Usually is the input impedance of the load 10 times higher than the input impedance of the sender. So the sender's ohms is one tenth of the load.
0 Ohms empty, 90 Ohms full.
Check out www.fordification.com/fuel-sending-units.htm I think you will find your answer there.
2o ohms to 200 ohms is what i'm getting on my 87 model
About 2 when full and around 75 empty
Check the glow plugs (ohms) and wiring for shorts
full 10 ohmss empty 80 ohms
135 ohms new, and will function properly down to 114 ohms. The chart in the '86-'87 book shows: Empty=110 ohms +/- 7 ohms Full=3 ohms +/- 2 ohms 1/2 full= 32.5 ohms +/- 4 ohms
In the up position, it should be 20 ohms. In the down position, resistance should be 220 ohms.
With a multimeter. The easy way is to unscrew, disconnect and remove the sending unit from the tank for testing. Once removed, connect the multimeter to the chassis of the sending unit and the isolated stud that was wired to the fuel a gauge. Depending on where the sending unit's arm is positioned different resistance values will result.
Full position (up) - 7 ohms Half tank (middle) - 33 ohms Empty position (down) - 95 ohms
78-84.8 ohms empty 4.3-5.8 Full
More than likely it will be the armature on the fuel gage sending unit in the tank/tanks. Pull the sending unit(s) out and test the resistance in the two posts going to the armature. Should be 165 +- 5 ohms full and around 10 +-5 ohms empty. (must manually move the float while testing resistance) If it isn't within factory specifications, sending unit is bad. If it is, then there is a wiring issue up to the gauge.