If you remove one injector at a time and plug the hole, you can put a cup under it and check for the spray pattern.
THIS IS VERY DANGEROUS, SO BE CAREFUL!!!! GASOLINE WILL IGNITE!!!
Also, don't put anything in the hole that will get sucked into the motor. It will pull 20" of vacuum or so.
The engine will skip on the cylinder that the injector is out of because of lack of fuel.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS