which wire did you cut into?
The way you are supposed to interface the vaccum locks is by cutting one wire and interfacing it with the keyless entry.
Here is how I do it, using relays to be trigger by the keyless entry.
I also tap into the blue or green wire, but not at the pump, in the passenger wire channel.
Vacuum Type Door Locks
Found mostly on Mercedes Benz vehicles, the movement of the door lock actuators is controlled by a central vacuum pump. The switch changes polarity on a single wire that may rest at power or ground depending on the state of the door locks. You can duplicate this with at least a 2 second pulse. If the alarm or keyless entry you are installing does not have a 2 second or longer duration option for the door lock outputs, do not use this diagram (it will not work unless you incorporate a timer into this circuit).
I always use bosch relays
Check out
http://www.the12volt.com/ for some other great info on wiring things
My aftermarket alarm system allows for a 3 second pulse, or standard pulse, I am not sure if I ever set it to 3 second pulse, and never had an issue with my car locking or unlocking.
I believe there is also a convienience control module under the rear seat on the drivers side of your car you can also work with to interface the keyless entry. this link from our Wika may help you a bit.
http://www.peachparts.com/Wikka/W124Keyless
Feel free to post in with more information.
I have found using relays combined with the aftermarket keyless entry system works best to provide good quality ground or power pulses required for door locks.