and your tank is full. The back end would have to be way lower than the front to create an air pocket in the front of the tank so I don't think that's the problem. Did you replace the sender when you changed out the tank?
 

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Discussion Starter #4
Sending unit, gas lines, everything is new. And, don't forget, I ran it dry...out of gas 5 miles from home!!! hehheh...took only 9 gallons and would take no more. I dont trust the gauge...but I think it works too, cause it does read just over 1/2 tank. hmmm! now what?

Thanks though...stance is good, there is a photo on her somewhere.
 

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No idea! :loco:
 

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"Ran it dry"...

Meaning until it stopped, or until the tank was really empty?

Run "dry", inspect tank to see if fuel actually exists, visually or dip a rod into the tank to see if any fuel remains.

If tank has fuel:

- Drain tank (hopefully you have a drain plug). Pull sender and make sure it it positioned correctly.

If no fuel:

- no clue. The filler neck and tank are so large that the odds of some blockage stopping the tank from filling at 9 gallons is slight... the nose of the car would have to be rediculously high to get an air bubble in the front of the tank...

The fact its reading half when full would make me think the sender is in wrong... or bent...
 

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This may not be your problem since you said you had a completely empty tank and could only get 9 gallons in but...
Way back when I was driving my 68 daily, the gauge would never read more than half. I tried everything and then one day ran across the voltage regulator on the back of the gauge cluster. I changed that and, viola, full tank.
 

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Boss68 said:
I'll bet the pick up tube and float are too far from the bottom of the tank after the new installation, sitting in wrong position.
As was mentioned, check and see if it is still partially full when the fuel stops flowing.
+1
 

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If the car ran out of gas, and he said all he could get in was 9 gallons, I dont see how that is a sender unit. The sender is to small to block the tank inlet.

Have you tried filling the tank slower? Have you had any work done to the car? My first mustang, back when I was 16 had some work done to a qtr panel and the shop put a rag in the filler neck, but left the cap on. first fill up gas came pouring back out.
 

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Just for the sake of asking, did the new tank have tape over the filler opening and if so did you remove it completely?
 

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fast68back said:
If the car ran out of gas, and he said all he could get in was 9 gallons, I dont see how that is a sender unit. The sender is to small to block the tank inlet.

Have you tried filling the tank slower? Have you had any work done to the car? My first mustang, back when I was 16 had some work done to a qtr panel and the shop put a rag in the filler neck, but left the cap on. first fill up gas came pouring back out.
Well, this is how it can happen.

The sending unit is at an angle , the angle has the filter off the bottom and the float is also off the bottom.
Sooooo it is off the bottom by 9 gallons (18 gallon tank) he runs out with 9 gallons left in the tank, theeeeen fills in 9 gallons (eqauling the max 18) it is full "hey it is only taking 9 gallons, what up with that" , well "that" is up with "that".

If that filter is off the bottom so is the float , simple as that. I bet when it runs out you have 9 gallons still in the tank :)

EDIT: 16 gallon tank that runs empty with 7 gallons due to sending unit being sideways.

I should ask if the sending unit has ever been removed. Very easy to get lined up wrong if it does not have alignment tabs.
 

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Its a 16 gallon tank, but I see your point. The pickup is at the bottom of the tank, for the tank to be almost half full and the car run out of gas would be way out of line.

IIRC, the sending unit will only go in one way, no? I would think you could look under the tank and see the angle of the where the fuel line connects to the sender and determine if the sending unit is not installed correctly.

http://www.mustangsunlimited.com/ProdImages/9275A-B.jpg
 

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Rick you're right. If the elbow isn't pointed the right way he could tell at a glance if that were the problem or not.
 

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Discussion Starter #17
OKAY CHECK IT OUT!
All the responses are overwhelming. Don't know if we are there yet. I kinda like the idea that maybe the sending unit is installed wrong...just don't know why fuel to the pump would stop with 9 gallons still 7 gallons still in the tank. It is possible though, that there was still gas in the tank. Definitely wasn't getting to the engine though. I will check that out.

The tank vents through the cap, no problems there. The car sits nice. No blockage in the filler tube, no objects (or plastic) in the tank.

Maybe it is the fuel fairies...but I gotta get it fixed. Thanks, let me know if you think of anything else. Great thread...thanks!
ED
 

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just don't know why fuel to the pump would stop with 9 gallons still 7 gallons still in the tank.
Real quick sketch. Black is sender in correct position, can get to all gas.

Red is sender rotated in wrong position, keeping float and screen up off bottom of tank where they belong. Area under green line is gas that can not be used... thus making a "dry" tank fill in 9 gallons as 7 gallons is in the tank, but under the line... and unseen to the pump.



HTH
 

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Discussion Starter #19
Okay, okay...we might be on to something. Dalorzo f, your drawing helps me understand the concept.

I crawled under the car. If I go by photos in catalogs, I think I have the sending unit installed at the proper angle, however, I can't be sure. The tube where I fasten the gas line, as I face it, is standing at about 2:00.

I dont remember if there was only one way it could be installed, and to look at it now, it appears that there are three possible angles of installation. That means two could be wrong. Anyway, it won't hurt to pull the sending unit to check its operation.

Soooooo...I hate to keep you all waiting, but- I am going to run it until it stops (no fuel), then check the contents of the tank, rather than pull the plug and drain the tank now. And, we are in a bit of a rainy spell here in NW Washington,and this car doesn't start in the rain...know what I mean?

Of course, this could eat away at me and I might decide to go drain the tank....hehheh!

I will definitely let you know what I find out though...give me a few days.

I so appreciate the help...I hope this does it!
-ED
 
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