Late last summer my oil pressure gage quit working . I’m sure oil pressure is good because I drove the car many miles when gage said 0 and it run good .When you turn ignition switch on it jumps and goes back to 0 .I checked the fuses they look good . There is a 2 inch plastic enclosed inline fuse that I have yet to take apart . But I plan to soon . I put a new sending unit in [nothing changed] I checked the wire going to sending unit no power [ I checked it with one of those lights with the alligator ground clamp.] When the car is running should there be power there . When the car is not running with the key on should there power there.