What causes a Diesel engine to rev up then cut out?

Answer 1

I am not 100% sure but as I understand it if some combustible substance (like an oil leak in a car) gets mixed with the air intake then it will cause the engine to rev up even if you cut the fuel intake (as the oil leak is a second, uncontrolled fuel intake). A lot of diesel engine have safety measures to cut the air intake if it over-revs thus stopping both the intake of air and of the second, uncontrolled fuel intake and thus cutting out the engine.

The above answer is derived from reading discussion about the diesel engines on the Deep Water Horizon (2010 BP oil spill) possibly not having such air flaps to cut the air intake (or inoperative ones) as a possible cause for the explosion that sank the drilling rig given that when the well kicked a large amount of natural gas would have been mixed with the air and if it went to the diesel engine would cause it to rev up. If there were no (working) air flaps then it would cause the engine to over-rev to destruction and thus cause the igniting spark. As of writing it is just conjecture as said diesel engine is still at the bottom of the Gulf of Mexico.