Why should starting fluids not be used on engines equipped with glow plugs?

When considering the use of starting fluids on engines with glow plugs, the primary concern is the potential for an explosion. Glow plugs can reach high temperatures as they are designed to heat the combustion chamber for improved ignition. If starting fluids, which are typically highly flammable, are introduced when the glow plugs are hot, the mixture can ignite too rapidly, leading to an explosive reaction rather than a controlled combustion process.

The risk of an explosive ignition is particularly pronounced in a confined combustion chamber, where the mixture of fuel vapor and air can combust with dramatically increased force. This uncontrolled ignition can not only damage the engine components but also pose serious safety hazards. Thus, engines equipped with glow plugs should avoid the use of starting fluids to prevent such dangerous situations.

Other options, while they may have some relevance in different engine contexts, do not capture the immediate and significant risk posed to safety and the engine when using starting fluids with hot glow plugs.