99 marquis got spark got fuel starts with starting fluid relay seems fine switched

Check fuel pump relay . Do you know what a relay is ? Go to your tube . Fuel Pump Electrical Test Relay and Fuse check Advance Auto Parts

The fuel pump relay is in the powerbox on the drivers side of the car. It can be in a relay trio which is hung behind the powerbox and has a slide out access to the relays inside or it can be inside the big powerbox. Usually the cover has the relay name and position embedded in the plastic.

If the engine is cranking over, it is not a problem in the starting circuit-forget the starter or relay-but possibly a problem in the ignition circuit. Since you can hear the pump turn on, first thing to check is the ignition-check for spark at one of the spark plug wire ends. You need to see a blue, snapping spark to know the ignition circuit is working. If you do have spark, check fuel pressure and check injector circuit.
Have someone help you check for spark if you haven't done it before. Someone will have to help you anyway, by cranking the engine over when checking for spark.

you missed the fuel pressure regulator. ti keeps the fuel running in the fuel rail

When you say the fuel pump relay is good did you test for power to the relay circuit ?

you will need to check fuel pressure and spark, you have the car there in front of you. Its not going to be the fuel filter. Did you check the fuel pump inertia switch in the trunk?

fuel shutoff switch is actually a fuel pump relay in the relay box under the hood, but it is not unusual for a fuel pump to work on and off before it finally dies. but it is a good idea to check the relay first.

try swapping it with the horn relay (if the horn works). pay attention to the direction the relay is in. on GM's, it's possible to put them in backward or even miss the connectors completely.

you also want to check for proper power and ground in the relay socket.

try the coil pack check it for spark

The 99 GMC, when it acts up, check whether it has fuel and/or spark. It could be related to fuel pressure, available electrical power, ignition component/s.

well the first part of your question i was all ready to tell you to put a new fuel pump in, now not so sure, there is a relay for fuel pump, can you hear pump cycle and relay click? relay under hood you will have to listen close they don't run long maybe a couple secounds, if you don't relay bad. if you do pump could be bad, do fuel pressure test pump could be weak. don't think sunroof and turn signals are related, but stranger things have happend.