If it is in fact connected on both ends, but still does not register on the gauge, there are only a few possibilities.
1. You have no oil pressure.....
2. The gauge is faulty..
or...and my mostest favorite one of all...
3. The plastic line has kinked, or melted/fused together under the dash...usually right where it passes thru the firewall, or shortly after that point. I've seen that more than once.....
Best way to confirm #3 is to install a temporary gauge right on the engine. If pressure there, then blow some air into the plastic line and check the gauge. If nothing, then disconnect AT the gauge and air it up. If the gauge works then, you know the cheesy plastic line if fubared.

FUBAR: Of all the military acronyms, my most favorite!  Other than BOHICA, of course...

Is removing the fuse links a common practice?

(quote with images removed-aapple)

|UPDATED|6/4/2014 10:03:41 AM (AZT)|/UPDATED|

 Yeah...it actually is, tho it's not recommended. Those fuse links are there for a reason....it keeps from burning the car to the ground if something shorts out that would normally just pop a fuse. Fuse links are installed in certain areas of the wiring to protect as much of the wiring as possible, which is why those are down by the starter....they protect pretty much the entire vehicle harness. There are other fuse links in other areas, such as behind the distributor(for the A/C system, and/or power windows, if equipped), but the ones there by the starter usually power the headlights, and interior stuff.....just depends on which circuit they are on.
You can get replacement fuse links at most parts houses, if you find that yours have been cut out. It's possible that bulge there is replacement fuse links....need to unravel the tape and see....just be sure to disconnect the battery first.