I have a 1990 f250 that i suspect has a bad fuel pump. It has duel tanks. Is there a main fuel pump that can fail?

check for a resistance in the circuit to the pump
from your description when you have high rpms you will have max charge from the alternator which would increase the voltage available to that pump
bad connections , bad ground (earth)
tyr using a multimeter set on voltage to see the operating voltage available and if it increases with the rpms

You know, sometimes a pump goes bad and needs to be replaced. Have your mechanics test it

Check your control module of your switch and check your big tank is working the fuel pump.

Backfiring is not going to have anything to do with the level of fuel in the tank. You most likely have burned valves or broken valve springs in your engine. I would do a compression test.

the diverter valve that shuts the flow off to fuel tank, and transferes over to other tank is bad. here is a picture of it--1990 f250 valve.

the electric fuel pump is defective in the rear tank, each tank has its own pump

first, is this a diesel? if it is there is a line or oring loose allowing it to **** air--diesels dont like leaks like that and there is a whole procedure for voiding the air from the lines on diesels. next could be the in tank pump and also does it have duel tanks? does the duel tank switch work? running out of fuel with in tank pumps can burn up the pump (the fuel itself provides lubrication and cooling for the pump, gas or diesel) and of course check the filter, running out and refilling could have disturbed trash in the tank

You have duel tanks with a fuel pump in each tank. You also have a fuel pump on the frame rail after the "tank selector". This device only holds a fuel filter that protects the main fuel pump. When you select front or rear tank on the dash, you are selecting which in tank fuel pump will operate. You can check the in tank fuel pump by listening for it to "humm" when the key is turned on..The in tank pumps only feed the main pump and cannot run the engine on their own. Hope this helps

the filter is located approx under the driver on the inside of the frame rail, I think you have plastic fuel line retaining clips in this year, so no tool required. see photo

I would start by checking you switch for the tanks to make sure it is working right and if the front tanks fuel pump does not work after you check the switch I would get a 12 volt electrical test light and see if your getting power to the front fuel pump if your getting power to it I would say you have a bad pump . But some times the pump will run but the diaphragm gets weak in them.