Complex sentence: This booby trap was also used to destroy vehicles--the modified grenade was placed in the fuel tank, the rubber band would be eaten away by the chemical action of the fuel, releasing the safety lever and detonating the grenade.
Split into simpler sentences: This booby trap was also used to destroy vehicles with the modified grenade was placed in the fuel tank. The device would be triggered when the rubber band would be eaten away by the chemical action of the fuel, releasing the safety lever and detonating the grenade.