ok that ! light is telling you something is wrong.
it could be anything, like a rich fuel mixture to a bad accelerator pot or poor charging.

does it stay on all the time? or does it go out when you accelerate the engine?
if it stays on then you will need to determine what is causing it to stay on, best way to do this is to hook up and run the diagnostic program and see if it will show you where the fault is originating.
If you do not have the software then you'll need to start checking components like the 02 sensor and alternator output, as for the running rich issue that is most likely a dwell setting that can only be set using the software to set it accurately.

if it goes out when you rev up the engine then i would check the alternator belt, try cleaning the fuel mixer (carb) first.

Thanks, now I have a light on that looks like (!) ???

there is a pressure switch inline with the LP fuel lines, check it and make sure it is not stuck closed.
use ohm meter and read across it, with pressure on it the circuit should be open so the light will not illuminate, then shut off the valve on the LP tank and run engine till it runs out of fuel and engine shuts down, at some point just before that the pressure should drop enough in the lines to close the switch and turn on the light.

if it does not do this then replace the switch