Check Gauges/Low Oil Presure

i have a 99 cherokee sport and recently had a problem when i came to a stoplight/sign my check gauges light came on and the oil presure dropped to 0 psi i was told it was the oil sending unit and then told it was the oil pump well those did not fix the problem! i found the problem it was the cam bearings they had so much play that the cam was causing a knock too i replaced cam and bearings and now oil presure at idle is 40 psi just thought you xj owners might like to know