Preliminary Work

Unscrew and remove all spark plugs. → 287020 REMOVING AND INSTALLING SPARK PLUGS
Position cylinder to be tested to ignition TDC and remove tool (dead center finder).
1. 2.1. The dead center finder or "cylinder pipe" consists of a glass tube (inspection glass) with a piston -1- , hose and a rubber cone -2- .
  
  Fig 1: Identifying Dead Centre Finder - "Cylinder Pipe"
  Courtesy of PORSCHE CARS NORTH AMERICA, INC.
2. 2.2. The rubber taper is pressed onto the spark plug hole. The inspection glass is either held by a helper → Tool setup - dead center finder or is secured vertically in a clearly visible position with a magnet.
  
  Fig 2: Setting Tool - Dead Centre Finder
  Courtesy of PORSCHE CARS NORTH AMERICA, INC.
3. 2.3. If the engine is now turned in direction of rotation on the crankshaft, the piston in the inspection glass is pressed up in the compression cycle → Top piston in order to go back down immediately upon reaching the TDC. The piston in the inspection glass stays down in overlapping TDC → Bottom piston .
  
  Fig 3: Identifying Top Piston
  Courtesy of PORSCHE CARS NORTH AMERICA, INC.
  
  Fig 4: Identifying Bottom Piston
  Courtesy of PORSCHE CARS NORTH AMERICA, INC.