1987 ford f-150 fuel pump problem?

I have an old 1987 Ford F-150 with what i believe is an on frame fuel pump that doesn't work, now what led me to believe its the pump is that when i first try to start it, it ran for about 3 seconds then it quit. I then turn the key on and had a friend listen to see if the fuel pump in both tanks turn on and which they did but then he listened for the on frame pump and that didn't turn on. I don't believe its the relay in the engine bay cause wouldn't that send power to all 3 pumps, i haven't check the inertia switch or the fuel filter canister. Could i hook up a voltage meter pump wiring to check to see if its getting power? I almost forgot to mention earlier but before it ran fine, had no problem with anything but then one day its like the pump died right away. Wouldn't a fuel pump give any sign that its going out cause that what it did on my other pickup

I had a 5.0L 1986 F150 with twin tanks and for a long time it didn't seem to want to go over 3500 RPM. At some point I think my dealer replace that 3rd pump on the frame and no difference. Then one day I drove from IL to northern WI and my gas gage stayed on full. I thought oh well, I have another tank. But when I switched tanks, the gas gage went all the way down (sucked gas from wrong tank), and still would not start. So maybe you have some problem with the valve between the twin tanks.

Yes you can check power at the pump but there's only power there while you're cranking the engine over or for the first few seconds when you turn the key on so it's best to just check it while you're cranking the engine over. You said in the beginning that it starts and then it dies that could be the computer not keeping the fuel pump on for some reason. Start with checking the power thats the best place to start.