My fuel guage will drop from the reading to empty and the fuel light will come on then it will go back up and continue doing this while driving or sitting still. It seems to get worse the lower the fuel level is. I noticed also that when I filled up last night and then parked nose first in my up hill driveway, my fuel level is now reading 3/4 of a tank! It did come up a little while I drove, but not much. I put about 11 miles on it after I filled up, so I know this is not correct. I was thinking of replacing the fuel pump assembly. Could it be a connection for the sending unit?

 

Also forgot to say........After I park and shut it off I can hear a sound coming from the gas tank the sounds like someone tapping on the tank. a steady thunk...thunk...thunk....I have never stuck around to see how long it lasts.

 

In some vehicles there likea wave reducing devicethat keeps the gas from sloshing around in the tank and giving you wild readings on your gauge. I don't know if our Rams have such a thing as I've never taken the tank off, but if it does, it sounds like it came loose and is moving around in there.

 

does your 98 have the digital odometer. if so, hold in the trip reset button and turn ignition on, and continue to hold the trip button a few more seconds until is says something like CHEK, then let go of it. the instrument cluster will go through a self test, including a gauge test where each gauge will swing up to about 1/4, then 1/2, then max. if your gas gauge passes this test, then its likely a bad sending unit inside the tank, which lives with and i think is part of the fuel pump and filter. unless your lucky and its a loose wire at the connection. to service it you'll need to drop the tank or raise the bed. another dumb idea from dodge.

by the way, after i stop, i hear a little thump thump from the tank. i think its just the gas sloshing back and forth. its quits after a minute or two.

 

Sending unit could be going out, not an uncommon problem for all vehicles

 

Yes this is not the best thing dodge did but, I just droped the tank in my 8.3L V-10 to replace to fuel pump. I with I know more about your 3.9L I know the 5.9L, 8.0L and my 8.3L all have the same pump and everything is one unit pump, filter sening unit and everything is all together. any way if you get the part and have it ready it will only take you a few hours to do this service. it is easyer with a empty tank.

 

It does have a digital odo. I will check that then the connections. It seems like a bad sending unit though and it is all 1 piece. Thanks!