85-F150

is there anything that causes this other than a sending unit? any ideas of what i need to check?

klricks

Engine size? EFI or Carb?
Need more detail as to what exactly you are seeing.
Does the gauge stay on E or F all the time? Erratic or jumping around? etc.

Do both the oil pressure and coolant temp gauges work? If not then there is a problem with the voltage source in the instrument panel. They are all 3 powered by the same source.

If they are good then next thing to do is disconnect the tank connector and use a test light or volt meter to test the sender pin on the connector.

Could be sender most likely or wiring / connectors between the gauge and tank(s) or bad grounding of senders.
If you have dual tanks then the dash switch could be bad as well.

I have more details at the link in my signature.

85-F150

1985 F150, 4 speed, 4.9, Carb, single tank. Everything else works the Temp and voltage both work good. where would i buy a sender at if that is the problem?

Good old Bill

Am likeing the infor put up by kilricks, good stuff, pay attention to him. Further info if you are interested. Remove the connector at the sender, 10 ohms resistance is required for the high reading, 73 ohms is the low reading. Back 40 years ago, we (Ford) used a variable resistor test box to calibrate the gauges, thus the readings provided. Its solid info, not just pulled out of my lower portal.

GhostriderI

Is your oil pressure reading high after the engine is at normal operating temp? I am asking because my fuel gauge quit working and my oil pressure now indicates the top side of the band (AL about 1:30-2:00) it was about 12:00 with the engine at operating temp before the fuel gauge quit. Am getting a 73 ohm and a 22 ohm resistor so I can do the calabration test on both gage circuits. With the 22 ohm to ground when you turn the key on the gauge should point close to straight up (between the RM in normal on the temp gauge and same range on the fuel gauge). with the 73 ohm they should point at about the 10:30 spot on the gauge (around the E on the fuel gauge and the same spot on the oil gauge). these checks will check wiring, IVR [Instrument Voltage Regulater], and gauge at the same time. Connect with power off, turn key to ACC or ON, gauge moves to correct position for resistor. If it does not move check for open in wiring, gauge, or instrument cluster printed circuit. If the gauge moves without the resister connected check wiring for short in the lead to that sender unit. If the gauge moves but is not within range replace the IVR and retest. If it still fails replace gauge.
I bounced between the two test because the only differance st where the resistor is connected, for the oil pressure gauge, or fuel gauge, it is done at there sending unit lead wire and ground.

Hope this will also help you fix you problem