Starting fluid can help start a diesel engine on a cold morning as long as the fluid that is being used is compatible with a diesel engine. Not all starting fluids are suitable for diesel engines, so it is important to check the fluid carefully. Even those fluids that are suitable for diesel engines, should not be used in engines that have glow plugs or preheat systems. In these engines, the starting fluid could pre-ignite, leading to engine damage and potentially injuring you.