oil pressure

[rlmccook54]

Hi,
I have a 1990 4runner, v6, auto, 4wd, ps, pb, a/c, cruise, pw. 300+ thousand miles.
About a year ago the oil pressure gauge began to register lower than it did. It would register about 1/2 way across the gauge at higher rpms and close to the left side at idle. Then it began to stay almost to the left at idle and only 1/3 at higher rpms. I check the oil once a week anyway but now daily. Oil level always is at full mark. The truck doesn't leak or burn oil. I read somewhere about an external gauge that can measure pressure if attached somewhere right above the oil filter. The gauge costs around $45.
I want to fix this.
What should I do.
Thanks

[fourwd1]

With 300K+ miles on the engine, I don't know that a new gauge is going to fix the problem.
The engine is worn, when is the last time you put a new oil pump on it?

[rlmccook54]

Thanks for getting back. It is the original pump. What is involved in replacing it?

[fourwd1]

A Factory Service Manual has instructions for everything.
If you search you can find one for a 93.

[jetwhine]

rimccook54,

You could also drop the oil pan and make sure the pickup screen is clean. I have seen many of those clogged with high mileage engines.

[sam333]

First make sure you really have a problem . Check the oil pressure with an external gauge( if you took it to a shop that is the first thing they would do). If you do have low oil pressure( compare your #'s with the manual) you could try what others here have suggested , but at 300,000 its very possible that the bearings are so worn that you need a rebuild.