Last summer, my oil pressure gauge was acting up. The second I fire up the engine, the gauge buries itself past 400 kpa. Then after I drive it around and it warms up, I'll stop at a light and the gauge starts bouncing all over the place until I drive off. Every once in a while while I'm stopped, it'll actually work properly and it reads just under 200kpa, but that only lasts for a few seconds before it either pins again or goes back to jumping around.

My guess is that the oil pressure sending unit is at fault here (which I don't know where it is), or maybe there's a bad connection or exposed wire somewhere. But either way, I'd like to get as many pointers as I can so I can get a running start at diagnosing and fixing it when I get it out of storage in a few weeks.

 

Stock gauge or aftermarket? Electric or mechanical gauge?

ASSUMING it is a factory gauge, disconnect the wire at the sender. With the key in the RUN position, the gauge should read zero. Ground the wire to the sender. The gauge should read full scale. If this works, the problem is the sender. If this doesn't work, the problem is the gauge or wiring to it.

 

In this picture, its right in the center. Note, yours might look a little different.