I've done many repairs on fuel gauges and senders for friends and myself on our Ford Falcons.
It took a bit of trial and error, but it was found that most problems have to do with a
poorly grounded Fuel Gauge/Sender system.

I found the Econoline to be pretty similar (my cars are '61 to '63, Econo is a '61) to the Falcons
so it was not too hard to make repairs on the Econoline.

Here is a basic list of stuff to find out if each part is working on its' own. At the end of
this post, I show how to modify the fuel sender to have a good ground.


I've got an Econoline Pickup and the Gas Gauge is broken.
Here is what I do:

-You will need a voltmeter with a needle readout, try not to get a digital one, by they will work too.
-A test light.
-2 batteries, I use AA, taped in series (end-to-end.)
-wire with "alligator" clips on the ends (you can use tape but not as easy.)

TEST VOLTAGE SOURCE GOING INTO THE CVR
The Constant Voltage Regulator (NOT the voltage regulator for the generator! ) is right behind the
speedo. It's a little tin box, has two leads, Black/Green wires. Test the incoming wire for voltage
first. Incoming is a SINGLE Blk/Grn wire, outgoing is a single B/G wire that splits into a double B/G
wire for both Temp and Fuel.
Connect meter to the incoming post and ground the other lead to dash metal. Turn IGN key to "on."
You should get about 11-13 volts, steady.

ALL THE CVR DOES IS TURN 12V TO 5V (on average) *the 5V is an oscillating voltage turning
"off" and "on" by itself, about 2 times a second from 1V to 12V (roughly.)

TEST VOLTAGE LEAVING THE CVR
Connect meter to outgoing post on the CVR and ground the meter again. Turn the key "on."
You should get a voltmeter that bounces up and down between 1 and 12 volts, it looks like a
heartbeat. Average voltage is 5 volts which is what both the gauges need to operate.
If a Meter is not available, you can rig a 12v light from the outgoing post on the CVR to GND, and
the bulb should dim and brighten, like a heartbeat. If the CVR shows this heartbeat, it is probably
good.

TEST THE FUEL GAUGE
You can force your Fuel and Temp gauges to work, just add voltage and watch them go.
Connect the "AA" batteries in series between both posts of the Fuel Gauge. The gauge should go to
almost full in about 30 seconds or so. This is also true for the Temp Gauge. Check these off if
the gauges work, and continue looking...

TEST THE WIRE GOING TO THE GAS TANK
Assuming the Fuel Gauge is connected and the Gauge Cluster is re-installed in the Dash:
Pull the wire off the Fuel Sender Unit and ground this wire to nearby clean metal. Momentarily
turn IGN to "on." Fuel Gauge will quickly go to Full. (Shut down quickly after verifying gauge
function. The gauge is supposed to handle 5 volts not 12+.) Note: NEVER connect 12V to the
Sender as some sort of test, it will fry. If the gauge went to "FULL" then the wiring from the
dash to the tank is good...

TEST THE GROUNDS
In my experience this is what the problems usually end up being at least in part.
Check 4 contacts.
1. Battery POS to Starter Solenoid (if your Econo Starts/Runs then it is a foregone conclusion.)
2. Battery NEG to Engine Block, usually at the front of the block. (CLEAN both ends up real good!)
3. Engine Block to Body (This is usually at the rear of the block, NOT directly connected to #2 above,
to prevent "noise.") This one gets neglected! Some cars will run without one, ha, but not at their best.
(ie. lights will flicker, etc. The car will act "possessed.")
4. Body to Fuel Sender, from what I've seen on the Econolines, this connection can get pretty messed
up. Typical route is the Fuel Sender, to the Locking Ring, to the Tank itself, to the Body. (LOTS of
places for rust and crud to reduce the continuity!)

You NEED these four GROUND connections to make things work!!!

I'd suspect #3 and #4 as the common culprits. Take your time cleaning and making BARE metal contact.
I use dielectric grease (looks like Vaseline) on the contact points to make them stay good for longer.

In the photos below, I make a wire connecting the sender directly to the body to get a good GROUND
as per #4.

Most guys go right for replacing the Regulator or the Sender. I've found that those parts seem
to last pretty well over time, but still need to be checked.

In my case, the previous owner said, "Gas gauge doesn't work, just carry a gas can for reserve"
which was unacceptable to me. ALL OF THE ABOVE CHECKED OUT FOR ME (except for doing
#4)


The stock 50-year-old sender pulled out. I have found the replacement Sender Units
are NOT nearly as good in quality to the original. Two common points of failure are
the Float and the Rheostat.


The Float was full of fuel! (see wet spot.) The float can also fill with sediment.


Replacement floats are widely available online. Plastic is typical and work well.

Note: I also CAREFULLY opened up the Rheostat (unbent the 3 clips to the lid.)
Only inspect the fine wires, and clear out the sediment. Mine was 1/3 full of
crud. The rheostat wires looked new. The slider contact was rubbing a little
light (but it should NOT rub too hard,) so I bent it a bit with tweezers until I
could just hear contact through its' range.

If the Rheostat is damaged, the whole sender needs to get replaced. I noticed the
new ones do not have the quality or good design of the rheostats of the originals.
The design of the windings looks totally different, and the original has much higher
resolution in the last 1/4 tank.
Also the action of the originals is superior. Try hard to get the original to work.

GROUNDING THE SENDER TO BODY (per #4 above)

If you have a Stud Gun for pulling dents, you are in luck. If not you can go to any
autobody place and they can fuse a stud onto your sender for almost nothing.

This is to NEVER be done with the Sender in the tank, that could cause an explosion.
Use common sense. This thread is only a guide to show what I did.

Size does matter...

Using a OEM bullet-style connector, squeeze down the internal metal sleeve to fit
tightly on the Welded Stud. I spot weld the largest diameter stud I can find, 1/8"
would be a minimum.


Test fit. Should be pretty tight. I trim the stud down to about 3/4 inch stickout.


Eyelet fitting placed on other end of ground wire. I solder and shrink tube all
my connections. Crimp connections are pretty much a joke over time with
vibrations and crud...


Sender back in. I use Permatex High Tack on both tank and sender surfaces.
This sealer is gas proof. I find most replacement o-rings to be poor fitting. I
end up using originals if they look to be in good shape.


Note the trimmed stud ready for the ground wire.


It is super-important to get clean, bare metal on the chassis/body!


I use a star washer and dielectric grease for the best connection possible.
It is this Sender-to-Body connection that is the "weak link" in the Gas Gauge system.


Ground established.


Bingo! The gas gauge works again. Thinking about how many years it
didn't work.

This effort only cost me a float and my time. I can't stand not having a working
gas gauge in my Daily Drivers!!!

George

You guys are lucky. The 1st gen Chevy senders are not available for sale and once in a while you'll see one on ebay that sells for $200. I rebuilt mine using a truck rheostat but it reads 1/4 tank when empty. I was lucky to find a 65 in the junk yard and got the sender in good condition but want to make the rebuild work. Donivan and a few others put a lot of time into it, but I have a backup. I have to bend the float arm a little to see if I can get it to read empty on E. It reads full when it's full but I ran out of gas once when testing it.....I carry a gallon just for that reason.