When parked for like 10/12 hrs,it needs a minute or two of cranking to start agn

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My touareg is 2.5 r5, once started it cranks in about 2/3 secs the whole day, but if parked for like 10/12 hrs, whether morning/night, winters/summers.... it needs a minute or two of painful cranking. I have consulted a few local mechanics who say one of the injectors is faulty and the whole cylinder head needs to be replaced and a few blame the fuel pump... if found common plz help me out with this riddle, thanks in advance