the fuel pump
When you turn the ignition to ACC or On you'll hear a buzzing or whirring sound. If this sound isn't heard you'll have to drop the fuel tank and replace it. Get it done by a proffesional.
Turn the key to the on position without starting the engine, listen closely or have a helper listen to the rear driver's side, where the fuel tank is. When the key is turned then fuel pump comes on, making a slight whirring sound. If there is no sound at all or something more than a slight whirring sound, it's probably about time to replace it. Also, if it takes a long time cranking to turn over the pump may not be building pressure properly.
Your fuel sending unit is malfunctioning.
Try checking to see if your fuel pump comes on. To do this all you have to do is remove your gas cap and it's easier if you have somebody there to help you with the next step. Get in the truck and turn the key to the on position not running, then see if the other person can hear a whirring sound in where you removed the gas cap. If you do not hear a whirring sound then it's time for a new fuel pump, and if it is you have problems elsewhere.
If the fuel pump is working it will presssurize itself. Any air in the system will dissipate through the fuel pressure regulator and the injectors. You should hear a whirring sound when the fuel pump comes on at engine startup. If you don't you don't have any fuel pressure. Check the relay and the fuse.
Normally only a very minor whir.
Probably the fuel filter is clogged and there was never anything wrong with the pump to begin with. Can you hear the pump making a whirring sound when you turn on the ignition. If so, the pump is all right and it is the fuel filter that is clogged up.
If the old one is malfunctioning, yes.
If it is malfunctioning it can affect fuel mileage.
The yellow fuel dispenser is an indication that your fuel is running low. The red battery is an indication your charging system is malfunctioning. The red water symbol is an indication your cooling system is malfunctioning.
first have an assistant turn the ignition switch to the on position and listen for the whirring sound from fump pump, indicating pump is operating. If fuel pressure is in question you can install a tee fitting between fuel filter and fuel line and purchase a fuel pressure gauge to connect to the tee fitting. fuel pressure should be at 43psi with key on engine off, and 34 to 36psi with engine idling.