Very interesting. According to my understanding of how alarms & keyless entry work in MB's, when splicing into the vacuum pump you do the following:
When using relays (our vacuum system requires two relays), the two green wires (87a + 30) must separate the lock/ unlock wire. This means two cuts. In your photo, I only see one. Perhaps this is your problem. If that wire is not connected to something how will it be able to function??
By the way, what is the exact color of the wire?