94 Blazer fuel pump Electrical question

I have a 94 S10 Blazer 4x4 4.3 vin w That I'm having trouble with the fuel pump not working. It started intermittingly working sometimes it would and sometimes it wouldn't. Most of the time it would not start or when you turn the key you wouldn't hear anything from the pump. I don't have a fuel pump test connector like the manual say it should so that's not an option. I tested the relay under the hood(gray wire) and the gray wire only has power for a couple of seconds when you turn the key on. Is this wire suppose to have power all the time? I switched relays thinking that could be it and still no go.When you could hear the fuel pump kick in it sounded real sick. The truck has 150,000 so i'm assuming it needs a fuel pump and was wondering if the gray wire should have power more that a couple of seconds and i've even tried disconnected the fuel line going into the engine and still only has power for a couple of seconds. Where should I go from here? Most would say hook up a pressure gauge but for one I don't have one and second I can't get even a grunt out of the pump when you turn the key on and when you disconnect the fuel line and turn the key on you cannot even use the pump to empty the tank. Any help would be appreciated. Don

The gray wire should have 12 volt power for a 30 second prime when key is first turned on.
Then power shuts off until engine is cranking or when oil pressure comes up on some will feed power to gray wire.
Make sure the orange wire /power feed to relay has good 12 volts on it.
Jumper the gray wire at relay or fuel pump prime connector with a 12 volt fused jumper.
The fuel pump should run if not go to fuel pump wiring plug in and check for power to and threw it and also for ground.
If no fuel pump run them it is drop tank and replace fuel pump.
Also check the pump wiring and wiring harness and plug in real good.

Thank You for the detailed description it is very helpful!!