Fuel Syst Overhaul...

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70DusterBob

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I ordered the Right Stuff's version of new fuel line, front to rear, a new sending unit and a new tank. Anyone deal with them before? Probably should have asked this earlier, but I am trying to get my car running, been down for two years. Spent a gob of money on a build, 408/727 then the fuel line when to crap after sitting two years. The sending unit wasn't working, so I replaced it, the tank had a liner in it, and the line is full of rust. Anyone been here know what to do, what to buy from who? I haven't opened any of the right stuff parts yet.

Thanks
 
I have used Right Stuff brake lines. They were fine.

But I don't think anyone makes a good replacement sender unit for A-bodies. Look at it beside your old one. You will see that the float arm is shorter and a different shape, and the pivot point of the arm is in a different location. Also, the little circuit board that the pointer runs on is also a different shape and size (it may be concealed inside a canister). This is because these firms are supplying a "generic" sending unit. It may read correctly at E and F (or can be adjusted to do so — that may take adding a resistor, or bending the arm) but in between it will not be remotely accurate, because it is not "programmed" to compensate for the fact that the upper half of the A-body fuel tank has a massive cut-out for the spare tire.

To read correctly, it would need to compensate for the fact that when the float is at the midpoint between bottom and top, there is only about 1/3 tank of fuel remaining. The original one did this by variably spacing the windings on the circuit board. Unfortunately, this is the part of the original that wears out and causes it to fail.

If you have a new tank and a new line, that should take care of your rust problems. But I went to great lengths to find a good original style sender, and refurbished it with a new float and new sock.
 
I have used Right Stuff brake lines. They were fine.

But I don't think anyone makes a good replacement sender unit for A-bodies. Look at it beside your old one. You will see that the float arm is shorter and a different shape, and the pivot point of the arm is in a different location. Also, the little circuit board that the pointer runs on is also a different shape and size (it may be concealed inside a canister). This is because these firms are supplying a "generic" sending unit. It may read correctly at E and F (or can be adjusted to do so — that may take adding a resistor, or bending the arm) but in between it will not be remotely accurate, because it is not "programmed" to compensate for the fact that the upper half of the A-body fuel tank has a massive cut-out for the spare tire.

To read correctly, it would need to compensate for the fact that when the float is at the midpoint between bottom and top, there is only about 1/3 tank of fuel remaining. The original one did this by variably spacing the windings on the circuit board. Unfortunately, this is the part of the original that wears out and causes it to fail.

If you have a new tank and a new line, that should take care of your rust problems. But I went to great lengths to find a good original style sender, and refurbished it with a new float and new sock.

That explains it. I had an after thought sending unit in it and it did exactly what you have explained. Thank you!
 
Hey MVH,

Could you explain to me how the gauge miscalculates so I know how much, approximately, fuel I have in the tank. The one I have in the tank now goes to full, but then like at 3/4 of a tank it drops to less than a half, then to a quarter real quick then to empty, but there is still a half a tank in it when it reads empty. It has a sunken float. It is plastic. I made sure to get a brass float this time. But I am wondering how I can keep track of my fuel with a wacky gauge reading. If you have any idea what 3/4 tank would mean, what 1/2 would mean and what 1/4 means with a new float in a new after market sending unit, I would appreciate it. Thanks
 
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