I've just been having a problem with my car too. When I first started driving it, the oil pressure was about 45psi on the gauge when driving, but recently it struggles to get on the gauge. I was concerned at first, but the oil light wasn't lit, and the engine sounded sweet. I got home and checked everything, and found that the wire was a slightly loose fit on the oil pressure transmitter, so the vibration of the engine running was causing a poor (resistive) connection, so it was reading a value, but reading low. I cleaned and tightened the spade, and now everything is good. The trouble with oil pressure gauges is that they can cause paranoia; The gauge reads zero, therefore the oil pressure must be zero. Not necessarily true. I checked my pressure gauge by shorting the oil pressure transmitter wire to earth, you should get full scale reading on the oil pressure gauge. That proves the wiring to the gauge. If that's working, then maybe the sender's not. These engines don't tend to have huge amounts of oil sloshing around the top end anyway, so be wary of using that as a benchmark. If the oil light goes out, then there must be some pressure. I recently changed the oil on mine, and with my other cars, I always disconnected the coil to stop it starting, and crank it til the oil light goes out before allowing the engine to start. I couldn't do this with my car, I couldn't get any pressure on the starter alone. I bit the bullet & started it, because I knew it was ok before, & I'd only drained the oil & changed the filter, and when it started, it sounded fine, and the light went out & the gauge started reading properly only after the engine was running. I'm not saying that your car's the same, but just saying don't always trust the oil pressure gauge without doing other tests. Maybe you could remove the sender & connect a mechanic's oil pressure gauge to test your pressure hydraulically instead of electrically?
