Different fuel sending unit installation in a 1966

2/2008 -- Received from Dennis, car 189

Fuel sending unit swap. I recently installed a new fuel gauge and matching sending unit (ohms had to match) in car 189. Original aluminum tank is in the car and the problem I had was trying to match the old 3 1/2 inch diameter unit to the new 2 1/2 inch diameter unit. I cut a piece of aluminum with an outside diameter of 3 1/2 inches and inside diameter of about 1 1/4 inches. (or just big enough to fit the new unit inside the tank)

 I used the old gasket, still in good shape under the new ring I cut then with self tapping screws, screwed the new unit to the new ring. Worked like a champ. All this work could have been avoided if they just made a sending unit with a 3 1/2 inch diameter top and matched the 1966 gauge I had. (Wishful thinking) I brought the old sending unit to at least 6 places including boat places and no one, even the old timers, even had a clue. One guy thought it may have come from a boat. Well that's my story and how I installed a new sending unit. Pictures coming soon...
 

Received 10/2005 from Ron, car #221, a 1967:

...The fuel sending unit in my Glassic is out of a 1967 Ford Bronco....

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THIS PAGE HAS TWO TOPICS. First, I replaced the fuel sending unit, and then ended up replacing the gauge since the sending unit turned out not to be the problem.  The gauge was bad. The info below pertains to car 1254, a 1978, but may be useful for other years too.

On a trip last fall, my 1978 Phaeton's gas gauge went ape. After filling the tank, the gauge pegged way over past full. In watching the miles per gallon, when the tank was ready for a refill, it had only moved down a bit - it still showed slightly above FULL.

I record my repairs for other NON-mechanics, like myself. The consensus was that the fuel tank sending unit likely went bad.  Inside the gas tank, sits an arm and float device - similar to the ball and float in a toilet. The float arm is connected to a variable resistor -- as the gas level goes down, the resistance changes, changing the amount of electricity going to the instrument in the dash, thereby causing the needle on the gauge to not travel as far.

Anyhow, the resistors go bad and the sending unit needs to be replaced. The car books say that replacing the sender is a "starting point" -- in my case it did  NOT solve the problem.

When my mechanic was too busy, I decided to try to change this myself.

Here is the sending unit. It sticks into the middle of the back of the gas tank. In order to remove it, you have to loosen the bold holding the strap that holds the gas tank, on the passenger side. In that way you can lower the tank some to get the unit out.  Note: later on, while fooling with this, I took a moto-tool and enlarged the notch in the back apron so that it was smooth and followed the arc of the sending unit. I touched up the edge with paint and it looked better and allowed me to remove the sender without loosening the tank. I used a compass to mark the car so it looks better than that white line in the picture above.

Tip #2 -- Don't smoke while doing this.

You unplug the two wires -- by pulling out on them in my case, and disconnect the gas line - tucking the gas line UP behind the bumper (a good bit of gas will dribble out of the hose if you let it lean downhill)  Then remove the unit by turning the ring that holds it counter clockwise about a quarter turn. There are three places where the ring wedges into grooves in the mounting place of the gas tank, and you turn the ring enough to free where it is wedged in.

Tip #3 -- I feel that there is a tool for this turning job -- could it be called a "spanner wrench" - I don't know, but I use a screwdriver and banged on one of the four prongs that stuck out of the ring to nudge it counter clockwise.  What I SHOULD have done is wedged a square shanked screwdriver between two of the adjacent prongs and used that as a fulcrum to twist off the ring.

You need to be careful doing that to be sure you aren't leaning your tool against the gas inlet or the electrical connector when you put pressure on it.

There is the unit out of the car. The most VALUABLE thing on the page is that ring on the bottom. Apparently, new sending units do NOT come with the ring, so don't lose it. Closest to you you see the three prongs on the ring that tuck into the slots on the gas tank. You put the ring in place in the three skinny places and then rotate it -- at the top of the ring, on the underside you can barely see one of the 4 prongs that stick out in the back -- those are to tighten it down.

The float is on the right, and the black thing is a filter.

Tip # 4 -- take your time maneuvering the sender in and out of the tank. I banged mine on the edge when removing  it and the filter fell off in the tank. Fishing it out was quite a trick.

Getting a replacement part.  I thought that would be the easy part. It wasn't. Nobody locally had ANY -

Tip # 5  This car uses a 1970 or so Ford BRONCO  sending unit, not a Mustang one. A Mustang sender fits in the opening, but the inside is different and designed for a deeper, smaller tank.  I do not recommend the substitution.

The above description came from a website wildhorses4x4.com/16.asp They had the correct item for $65 plus postage -- They also had those retaining rings for $9. There are other on-line sources too. I don't know these people -- they were the first ones I found using Google.

An order to them in March 2005 did not go well. They had been on backorder for quite some time (yet their website made no mention of that), they have no provision for quoting postage cost until after you order something, and they did not respond to my order until I sent a follow-up email. I would only suggest using them for reference info or perhaps ordering by phone.

Tip # 6 I ended up using Vaseline jelly to hold the gasket in place, and to slick up the parts to they would slip together without bunching up the gasket.

BACK TO THE MUSTANG unit:  The gas line to the engine is a metal line that seems, in my case to end about the middle of the gas tank above it. At first, I was going to just swing the hose around so that it approached from the driver's side, but it put too many bends in the hose, which probably should have been replaced anyhow.  I suppose I could have cut the metal tubing, flared it, and put on a new hose to approach from the drivers side.  I ended up having my welder cut off  the line ending on the Mustang sending unit and put it on facing the way the old one was facing. $12 for the welding job.

Tip # 7 -- Although I was able to bend the tube INSIDE the gas tank to match, when I tried to bend the outside part, the vice made a small leak, which I ended up patching with a piece of gasket and a hose clamp.

I only mention my use of the WRONG PART since Mustang parts are generally easier to find than Bronco parts, and I saved about half the money of a Bronco part - if you don't count my making myself crazy trying to make it fit right. Best idea?  Get a Bronco sending unit.

As it turned out, the gas gauge was bad, not the sender. I ended up "rebuilding" the sending unit. I spotted a web page on a Bronco website and took the old sender apart, cleaned the contacts and put it back into the car. It seems to work fine now.

GAS GAUGE REPLACEMENT

Having replaced the sender and seeing the same results (with an empty tank, the gauge still read slightly above half a tank) I decided to try a new gauge. I got an Auto Meter 2 inch (actually 2 and a sixteenth gauge to fit a 2" hole). I got mine at Automotive Engineering Performance Centers only because they were close by. It cost $34.99 in May, 2005. It looks similar to the original except that it has a dull aluminum color bezel (ring around it). 

You must specify that the gauge is for a FORD - my box says: "73 ohms empty, 8-12 ohms full For most Fords before 1989 and most Chrysler vehicles."

Well !  The wires and terminals did not match the old, outgoing gauge, so it took some trial and error to get it to work.  Below is what I learned, but use this info ONLY as a guideline in your efforts. I did a lot of trial and error and THINK that below is the final working solution.

TIP:  number the wires with a piece of tape when removing from the old gauge. Below are the numbers that I used.

OLD GAUGE REMOVED

This is how I numbered the wires that were on the old gauge. I didn't number the wires from the light, but just spliced the new light wires on to the old stubs.

NEW GAUGE INSTRUCTION SHEET

Wire # 1 is the source of electric for the gauge.

Wire 2 sends power out to the sending unit # 3 wire has two wires joined together. That is because it is the wire returning from the sending unit, and the second wire is to the ground. In a steel car, I guess the gas tank itself is grounded to the chassis. Wire # 0 is taped over. It has two wires and is not used on the new gauge, so it is just covered up as a pass-through.

In my various mis-wirings, I caused a direct short, since the #3 wire on the original gauge is NOT a ground, even though the gauge says "G". I also pegged the new gauge over on the FULL end (way past full) - because the two positive wires ( #0 and #1) do two different things - one deals with the dash lights and the other with the power for the gauges. As a result of my trials, I lost my dimming capability for the dash lights, and may have burned out that part of the head light switch.

I MAY have been able to repair the old gauge. Between terminals 1 and two is a little electronic component - a resistor or whatever. I didn't remove that to see if Radio Shack etc. could figure out what its purpose was, but I would not be surprised if it had gone bad.

CAUTION: When reinstalling wires keep in mind that the instructions are backwards since you are looking at the back of the gauge. Wire # 1 ends up on the driver's side when the gauge is in the car, etc.