Checking the fuel pump is a little more involved. If there is no fuel at the rail then there is a way to remove the fuel pum relay and jumper the terminals to make the pump run. Neither the pump relay or the fuel pump commonly fail on the 850. If there is no pressure at the injector rail then fuel system is probably faulted somewhere but not necessarily the pump. Cam positon sensors do fail. The crank position sensor will shut the engine off it it fails while running. The cam sensor will continue to run until you shut it off and then will not restart. You can check for spark as always by pulling the coil wire off the distributor end and hold it about 1/4 inch from ground. If there is spark and fuel it should run. areful not to crank engine with coil wire not in close proximity to ground.