based mine only seeming to be not lit it doesn't scare me. it's more of the lights malfunctioning at the top. the bottom hasn't misled me yet as to whats left. but I will say I never let it get below a 1/4 before I fill it back up.

The two main problems are:
-Fuel sender
-Injector size

The fuel sender seems to be pretty spotty, had mine replaced once and it fixed it for awhile but came back now & again. The injector size is causing problems with MPG/Miles to empty/bottom dots. The system is expecting the injectors to run a certain way but with larger injectors they pump more fuel but less often causing the system to think it is running more efficiently. This is not an ECU issues it is another system in the Z which measure MPG/Range and needs to be adjusted so the dots & read outs can properly show.

At this rate, I might have too SMH. :rofl2:

Next time the display messes up, check the Range display. If it matches the gauge (ie, close to zero), it's probably the tank sensor or wiring (a not uncommon problem as mentioned above). Else I suspect a bad gauge, possibly a common ground/supply for the dots.

If you never been inside the tank. It has 2 float sensors. One on each side. They're both a resistor type of sensor. As the float moves up and down. The other end of the arm moves on a resistor grid, changing the voltage signal back to the gauge basically. If one of the floats has absorbed some fuel. It will not float as high. Giving you a low reading. Or if the arm is bent. It might not be going high enough to trigger the last full light on the gauge.

Yeah I have the same problem. Have the f.i. TT and flex fuel. Even before flex fuel and e85, the problem was there.

My worse,i never pumped full tank,but last week,my Country's National Day,petrol is a tad cheaper,pumped full tank,now used 180km,but still no drop in dots....worrying.

In the case of my '11, that last dot can only be "filled in" with slowly pouring the fuel in using a small fuel container. The size of the container is important to control the flow rate; I use a 2-gallon. Don't use a 5-gallon container.

I think you're right. My tank is pretty much full and the last few lights never light up.
http://images.tapatalk-cdn.com/15/09...145b2462c9.jpg

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But I think the range is fairly accurate. I don't have the balls to actually test it tho lol. Always fill it up when it goes under half tank.

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D'oh. I just dawned on me. I should have included it in my earlier post. Also a part of the resistor grid may be dead. Had a '99 Grand Cherokee that had a dead spot in the grid. The fuel gauge would read fine from full to just above a half tank, then quit reading until the fuel level dropped just below a half tank. But when it was in that dead zone. The gauge would read empty. Thinking about how the Z grid could be. The dead zone could be from where it stops reading to full dot.

Sorry to revive an old thread…but there are two fuel sending units in our Zs, correct? One on the passenger side that is a part of the fuel pump assembly, and another on the drivers side that is only a fuel sending unit? I’ve been having a P0300 that’s now turned into a P0305 and my fuel level gauge has just started acting funny. So I’m suspecting my fuel pump hat is broken or something. I was thinking about just buying a new fuel pump assembly and also buying the fuel sending unit for the drivers side just to cover all the bases.

But just to confirm, if I buy a fuel pump assembly it does come with that sides fuel sending unit?

Just buy a new billet fuel pump top hat from CJ Motorsports. You won't have that issue again.

:iagree:

The OEM top hat uses plastic threaded rods that get brittle and break over time. CJM billet top hat is the way to go.

Thanks fellas. But question is more about the fuel sending units. If I buy a fuel pump assembly, it comes with the fuel sending unit for the passenger side, correct? Then I could just buy the fuel sending unit for the drivers side and that would cover both?

I would definitely pick up a billet top hat. Is that a pretty straight forward install on a brand new fuel pump?