What is firing order for 4 cylinder diesel engine?

There's no single standard firing order for a 4-cylinder diesel engine. Unlike gasoline engines which often follow a set pattern (like 1-3-4-2), the firing order in a diesel depends on the specific engine design and crankshaft configuration. It's determined by factors like balancing and minimizing vibrations. You'll need to consult the engine's specific service manual to find its firing order.