- Jan 22, 2001
- 2,888
- 107
- 106
... I consider it a success!
<blog>
I decided to try and tackle the fuel sending unit in my 68 Ford XL. It stopped working years ago, and it I'm tired of guessing how much fuel is in it. Originally I was just going to replace it with a 'new' unit. Although they go for around ~$90, so I was hesitant.
Then I came across an ebay store that rebuilds them. You send them in. They fix it, and ship it back. This got me thinking... if they can fix this, maybe I can service the one I have.
15 yrs ago or so I replaced the original tank with a junkyard one out of Georgia since it had started leaking around the seam at the bottom. I coated the inside of the 'new' one with gas tank sealant just to ensure protection against further corrosion. I had to use the original sending unit as the one with the tank was for a newer model Ford.
I had saved the newer one, so I grabbed it so I could examine how it worked. It's really very simple. A float on a rod, that moves a contact along a narrow curved flat piece of plastic which is wrapped in wire. As the level of gas decreases the resistance increases.
Testing this particular unit, I found it was not reading anything. Turns out the 'wire' between the connector and the rheostat is just a flat narrow piece of steel. This had corroded at the ends preventing any current from flowing. This one was not easy to service though as each end was riveted. Oh well, time to drop my tank.
Since I don't drive it that much I like to keep the tank more full than empty. I was pretty sure it was around ¾ full and it was (~18 Gal). If you're not familiar with full size fords of this era, the gas tank is inserted in a space between the rear axle and the trunk. There are two straps that wrap around it and hook into brackets on the bottom of the trunk.
I get the tank loose and plug the filler hole with a can wrapped in a paper shop towel, to cut down on the fumes. The sending unit is in the top rear of the tank. To open it, there's a ring that has to be rotated to release it. Of course they make it so you have to pound on it. I get my rubber mallet and a piece of wood. I don't want to make any sparks. Wood has no effect, just splinters. So I use the tool they don't recommend. A screwdriver. Though, I do coat the tip with electrical tape.
I get the sending unit out without igniting anything and get to testing it. Turns out the rheostat is working okay. There are two issues though. The ground connection to the connector is increasing the resistance by 16ohms (this made 'full' read as ¾ tank). And the metallic float was full of gas (main problem right here). I shined up the back of the rivet on the ground connection and soldered across the body of the unit. For the float, I popped on the synthetic one from the newer unit. There's no way this one can fill with gas. Nice upgrade Ford. (Though the fact that the newer one also had a insulated in-tank cable made me feel a bit uneasy (my old one was a bare steel strap)).
Now repaired, I put it back in, and go back to pounding that ring back.
Note: Pounding on a tank will increase the pressure if you've sealed it. I got a good fountain going.
Once I got the tank back in, I tested the gauge and everything looked good, but for some reason as I was cleaning up, I still smelled gas. I discovered that a epoxy repair I did to fill a pin hole in the seam had come loose when jacking the tank up. Since the old repair had worked so well (~15 yrs) I got some more of the stuff and resealed it.
Done and no explosion! Time for a smoke...
</blog>
<blog>
I decided to try and tackle the fuel sending unit in my 68 Ford XL. It stopped working years ago, and it I'm tired of guessing how much fuel is in it. Originally I was just going to replace it with a 'new' unit. Although they go for around ~$90, so I was hesitant.
Then I came across an ebay store that rebuilds them. You send them in. They fix it, and ship it back. This got me thinking... if they can fix this, maybe I can service the one I have.
15 yrs ago or so I replaced the original tank with a junkyard one out of Georgia since it had started leaking around the seam at the bottom. I coated the inside of the 'new' one with gas tank sealant just to ensure protection against further corrosion. I had to use the original sending unit as the one with the tank was for a newer model Ford.
I had saved the newer one, so I grabbed it so I could examine how it worked. It's really very simple. A float on a rod, that moves a contact along a narrow curved flat piece of plastic which is wrapped in wire. As the level of gas decreases the resistance increases.
Testing this particular unit, I found it was not reading anything. Turns out the 'wire' between the connector and the rheostat is just a flat narrow piece of steel. This had corroded at the ends preventing any current from flowing. This one was not easy to service though as each end was riveted. Oh well, time to drop my tank.
Since I don't drive it that much I like to keep the tank more full than empty. I was pretty sure it was around ¾ full and it was (~18 Gal). If you're not familiar with full size fords of this era, the gas tank is inserted in a space between the rear axle and the trunk. There are two straps that wrap around it and hook into brackets on the bottom of the trunk.
I get the tank loose and plug the filler hole with a can wrapped in a paper shop towel, to cut down on the fumes. The sending unit is in the top rear of the tank. To open it, there's a ring that has to be rotated to release it. Of course they make it so you have to pound on it. I get my rubber mallet and a piece of wood. I don't want to make any sparks. Wood has no effect, just splinters. So I use the tool they don't recommend. A screwdriver. Though, I do coat the tip with electrical tape.
I get the sending unit out without igniting anything and get to testing it. Turns out the rheostat is working okay. There are two issues though. The ground connection to the connector is increasing the resistance by 16ohms (this made 'full' read as ¾ tank). And the metallic float was full of gas (main problem right here). I shined up the back of the rivet on the ground connection and soldered across the body of the unit. For the float, I popped on the synthetic one from the newer unit. There's no way this one can fill with gas. Nice upgrade Ford. (Though the fact that the newer one also had a insulated in-tank cable made me feel a bit uneasy (my old one was a bare steel strap)).
Now repaired, I put it back in, and go back to pounding that ring back.
Note: Pounding on a tank will increase the pressure if you've sealed it. I got a good fountain going.
Once I got the tank back in, I tested the gauge and everything looked good, but for some reason as I was cleaning up, I still smelled gas. I discovered that a epoxy repair I did to fill a pin hole in the seam had come loose when jacking the tank up. Since the old repair had worked so well (~15 yrs) I got some more of the stuff and resealed it.
Done and no explosion! Time for a smoke...
</blog>
"
Facebook
Twitter