First of all it sounds like you have an E65/E66 so you should post it in that forum, but since you've already posted here I start with some questions they will likely ask anyway...
Is your check engine light on? Whether it is or not though, you should always hook up a scanner to see if there are any codes. No scanner? In most states autozone reads them for free.
Cranking without starting could be fuel pump, DME, crank sensor, cam sensor...guessing can be expensive! Not sure about your model but on the M62TUB44 in the E38 there is a schrader valve on the fuel rail for checking pressure which is one way to test the pump. Another way on the E38 is to pop the back seat up and then there is a relay you can pop the cover off and engage it manually and then you can tell if the pump is running, but that might be different on the E65/E66.
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