During a compression test, either all injectors, or all glow plugs are removed during the test. That will allow the fast/easy cranking. On the early OM603, usually the injectors are removed - make sure you use the injector heat shield (seal to prechamber) under the tester or it won't seal properly. And remove the other five, or they will blow up in the air when you start cranking the engine (don't ask how I know this).