Toyota Repair: Toyota Camry 93 oil pump doesnt work, oil pressure sending unit, toyota camry

Question
Hi Ted!  I have a Toyota Camry 93 , 4 cylinder, 120k miles,  auto, just found out that the oil pump doesn't work.  I've openned to cylinder head cover, removed the crankcase to check screen for sludge but the oil look normal.  Sometimes I could start the car  and other time, it won't start. When the car is running, I can hear noise coming out from the timing belt cover. Right now, the engine won't start.  Question is do you think the engine may be clogged by sludge? What about the oil pump? I've heard it doesn't go bad.  Does it worth it to replace it?  Any suggestion would be very appreciated.

Answer
If the oil looks normal and there is no sludge built up then the engine doesn't have this problem, the noise may be coming from the water pump instead.  To check the oil pump remove the oil pressure sending unit and connect a mechanical pressure gauge, this is the best way to find out if there is a problem with theoil pump.