Tom fuel pump on 1989 chevy 2500 truck sometimes

Same as fuel pump relay usually passenger side on the firewall back left when looking under the hood

Backfire on acceleration could be caused by a worn lobe on the camshaft especially on a small block Chevy engine. You have to remove the valve covers and check the lift of each push rod. Sometimes it's quite obvious but sometimes it requires close inspection and even measuring the lift.

could be a fuseable link in the wire to the fuel pump or a bad ground to the pump

I would suggest..starting with our fuel lines. If you have an inline fuel filter change it. get a clear one so you can see if your fuel is even making it to that point. Could be plugged fuel line, bad fuel pump, (I think yours should be in the tank) I would start with the simple things first and go from there.

it looks like you changed all the ignition parts. so Yes you got fire......................but you don't have gas. or it would start. check for fuel again. somethings wrong. if you had gas, it would start. i dont think your getting fuel

Have you checked for spark. If it had spark it should have started when you poured fuel in. I'm guessing it might have a bad ignition module.

You didn't mention fuel filter in your list. That would be the first thing to change.

Sounds like you have a power problem. If your not getting power from the battery the your injectors are not going to be pumping fuel. Check your battery

My fathers did the same thing. we soon figured out that the injectors were not making an even mist of fuel they were just dumping the fuel in. we replaced the injectors and the problem was fixed.

Try replaceing the injection module on the side of the injection pump.