Why does my diesel car smoke so much when starting ...

Better tune your engine, Change Oils, Spark Plug Polish and Clean your muffler tube.

Diesel engines do not have spark plugs.

you can add a diesel additive i believe it is a stablizer mind just went blank ask for it at your auto parts store just add to your fuel this should fix it good luck

Depending on the color of the smoke that comes out, you could determine what is wrong with your vehicle and why it's starting to smoke excessively in the first place. I found it very useful when my BMW Alpina started to excessively smoke. If its black smoke, it means you have unburned diesel in your engine. If it's blue, then engine oil is being burnt. White colored smoke or steam could also come out, and the only way to determine which is which is by smelling it. White smoke, which smells like unburnt diesel, means that the excessive smoke is probably caused by low engine temperatures. White steam on the other hand, doesn't have any smell and usually means that water is vaporizing.

But since your problem is basically on the fact that your vehicle is smoking excessively, here are some of the things I recommend looking at.

1. Check your air filters. If they are clogged or dirty, insufficient air gets sucked into the system that will allow the diesel to burn properly causing the smoke. Take the filter off then rev up the engine to see what happens. If it still smokes, then it means that the air filter isn't the one causing the problem.
2. The next thing you have to check would be the diesel injectors and engine timing. There is low burn quality of diesel with a dodgy injector, thus causing black smoke. As for the latter, a defect in engine timing would cause a general inefficiency in the system which would in turn create black smoke.
3. If you still can't find the cause, then you would have to ask the help of a diesel mechanic in testing your engine compressions. There would be less compression for complete fuel burning with worn cylinders. Worn valves and/or valve guides can give the same result. Smoke puffing out of the engine crankcase breather pipe could mean that your valve guides are defective.
4. White smoke can be caused by a lot of things, including faulty injector, timing problems (normal cause), low engine compression, and/or a faulty fuel pump.
5. If steam comes out instead of white smoke, then your head gasket is probably faulty or there is a water leak in the combustion system.