lam5

I have a 92 sc300. About 3 times a month while i'm doing about 40 to 55 mph the engine will die. The car has to sit for hours to days at a time for it to restart. I thought that it could be the fuel pump relay, but i really think it could be the cam or crankshaft sensor. Is there a way to test the sensors before being standed again? If so where are they located?