My 99 E240 V6 with a new smart key sometimes fires up then dies immediately, I took the car back to the dealer /supplier of key, they had the car for a day, have now supplied a new smart key, but has exibited the same problem, once only so far. So I often use the old key and it seems OK , but I do wonder is there some other problem .

The replacement New smart key has failed again twice today, ie engine fires up then dies immediately, usually on the second attempt the engine will start OK,

The new key has a narrow red verticle window at the end that is inserted into the key slot, the old key had a larger red window, about two thirds of is end size. But I am told by the supplier that this new style one it the only one now available that suits this vehicle

Has anyone experienced this problem, if so what should I do??