Gas level gauge shows full all the time?

[camaro]

Hi there, car is a ZJ Jeep Grand Cherokee 4.0, 1998, with the "tank under the floor" option - handy because it means no loss of boot space or spare, but a pain because it doesn't hold a lot of petrol any more!
Anyway, amongst other problems (bit of a stutter at about ik rpm, severe loss of power on gas, but runs fine on petrol), the gauge shows full all the time. It's an AG Autogas system from 2002, switch/gauge looks like this, except the line of LEDs is curved - .
I know they aren't the most accurate of things, but this just keeps all the green lights lit. I can tell it to turn on to gas from cold, and the red LED will flash until the engine is warm enough, then it'll switch to gas fine - but keep telling me it's full until it runs out!
Is this likely to be something I can remedy with a new switch/gauge? Or level sensor - where does that go, and how does it work - a float sensor for liquid level, or pressure sensor - is it easy enough to replace for a pretty accomplished DIY mechanic?

I'd just like to get a vague idea of when my Jeep might decide to run out of gas when I'm in the fast lane...

[richard_ha]

The car I bought does exactly the same. As you mentioned they are never any good anyway. I just reset the trip counter and know that I can get 250 miles on one tanks, that's the easiest way!

Was the system fitted recently? If so take it back and get them to fix it. If the gauge isn't reading correctly it might be indicative of a larger problem (tank/valve rotation).

[camaro]

It's an AGAutogas kit - fitted in 2002, so no youngster! I'm doing the same as you at the minute, keeping an eye on the trip counter - and a jerry can of petrol in the boot!