sound on engine

have a 90 Cherokee with 240,000 miles i am getting a knock on the engine don't now were it is coming from, engine still has a lot of power it sounds like a diesel engine any chance of knowing what this cud be

If it's rymthmic and changes with engine rpm, could be a rod bearing.

Start it up and let it warm up. Raise the hood and listen around. Does it come from the top (valve cover)? Does it sound like it coming from lower down?

An old trick it to take a long screwdriver and put the tip on a spot on the motor. Then put your ear to the other end (the handle). You'll hear the engine noises transmitted up the screwdriver. Then move the screwdriver around to other spots and listen. When you hear the noise loudest, you're in the right area.

Or you can go to a autoparts store and get a mechanics stethoscope.

These engines are known for strange noises when they get high mileage.
These engines, up until 2001 or so had a defective piston design which allows for excessive piston slap (clearance), yet will still run fine.
Sometimes a worn oil pump produces low oil pressure and can make the bearings noisy.

I believe the noise is coming from the bottom and when you rev the engine the noise follows the engines rpm. will this decrees whatever life i have on my engine if it happens to be a bearing or should i not worry about it. And is there a reason for my oil gauge to be all the way max out?

How bad is the knock chico? Is it horribly loud or just a tapping sound? If it's not too loud, IMO is no cause for concern.

If you want to isolate the exact rod, just pull one spark plug wire at a time while it's running. When the knocking goes away, you have the deviant rod. Chances are greater it'll be #1 or #6 rod (the farthest from the pump...last to get pressure....first to wipe out)

The oil pressure guage thing is unrelated. Just go you your local chrysler dealer and get an oil pressure sending unit ($30 canadian) and replace your faulty one, adjacent to your distributor; one little wire attached to it.

If it turns out to not be a rod check the torque converter to flex plate bolts. If they are loose it sounds a lot like a bad rod bearing.