Gas Gauge Sending Unit Repair - 10/17/2015
One of those things that bugs me the most: an intermittent gas gauge. The front tank (and biggest naturally) on this truck had worked on and off (mostly off) ever since I got it. It always read empty for the most part. Though when the tank was low and I would take a corner really quickly, it would climb up and start reading something sometimes. This lead me to believe the wiring was good but for some reason the tank sending unit wasn't working correctly from time to time, like the float was caught or sunk. Reading up on the problem, it seems to be super common among Fords of this vintage. I tried to find another new sending unit, but all came with the pump and the correct sending unit was difficult to nail down. The applications listed a 13 gallon tank, 16.5 gallon tank, front, rear or only tank. This was a 19.5 gallon front tank, which apparently according to the computers everyone has never existed. And I didn't want to pay $175 just to find out the hard way as the electronic pump was included and the one I had was still working. I took a trip and drove the gas tank down to less than 1/4 (which of course during the trip the sending unit started working again) to prepare to drop the tank and investigate.
Filler neck on the bed has to be removed.
External fuel filter, handy reference for the future.
The forward strap bolt. Note how certain items under the body are as clean and fresh as they were brand new and others are rusted up pretty good. This would be the driveshaft. Quality control at Ford didn't specify metal that got painted or needed to survive rust I guess. I've pulled parts out of 40-50 year old cars that lived in this area that look better.
Rear tank strap bolt. Neither of these were any trouble to remove which is a good thing.
All of the fuel lines and electrical lines are here.
Tank drops without a fight. Ford was smart: they made the lines for the tank long enough to reach the ground with the truck level.
The spring clip style fuel fittings are easily removed with the right tool. I did myself a favor and bought the right tool... The plastic filter is the dual tank vent as best I can tell. The other line goes to the rear tank. It slides in a grommet on the tank.
Easy access to everything, this tank sender is held in the way I've seen practically all fuel tanks from the 60's on: metal ring that slides in a circle. I could not for the life of me get the electrical connections off, so rather than stress or break things, I just left them on and worked under the truck.
And out it comes! Float is on the arm on the left. Nice and clean inside the tank.
So here's our problem. The item on the right is the float. It's a brass style float that is brazed together (way to go Ford, using a design GM abandoned in 1968). The float has cracked in 3 or 4 places and retains fuel. This explains why it would occasionally work: I'd let the tank get low and the truck would sit, the fuel would dribble out of the float and it would eventually work fine for a tank or two of gas. Let it stay full and the float would retain fuel and sink. On the left is what GM has been using since the 60's: a nitrophyl float for a quadrajet I had laying on the shelf (I have quite a few spares). They rarely if ever sink because the material is impervious to gas unless it dries out and cracks badly. I plan to make the quadrajet float work in its place.
Just a little bending and some elbow grease and the float is on. The metal line is the correct diameter, and the little bend in the metal is enough to make the float extremely difficult to get on, but with some pliers and care, it goes on and then is bent back and the float now refuses to budge. It's only 3/4" wider than the little brass barrel originally used and doesn't interfere with tank movement (that I've been able to tell). Stick back in the tank and everything works! Easy fix.
While I'm getting dirty, the starter has been acting up. I replace the original factory starter with a brand new AC Delco unit back in January. It worked great for 6 months and then started doing the same thing the 20 year old original did. Solenoid clunks, but doesn't always engage the starter. There's usually 2 reasons why this happens: bad solenoid wire or dirty high current wire to solenoid\starter. I fixed both.
When I put the new starter on, they said to cut the wire and use their splice to crimp the 2 together. I did that, the wires then promptly fell out when I gave a tug. That wasn't good so I put the yellow splice on as seen here and it seemed ok. But when I tugged on it today it yanked out of one side with very little effort and the other side wasn't much better. So much for splices. I soldered the wire this time.
Solenoid wire soldered and heat shrunk to keep the elements out. Let's hope this lasts longer than the previous fix. Insulation on battery post wire is split and reveals green inside...
Not a bad day, only took 2 hours to do everything. The gas gauge worked perfectly without a problem, will give it a few tanks of operation and not sticking or failing to declare success. The starter I then started 12 times. Of the 12, 10 started perfectly with no hesitation. On 2 of them, it hesitated for a second and then started (the first time was the 3rd test, the second was the 8th). Not ready to declare victory just yet, need to watch and let it rain\get humid and drive in some weather to ensure it still starts without issue. With the factory battery cables still in place, it might be time to just replace them as well too.
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Last updated October 17th, 2015