What do I check?
Sounds as if the sending unit in the tank is bad. They are not cheap (on the order of a few hundred bucks if you can get one from Ford) or easy to change. You could hope that it is simply a bad connection between the switch and the sending unit, but it is not likely. Ford fuel sending unit failures are quite common.
Could it be that the float (if there is a float) has a hole and fills with gas? Or could it be a broken wire?
A new Motorcraft fuel sending switch is either $40 or $50 in the aftermarket depending upon the size of the midship tank (17, 18, or 19 gal, I haven't checked yet to see what I have). Unfortunately, replacing it requires removing the tank. I just replaced the rear tank a couple of months ago. Fun with gas.
I have never seen a failed float, or wire for that matter, but have had 8 or
9 failed sending units. I still have one truck with two bad ones, that will go to it's new owner that way, because fixing it is not worth the cost or trouble to me.
The logical solution since there are two tanks is run it untill the tank you have to drop is empty.
Whitelightning
You don't check anything, you buy and install a new fuel level sending unit in the front gas tank, OR learn how to do the math.
If the tank holds 15 gallons, and you get 15 mpg, then your range is 15 x
15, or 225 miles on the front tank. ALWAYS fill that tank and note the odometer reading. In 225 miles, give or take, you will need to switch to the rear tank and make plans to visit the gas station soon.
That's always a possibility -- the float filling with gas and sinking. It could be a borken wire, but my money is on the float or the sending unit.
I have a BMW that had this sort of problem, and the trouble turned out to be a very dirty constact strip on the sending unit. I cleaned the strip with contact cleaner and a business card until the card did not turn black anymore.
In my BMW, all I had to do was take the back seat cushion out and open the tank through the floor of the car. I also have a '95 Bronco, and I had to drop the tank to service the stuff inside. If I recall, the Bronco did not have the capacity to clean the contact strip, but I did not pay close attention to that because my fault was the fuel pump that had died.
No matter what is wrong, you will need to drop the tank to look inside.
Is it easier to pull off the bed than to drop the tank? If I can pull the bed, I don't have to wait to empty the midship tank.
Drive the truck until the tank it empty. Nothing is easier than that.
Not on an old used truck. I don't think you would get all the hardware off in serviceable condition, and would be replacing it. I'm sure it would be a much bigger pain in the ass.
front tank sending unit.
Some wrong replies in there. The sending unit can be purchased separately from the pump assembly and costs about $12.
no.
You don't have to drop it completely to get the sender out. Get the truck up off the ground safely, so you can sit up under it. Then remove the drive shaft, and remove the front tank strap completely, then loosen the rear strap until the tank drops enough to get the lines off and remove it from the tank. There, no draining, and no fuss. I've done dozens of them this way. BE sure to have some compressed air to clean off the area around the sender real good so a bunch of shit doesn't fall in.
The floats are a composite type of material. Nothing to fill.
Back in the olden days of our '65 F100 -- where the gas tank resided in the space behind the seat with the vehicle occupants enjoying the smells of a freshly filled tank -- the float was a brass bulb that commonly got a hole or two eaten into it. But I digress.
The sending unit has failed ...
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.