I have a problem with fuel shortage or Lowe voltage. coast to lite excel oration.

At the fuel pump, pink with lite blue tracer is voltage.
I looked at the fuel pump relay , there are two lite blue wires with orange tracer. I divide the relay into two sides, load side, has the arm with arrow head, that lite blue wire is voltage, you can see the fuse. The control side of relay is that coil looking symbol, that lite blue wire is ground controlled by computer.

Use a test lite. If two wire connector for fuel injector, one is voltage the other is ground. With some makes and models, the voltage goes hot with key on and the computer supplies the ground. You may need to use a noid lite, see if it will flash, engine cranking. My info is very basic, because I don't know your year--make--model?

When a gas engine back fires and at times loses power at times just before back-firing it can sometimes suggest that the fuel tank's overflow tube, which is also responsible for allowing air to replace the fuel as it burns, otherwise, there would be tremendous suction by the time the tank was emptied. If you are losing power just before producing a back-fire event, the suggestion is, once the fuel reaches a certain level of suction, the engine dies because the suction is preventing the fuel from advancing, then, when the engine finally back-fires, it is because a blast of fuel was just pushed into the engine while it was coasting because of the shortage of air. If there is something you still don't understand, please respond accordingly.

There no switch.
The pink wire at fuel injector is voltage. The other wire is ground, controlled by computer. There is a fuel injector fuse, not only check the fuse, check the fuse circuit for voltage. Use a test lite to check for voltage.
Engine cranking, do you have spark at the spark plugs? Use a gage and check proper fuel pressure.
Any applicable trouble codes?

Coil pack is famous on these cars try another coilpack two types multiplug oval or square

ECU fried ? You could take a multimeter and troubleshoot all power-lines first to make sure there is voltage everywhere to start with / or isolate any shortage/breakage ...

could be in need of a tuneup,or maybe a timing issue. would try the tuneup first...good luck

get the code read and check back. autozone will check it for free. many auto parts store will do it

sounds like your PCM might be bad if it is not supplying correct voltage to fuel injector.

Also, the fuel injector itself may be bad or bad ground.

Does it have throttle body injection on that crown vic?

sounds like there could be voltage shortages in there. check your battery and charging system. use a multimetre to get accurate readings.

check the sensor connections as well. disconnect, clean and reconnect and see if the issue still arrises.