I got a 1992 mighty max 2.4 4g64. The most persistent issue I’ve had was turning it on. I have gotten a new ecu and new starter twice. Ecu clicks on with ignition, small buzzing noise when trying to crank, but no crank. Sometimes I can turn it on, on the first crank, sometimes it’ll take multiple tries, and ive had occasions where it’ll take over 15mins to turn it on (with unplugging battery, unplugging ecu, unplugging starter power). I did receive a fuel pump code, and it went away. I wonder if that could be the problem to my solution. I got a brand new fuel pump unopened. My questions are:

How do I diagnose my fuel pump or confirm that’s the issue?

How do properly replace it? (parts needed, precautions, and trails)