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The original fuel tank sending unit in my 65 had developed an occasional sticking point at about ¾ of a tank. Electrically it is fine, but the mechanical part is a little stiff.I ordered a replacement sending unit from Autokrafters (#C5AZ-9275J), but now my gauge registers “over full” when installed.

Interestingly enough, when outside the tank and plugged in, I can move the float arm on the replacement and get a corresponding reading on the gauge. Only when installed correctly does the problem occur. It seems as though it is grounding out, but the unit (regardless of original or replacement) is not designed to be isolated electrically from the tank. Got another sender and the results are the same.

My fuel gauge and instrument panel voltage regulator are new. Wiring is good. Electrically, it seems as though everything is fine in the circuit. As a matter of fact, I can move the float all the way down on the original sender, reinstall it and the float comes up to send a correct gauge reading of ½ full. I’m stumped. Any ideas?
 

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The original fuel tank sending unit in my 65 had developed an occasional sticking point at about ¾ of a tank. Electrically it is fine, but the mechanical part is a little stiff.I ordered a replacement sending unit from Autokrafters (#C5AZ-9275J), but now my gauge registers “over full” when installed.

Interestingly enough, when outside the tank and plugged in, I can move the float arm on the replacement and get a corresponding reading on the gauge. Only when installed correctly does the problem occur. It seems as though it is grounding out, but the unit (regardless of original or replacement) is not designed to be isolated electrically from the tank. Got another sender and the results are the same.

My fuel gauge and instrument panel voltage regulator are new. Wiring is good. Electrically, it seems as though everything is fine in the circuit. As a matter of fact, I can move the float all the way down on the original sender, reinstall it and the float comes up to send a correct gauge reading of ½ full. I’m stumped. Any ideas?
One year manufacturer's warranty against manufacturer defects as long as the unit is not modified in any manner. Any damaged or defective unit should be sent back to Auto Krafters where it will be forwarded to our manufacturer for quality control inspection. A replacement unit will be provided at no charge plus shipping.


Features and benefits over OEM and competition: Support brackets are not spot welded to the top plates, eliminating the potential for leakage that occurs with current products on the market. All units are manufactured entirely from stainless steel.


This is the highest quality reproduction fuel sending unit on the market today. Due to this new material, the unit is less susceptible than the OEM or competitor's products to corrosion from new fuels.
Although a repro, it sounds like a quality part. Its' sending a signal that causes the gauge to read full when the tank is not is indicative of a defective sender (plus considering your description of replacement). Do they have a Tech Line?
 

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Discussion Starter · #3 ·
I sent Autokrafters an email and am waiting for a reply. In the meantime, I was hoping that someone on this great forum would be able to shed some light on the problem. Any similar experiences out there?

Sure, my first thought is a bad sender. But this is my second try, with the first one bought in February and the second just this month. It's unlikely that they are from the same batch. What are the odds that they are both bad?
 

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sounds like the arm is rotated or something- i dont recall, but can the insert be rotated in the tank?

take a look at how the float hangs on the old one at empty, and which way the fuel line sticks out, and make sure the fuel tube is pointing the same way on the new one installed in the tank... if its same, I'd pull it back out and see if it was built wrong
 

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One year manufacturer's warranty against manufacturer defects as long as the unit is not modified in any manner. Any damaged or defective unit should be sent back to Auto Krafters where it will be forwarded to our manufacturer for quality control inspection. A replacement unit will be provided at no charge plus shipping.
You bend it... You buy it.
 

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If it were me and I had one sender that showed 3/4 and another that showed overfull, I'd use both of them :)


Alternatively, here is some good info if you were thinking of doing some adjusting.
Fuel Tank Sending Unit Tech - FORDification.com
 

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You say when you have the sender out of the tank it reads correctly but you don't say if you have the sender grounded when checking.
 

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I had a new sender in my '66. It was wired backwards for my stock 2 wire plug. I reversed the connection. Ron W
 

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If you want it FIXED you do one of the following, provided that the unit is not grounding out like your surmised in your original post.

A: Bend the arm to get proper level indications.

B: Shorten or lengthen the float arm until you achieve the desired results.

Some units come with an adjustable float arm for long depth and or thick short tanks versus long thin tanks.

Sending unit form MACS to replace 55/56 Ford sending unit has S/S rod that you put in test and adjust to work the gauge accordingly.

On the 55 Frankenford I had the tank out and exactly half full of water (ten gallons measured from milk jug :)). I adjusted gauge to show half full. I used long jumper wires from OEM harness and had the tank sitting on bench outside door while watching gauge with each installation.

Once it read half I filled it all the way to be sure it read full on the gauge, then I emptied all but 2 gallons to be sure that on E the tank still had a little fuel, then called it a day and drained the tank ind reinstalled it when it dried out.

Sometimes BENDING the float arm is a must. The bent arm does NOT void the warranty of the unit.
 

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The bent arm does NOT void the warranty of the unit.
So... You will be willing to reimburse the poster once the vendor tells him to suck air?

Damn you are a nice guy... :tup:
 

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Discussion Starter · #15 ·
Thanks for all the good advice so far. I'm pretty convinced that its electrical though. I can plug in either of the aftermarket senders and insert it into the tank without allowing it to touch the tank itself, kinda like playing the old game of "Operation", and the guage will read a reasonable level. Once I touch the sender to the tank, the damn red nose lights up and the guage pegs over full.
 

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Then you may have an ill wired unit. Send it back for replacement.

Do you still have your Original? Hi I'm Sparkles, I'll help you with your electrical :)

The Fuel tank is grounded but not very well, which is why there is a ground strap male blade coming off your sending unit's body.

The Yellow wire with White stripe carries about 3.5 volts just like all the other dash instruments.

Kultulz may not understand the operation in order to be able to describe to you what happens but I will try:

The wire goes to the connecting wire in the sending unit. The FULLER your tank the more voltage you have going to ground, the hotter the Dash Gauge gets the higher the needle goes.

THE LOWER the level of fuel the less voltage going to ground the dash unit get's less current flow thus a lower reading on the needle.

Cool beans so far?

OK, That yellow wire carries voltage to the Small coiled wire in your sending unit It is INSULATED from all other metal contact in the tank.

Your Float rod fixture is Grounded, and there is a points like head on a light spring that rides up and down the coiled wire at the sending unit which conducts the voltage to the ground. It's a Rheostat if you understand that terminology.

The Closer the points like head is to the beginning of the thin wire winding the less resistance and a higher reading on the gauge. The farther away the more resistance and the less voltage to heat the gauge and results in a lower level of fuel.

Now that you got a grasp (I hope) on the basics, you need to locate the ERRANT GROUND that comes into contact with the sending unit yellow wire with white stripe, or the coil winding you'll find under the protective covering of the sending unit, or you need to KEEP on sending it back to the company you got it from until they get it through their thick skulls that it's 'effing broken' :).

There is ONE wire you're dealing with, and it's Grounding somehow when you put it to the tank. That tells me the wiring is bad.

Earlier I thought it was simply giving you a crap reading level wise, and a bend is almost always what fixes those.
 

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Check the voltage at the sender wire and report back.
 

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If he has 12 volts at the sender when he grounds it it will go to full.
 

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Check the voltage at the sender wire and report back.
You're looking for about 5.5 volts on the disconnected YL/WH wire with the key ON (RUN). While you're doing that, test the resistance of each unit you have. Disconnect the YL/WH wire at the sender terminal if it's installed. Attach your ohm meter probes to the terminal and the big top plate. You should see in the neighborhood of 73 ohms when "empty" and about 10 ohms when "full". BTW, once you get your gauge issue sorted-out, you can adjust the factory gauges to get good readings to match the new sender.

David
 
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