Lesson 12
How Diesels Differ
See how a diesel lights its fuel, why its filter needs long runs, and what to do if you put in the wrong fuel.
Ignition without a spark
Squeeze air hard and it gets hot; you can feel it in the barrel of a bicycle pump. A diesel squeezes its air much harder than a petrol engine does, until it is hot enough for fuel sprayed into it to ignite on its own. No spark plug is needed. That is compression ignition.
On a cold morning, the cold metal of the cylinders soaks up some of that heat, so diesels have glow plugs, small electric heaters, to help them start. On many diesels a coil-shaped light on the dashboard shows while they warm up; wait for it to go out before you start the engine.