98 deville displayed check fuel guage later the display read starting disabled what is the problem

A lot of these vehicles will stop the car when the system senses a major fault, get it checked out.

No issues with the fuel guage that I know of , but you can follow the basic troubleshooting guidelines. Starting with the wiring disconnect at the fuel tank for a bad connector or bad connection. Only other connection would be up to the instrument cluster in the vehicle. Only replaceable items would be the guage or the sending unit in the fuel tank. You can disconnect the return line circuit or connector at the at the gas tank and jump a wire to the ground the that feeds the gauge and see if the guage moves, but don't and i repeat don't hold to long because the guage will go over hard over and could damage the guage. If the guage moved and I would suspect a bad float on the sending unit or a bad sending unit, either case the fuel pump assy would have to come out for repairs.

Are you sure the injectors are spraying if the pressure is zero ?
Have you checked the fuel pressure regulator ?
Are the spark plugs dry ?

The resistor chip in the key may be damaged or the sensor in the ignition may be damaged. You can have the ignition replaced or disable the theft deterent by hard wiring in the proper resistors. Search the cadillac forums for details on how to do this.

chip in the key not reading -
polish up the chip conections with steel wool.
if that does not work it will have to goto the shop for new lock cyclinder and key

yes. the fuel sending unit in the gas tank does need to be replaced

this may be 2 seperate problems, fuel guage issue may be the fuel guage sending unit, the temp guage may be a stuck open thermostat. Have the engine temp checked after driving at least 5 miles, does the gas guage ever move around even a little, if so it is the fuel gauge sending unit in the tank.

you might want to check the ain fuse's.

this is caused by a circuit board failure inside the digital cluster, this cluster can be rebuilt, the only real option on these is a factory repair center, contact your GM dealer for a name and number.

check fuel sensors, could have tripped.