Next job I tackled was to see why my fuel gauge was reading past “Full” when the ignition was turned on, indicating a possible open circuit.
I used some 30 ohm resistors in parallel to get different readings.
I’d read that the gauge is supposed to read empty to full in the range of 0 to 30 ohms. The photos in order show:
- open circuit
- 30 ohms
- 15 ohms
- 7.5 ohms
So, with the gauge working, I removed the fuel sender which had no gasket installed and one of the 5 screws was snapped off - I later drilled this out to replace the screw.
As there was still fuel in the tank, I quickly made up a temporary paper gasket and used the fuel sender from my FC wagon to stop fumes coming out.
As a comparison, the FB sedan sender is on the left and the FC wagon on the right, which has a shorter lever due to a shallower tank.
I drilled out the two copper rivets, separated the two main parts, and found a peened post had snapped off, resulting in a few loose and broken bits inside.
There was a broken brass shim type piece that kept me pondering for days what it’s purpose was. I started another thread to see if anyone knew what it was, but no luck. So I removed the FC sender, which also wasn’t working, and pulled it apart to find out - I had to make a blanking plate for the fuel tank as I had no more senders to use
The blanking plate
I worked out that this little broken bit provided a “short” for the resistor. Without it, the resistance would be somewhere in the range of 8 to 12 ohms, or a quarter to a third of a tank when the tank was empty. This is because the copper contact on the other half of the unit (this runs along the resistor as the level changes) touches the resistor about half an inch from the positive terminal post, where it would read almost zero ohms.
The trick here was to make this “shim” the correct length. As you can’t see where the contact sits when the unit is closed, it’s a bit of guess work.
The FC unit with the arrows showing the shim with a couple of tabs sticking out either side of the resistor and Bakelite insulator.
The new bit made from brass shim - the broken one alongside. The new one doesn’t have the tabs and I’m not sure what effect this may have down the track.
To put all the bits back together, I first cleaned everything then drilled a hole about 1/4” deep into the positive post from inside the unit - just big enough to fit some copper wire a bit larger than 2mm diameter.
I forgot to take shots to show what I did next so, in case anyone’s interested, I’ve quickly made a mock up of what I did using a similar sized screw and some scrap sheet metal
The drilled screw
The screw was then heated with a gas torch on low heat, and the drilled hole was filled with solder and the copper put inside the hole while the solder was still molten.
I then fit all the pieces (scrap sheet metal used in this mock up) on the copper wire and then cut and squared off the copper wire, leaving it proud by about 1mm
Next, I used a centre punch to slightly spread the end of the copper wire before peening it with a ball pein hammer
This worked well, but when I heated up the terminal post, I burnt the insulator between the post and sender body, so I made a new one out of some 3mm Teflon sheet I had.
I put it all together using 2 brass screws and nuts until I get the copper rivets that should be here some time this year on the slow boat from China. I looked around but couldn’t find any locally.
Then for testing, showing empty, half and full
The mounting screws were all different and washers damaged so I’ll grab a new set from Rares next time I’m up that way. The gasket in their kit appears to be rubber and I think the originals were cork - anyone know if one is better than the other?
Feeling pretty pleased with the result, I thought I’d tackle the FC sender. The problem here was in the other half of the unit. The “springy shim thingy” that goes from the contactor to the body to complete the circuit had snapped into 3 pieces. The arrows show the two bits that should be joined and the second photo shows the bit that goes between.
I cut the remaining bits of shim off and, after a good clean to reveal shiny copper, I put dobs of solder on the two terminals, then cut some brass shim to solder on and replace the original shim.
It’s a little rough but works, and only time will tell how long it’ll last. It tested at 11 to 41 ohms instead of 0 to 30, so I’ll have to bend the wire lever to fine tune it, but that can wait until I get back on the FC...........
Well, the end of another epic but hope someone finds it useful or interesting. I had fun doing it.
Cheers,
John
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Looks like I'll have to replace the spring posts though, as Rob mentioned. When I do that, I'll check all the other flogged out bits and fix them on both sides. Then it'll be better than a bought one 
