Hello All,
So, at idle, my oil pressure gauge drops to ZERO! when I rev up a bit, the needle comes off the peg, but still reads fairly low. It's been doing this for several years, It was vandalized when I bought it for 500 bucks but with very little work, I was able to get it running great. It's a 1974 FJ40 with the origional engine. (I think a F?) There is an oil pressure regulator located on the outside of the engine which is adjustable (I read that). It sounds like it's a pressure relief device to relieve excessive oil pressure back to the pan resevior. Is there a chance this regulator is maladjusted and can be adjusted to increase the relief pressure which should raise the operating oil pressure or is it more likely the oil pump is getting worn out and needs repair? The engine runs at 180 deg. F fairly constantly and I watch it closely doe to the oil pressure issue.

Any guidance or advice for a path forward to resolve this issue would be fantastic.

Thanks in Advance....Lance

My old 69 did the exact same thing...after adjusting the regulator and putting in a new pump...I just had super high pressure at cruise. The regulator doesn't really do anything ad idle...it just works when the engine is at its max oil pressure setting.
My guess would be bearings...either cam or crank and rod....or both. I even tried doing the bottom end in the truck...and it helped for a little while. Mine was worn cam bearings. Do it like I did...drive it til it pops!!

Thanks Killerpee,
I adjusted the regulator yesterday, it was backed way out and I screwed it all the way in, amazingly, the oil pressure gauge is showing some pressure now and when I rev up it goes to just below normal (halfway point). I suspect you are right however, probably bearings so I think I'll do like you did..Run her till she pops! Thanks for the quick response...Lanhavy