Usually, if a pump relief valve is plugged, the engine will load itself down and possibly even stall at idle due to the power consumed by driving the pump. It can also blow out the gasket at the oil filter cover, if the engine is equipped with one. Try plumbing a known good-condition gauge right into the pressure port on the side of the engine. A 0-100 lb. gauge shouldn't peg out if the relief valve is working, and if it does, you definitely need to drop the pan and figure out why the valve is sticking.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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