i have a 1992 ford ranger pickup truck, and the gas gauge keeps failing to work ,
 

what to do next? ok . i have changed the the sending unit module and the gas pump/ reg/ valve and all that goes in the tank.. as soon as i did these changes the gas gauge worked properly for about 2 months. one day after stoping to fll the tank it started, showing a empty tank agian.. now sometimes the gauge will work and sometimes not.. ive checked all the wiring and all is good any help out there? also i should add the engines size ., 2.3 4clyinder with 8 sparkplugs i bought this truck brand new and is a 1 owner

It sounds like your new sending unit is defective. It may not be making good contact. It has to keep good contact while being able to move freely up and down. This could have been bent on install or was just a bad part to begin with. The gage it self rarely fails. By your comments we can eliminate that and the wires. Also did the fuel pump come with the sender and float as a unit or separate. Most fuel pumps come with a decent warranty. If you don't have the receipt the auto parts stores have a database of sales. I assume you work on your own truck so just pull your unit out and get it replaced. If you don't have a ride, buy a new one and tell the counter person your bringing the bad one back for warranty. That way if they give you a hassle you can work it out before you hand over your cash. If you need further help on anything else hit me up here:
http://painintheexhaust.blogspot.com There is an ask question section.

Best guess: you have an intermittent open or short circuit in the wiring. More than likely, it's near the sending unit wire. If it's the slip on type, remove it, clean it, and make sure the small strip of metal inside the plug isn't cracked or bent. If it's the screw on type, check the connection at the sending unit again. If both are OK, then I would guess it's in the harness. You may have pulled on a wire when you changed the unit, closing the circuit, but over time, the vehicles vibration caused the circuit to open again. The same applies if it's a short circuit. The vehicles vibration causes it to open or close once in a while, making the gauge work sometimes, and stop working sometimes, as you explained.

I guess the only thing you haven't tried is replacing the gage itself. 4 cylinder with 8 spark plugs! Guess Ford was up to something.

Re: i have a 1992 ford ranger pickup truck, and the gas gauge keeps failing to work ,
 

Found out the reason for 8 spark plugs was because Ford was in the early stages of developing the now-standard EGR system. I guess what they didn't realize was they could route any exhaust gas back into the intake, instead of trying to burn off any leftover gas during the exhaust stroke.

Re: i have a 1992 ford ranger pickup truck, and the gas gauge keeps failing to work ,
 

You do know this thread is over 2 years old right? :)