97 S10 won't start

97 S10 4.3L Has new fuel pump appox. 3 months. Occasonally wouldn't start. Now it won't start. Replaced relay, relay has power, pump has power,
ground is good. Checked pump power direct to 12v and it runs.
Have read oil pressure switch could cause problem. Can't find it, or circiut to check. Any advise? Thanks!

Sending unit at tank working ? Supposedly you can hear it if you get under tank with engine off and key in run position. But I've never heard mine.