Diesel engine knock

Those copper and gold flakes in the oil is actually brass most likely from the crank and or rod bearings. It's hard to say what is actually making the noise without opening the engine up. It sounds like the engine is blown & needs replaced instead of trying to chase down a knocking sound just do the job right from the beginning or you will wast a lot of time & money

Spray some starter fluid into the throttle body to see if it will start. If it does, you have a fuel problem.

comment on petrol or diesel
in any case have a compression test done to check for mechanical failure

Be sure all safety items are in their proper position. Brake set, blade disengaged, etc. This will prevent engine from starting. This is the best place to start troubleshooting.

You mean it will crank but not start ? Do you have normal compression, spark and fuel pressure ?
If the timing belt broke you won't have compression on all cylinders.

Generally three things can turn the light on. First is the sending unit itself if it's going bad. Next is an obstruction of the pump pickup screen (usually hard carbon deposits). Third is worn engine bearings (usually rod bearings). Best way to find the problem is to have someone put a mechanical pressure gauge on the engine and read the actual pressure. If it's low you need to go into the engine to determine why. if it's normal, replace the sending unit. Senders aren't terribly expensive and you could just buy one and replace the one you have, providing the engine isn't tapping or knocking.

check fuel pump pressure

Sound like a bad ground wire going from engine to firewall...

Try the electrical iginition switch, and the "candybar" on the front of the distributor.

this engine fuel pump prassurae low. it fuel pump celan. Your problem sovel