2006 suzuki c50, engine acts like it is out of fuel but only 3.1 gallons can be added

SOURCE: fuel gauge fluxuating

there is a device in your tank that has bouyancy that sends a signal to your gauge. Chances are that it has lost its bouyancy

SOURCE: 94 Dakota 3.9 L v6

I had a similar problem only I was lucky enough that my gas gauge started working after it got lower than a 1/2 tank. It ended up being the float inside the tank. I ended up paying around $90 for the fuel float and it started reading the gas level correctly. But after 2 weeks and some severe cold weather, my engine wouldn't recieve any gas, ended up being the fuel pump. In buying the new fuel pump, along came a new float attached. So if your planning on replacing the float, go ahead and replace the whole pump, it will save you time, money, and hassle after its all over with.

SOURCE: gas gauge reads empty but tank acts like it's full

I also have a 04 with a 1.8L. same problem. I took the fuel regulator off. It is a black box behind the rear tire under car. It only has 2 bolts to take off. After that there is a couple of vent hoses from the tank going to this box. Unplug them and 1 electrical connection. The electrical connection and one vent is connected to a T connection on the box that you can unplug by twisting on the T. Take that T off and look inside where you unplugged the hose on this T. There is a spring and a little plunger inside this tube. The plunger gets stuck. I took a little screw driver and some PB blaster and worked that plunger back and forth a couple dozen times and it unfroze. Put it back together gassed up just fine. I did not look but I was told regulator can be replaced for 200$. But a can of blaster is cheaper.

SOURCE: 2001 hyundai sonata 4 cl can't pump fuel into tank @ normal rate

The sending unit in your tank is going bad replace it.

SOURCE: fuel guage stuck at 3/4 tank on my 2004 Chevy

Hi: It Sounds like you Either Have a bad Connection on Your Gauge or the Sending Unit which is in Yout Gas Tank.Your Fuel Pump and Sending Unit Are Located In Gas Tank.Check and Make Sure your Connections are Good and Clean 1st. But it Really Sounds like your Sending unit has Gone Bad.To Replace Sending Unit You'll Have to Drop The Fuel Tank,Empty As Much Fuel as you Can Either Drive till its empty. Holding your Tank Up is 2- Metal Straps with Threaded Bolts and Nuts, Spray with WD-40 And Let It Set awhile Cause Normaly the Are Dirty. Then Take Eiter A Deep Well Socket if it will reach the Nuts,Or Use A Wrench -Remove BOTH NUTS And also at the Filler Tube You'll Probally have a2-3 Screws you'll need to Take Out. Your Tank Should Come on Down.NOTE: Don't PULL the tank out Until you take your Wire Connects Off Remember Which ones Went where. Then Slide Tank out Away From Vehicle, On The Top Of Tank where you remove the wires where thers a Metal Retaining Ring, You'll need to Spray with wd-40 and Remove that Ring,Buy taking a Screw Driver and small Hammer and Tap it out Going Counter Clockwise. After its Off you will be able to Remove the Complete Fuel Pump Assembly. All you'll Need is to Remove Sending Unit.Since Fuel Pump Was Working Right.See if your Auto parts Store has only the Sending unit.if not try Dealership, Hopefully You Won't Have to Replace the Complete Unit. Hopefully this will help you. Please Let Me Know By Voting for me on the Quality of Solutions i've Given you,And Leave a Testamony if You Will. Thanks From The WYOCWBOY