Removing fuel sending unit

JC Mustang · Apr 23, 2009

My tank is empty right now, so now is a good time to get to the bottom (pun intended) of my fuel gauge issue. I'm trying to remove the fuel tank sending unit, but the retainer is quite the pain. There seems to be no way to get purchase on the tiny "fins" that raise off of it, especially in the contorted position I must be in to reach the thing in the first place. Any tips?

golf4283 · Apr 23, 2009

a pliers and a bit of patience. Shouldn't be too hard to get at unless it's all crudded on. Just grab one of the tabs with the pliers and unscrew it.

Capt Dan · Apr 23, 2009

A flat-head screwdriver and a hammer.

Tap on one of the tabs to get it spinning. Only has to turn less than 1/3

JC Mustang · Apr 23, 2009

Capt Dan said:
Only has to turn less than 1/3

good to know...once it breaks loose it'll be out

golf4283 · Apr 23, 2009

yea it's just a lock ring. nothing fancy. I would order a new seal though and make sure to put a bit of silicone or other sealant on it so it doesn't crack over time.

JC Mustang · Apr 23, 2009

Some penetrating oil and a couple hours did most of the work after a good five minutes of what I can only call "careful wailing" didn't do the trick.

The unit appears visually to be in good condition, with free movement of the float and no foreign bodies. Now, is there a way I can test it? I assume the gauge measures the resistance? I can't seem to figure out how exactly I can test that though, my meter won't show any change unless both probes are on metal that goes to the gauge terminal. The original problem is that my dash fuel gauge reads about 3/4 after a fill up and goes to empty when there is still about 1/4 of a tank.

Mil1ion · Apr 23, 2009

DANGER

onLy use a brass punch to prevent sparks...not a steel tool like screwdriver...or KABOOOOOOOMMMMMM

you can use a jumper wire from harness to the SU in a comfortable place in the drivers seat so you can watch the gauge as you move the lever by hand

you can also use an ohmmeter to check the resistance of the SU

Re: Ford Gauges

They are calibrated to read empty or zero at 70 Ohms of resistance. The full or maximum reading will be at 10 Ohms. All of the senders are calibrated for this 70-10 Ohm range. The fuel sender at 1/2 tank should read 40 Ohms.

~Ohms >> Reading
150 >> No movement - same as if the wire were broken or disconnected
73 >> Off scale 1/2 needle width below E
68 >> E
50 >> 1/8
26 >> 1/2
15 >> 7/8
12 >> F
10 >> Off scale a needle's width above F

Since the gauges are all a little different these numbers are not exact, but close. Shorting the sender wire to ground is a way to test the gauge but since its Zero Ohms to ground it will be overheating the gauge if you keep the short there for very long.

Even with an empty tank the needle will move just a bit when the key is turned on so that it is at the 73 Ohm position. That tells you the wire is not broken. With the 16 gallon tank and an original Ford float properly adjusted the first 1.5 gallons does not change the gauge reading; Ford's way of getting you to fill up early so you won't run out of gas. Likewise the last gallon does not change the slightly more than F reading; makes you feel good that the needle didn't drop after the first 10 miles of driving.

JC Mustang · Apr 24, 2009

OK, I shorted the sending wire to ground and the gauge went right up to full, so it's the sending unit and not the gauge at fault. Do I bother messing with this unit, replacing float or anything else, or just get a new one?

golf4283 · Apr 24, 2009

They aren't really that expensive so I would say just order another. Make sure to order the correct year.

Mil1ion · Apr 24, 2009

Pretty hard to go wrong.....

Part # COAZ-9202-A

The application has numerous cars

Want an N.O.S. one?

1 left at ED BENNETT FORD PARTS LEBANON, PA 1704 (717) 272-8762

rob289c · Apr 25, 2009

My sending unit/gauge reads just like yours does. A few weeks ago I drained the tank and tested the sending unit with the ohm meter and it read close to the previous post (09-76) . I bent the sending unit arm until the gauge read full when the sending unit was forced to full, and read empty when the sender was forced to the empty position. After reinstalling and filling the tank one gallon at a time and recording the gauge position after each gallon, it wasn't any better. Tonight I ran out of gas on the way home (near a station...whew!) so tomorrow I'm going to repeat the drill. This time I'm going to bend the arm so the gauge reads past full so maybe it will read correctly once reinstalled. I don't like it only going to 3/4 when full and not knowing how much fuel is in the tank when on E. I'll report back tomorrow after the job is complete.

2+2GT · Apr 25, 2009

rob289c said:
My sending unit/gauge reads just like yours does. A few weeks ago I drained the tank and tested the sending unit with the ohm meter and it read close to the previous post (09-76) . I bent the sending unit arm until the gauge read full when the sending unit was forced to full, and read empty when the sender was forced to the empty position. After reinstalling and filling the tank one gallon at a time and recording the gauge position after each gallon, it wasn't any better. Tonight I ran out of gas on the way home (near a station...whew!) so tomorrow I'm going to repeat the drill. This time I'm going to bend the arm so the gauge reads past full so maybe it will read correctly once reinstalled. I don't like it only going to 3/4 when full and not knowing how much fuel is in the tank when on E. I'll report back tomorrow after the job is complete.

That's not how these are adjusted. If the sender is working properly, the E and F can be adjusted using the small gears visible through the small adjusting holes on the back of the gauge. It's a pain, but great accuracy can be achieved.

JC Mustang · Apr 25, 2009

rob289c said:
My sending unit/gauge reads just like yours does. A few weeks ago I drained the tank and tested the sending unit with the ohm meter and it read close to the previous post (09-76) . I bent the sending unit arm until the gauge read full when the sending unit was forced to full, and read empty when the sender was forced to the empty position. After reinstalling and filling the tank one gallon at a time and recording the gauge position after each gallon, it wasn't any better. Tonight I ran out of gas on the way home (near a station...whew!) so tomorrow I'm going to repeat the drill. This time I'm going to bend the arm so the gauge reads past full so maybe it will read correctly once reinstalled. I don't like it only going to 3/4 when full and not knowing how much fuel is in the tank when on E. I'll report back tomorrow after the job is complete.

Here's my question - how were you able to test the resistance? Any time I put my tester's probes on any parts of the sender I either get no resistance (if they are both along the line to the sender) or no movement.

rob289c · Apr 26, 2009

Put one lead of your ohm meter on the terminal that the gauge wire goes on and the other lead on the part of the sending unit that would contact the tank if it were installed. Move the float arm slowly through its range of travel and you'll see different resistance readings on your ohm meter. should be .10 - .73 or close to that.

rob289c · Apr 26, 2009

2+2GT - I never knew about the adjustment holes on the back of the gauge. I've scoured the archives of this forum and the internet in general on this subject and never came accross this method. They all talk about bending the float arm lower to get the gauge to read higher. This will definately be worth a try. Is there a procedure for doing this? Should the tank be completely empty or full and how are the "gears" adjusted? Is there a screw head?

rob289c · Apr 26, 2009

Today I drained my tank (again), removed the sending unit, bent the arm slightly downward, reinstalled, then re-filled tank one gallon @ a time and recorded needle position with each gallon added. Now the gauge reads full when the tank is full. I'll monitor as I use fuel and re-fill. It's a lot beter than it ever has been but I'd still like to adjust the gauge as 2+2GT advised.

2+2GT · Apr 26, 2009

rob289c said:
2+2GT - I never knew about the adjustment holes on the back of the gauge. I've scoured the archives of this forum and the internet in general on this subject and never came accross this method. They all talk about bending the float arm lower to get the gauge to read higher. This will definately be worth a try. Is there a procedure for doing this? Should the tank be completely empty or full and how are the "gears" adjusted? Is there a screw head?

Ideally, you should have the sender out, but connected, so you can check both E and F.

The gauge will need to be out of the panel, which is why this is such a pain, and you will need to connect them with alligator leads so everything works. In the two holes in the back of the gauge you will see the teeth of the adjusting gear. Use a small torx or in a pinch a phillips screwdriver to adjust the E with the sensor all the way down, and the F with the sensor all the way up. Check it a few times at both ends, because adjusting it apart is easy, but getting to that point is a major pain.

JC Mustang · Apr 27, 2009

golf4283 said:
yea it's just a lock ring. nothing fancy. I would order a new seal though and make sure to put a bit of silicone or other sealant on it so it doesn't crack over time.

Do you mean like Permatex #2 (gasket sealant)?

rob289c · Apr 28, 2009

GT 2+2: Thanks for the info on gauge adjustment. I'll give it a shot one of these days...maybe not right away but at some point I will.

JC: I used Permatex #2 in the area where the gasket contacts the tank. It holds the gasket in place while you get the sender positioned. My locking ring doesn't seem to hold the sending unit tight enough against the tank. Right now it's not leaking but if I move it a little it starts leaking. Both times I've had the sender out and reinstalled it and got it sealed up (after several tries) it hasn't leaked, it's just trying to get it to seal initially that seems to be a challenge. I'm always afraid that one day I'll go out in the garage and find up to 16 gallons of gas on my garage floor!

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