Why won't it start?

Dianoma fault you need to service the dianoma

Lot of time the A/C compressor bearing brake and lock the belt. After the engine shut down the belt melt and stick to the compressor pulley. remove the belt and start the engine shortly. replace the compressor clutch and bearing or sometimes is better to replace the complete compressor.
Good luck

hi Odd.
see if this link helps you out.
Why car won start troubleshooting tips

could possibly be a crank sensor, not sending a signal to allow any power to the ignition

Have you check the fuel pump

Possibly the fuel pump,if the fuel filter is getting dirty it will make the pump work really hard and make noise,I would change the filter.

Make , model , year and engine please, to check for interference engine.

the noise you heard in the rear was the electric fuel pump working but it sounds like you have an electrical issue check your wire harness for areas that wires chaffed on metal and cause break in the electric current some known areas are inbetween the radiator and the transmission down towards the tranny pan also check fuse panel might have a loose fuse

check your glow plugs they may be damaged or dirty

internal noise is hard to tell unless heard by tech however make suere that yo have oil first, sounds like a connecting Rod is broken