Engine: Testing and Inspection
Determining the operating cycle of cylinder 1For some tasks, it is necessary to be familiar with the position of the piston in the cylinder (ignition TDC, overlapping TDC).
Caution: Risk of damaging the timing drive mechanism!
^ Forces from the valve can cause the timing chain to jump over or to tilt.
^ Never twist the crankshaft against the direction of rotation.
^ Remove and install the chain tensioner only in overlapping TDC.
^ Never twist the crankshaft when the chain tensioner is removed.
^ Never twist the camshafts when the chain tensioner is removed.
^ Never apply forces across the camshafts in the timing drive mechanism.
^ Always counter the sprocket wheels when performing assembly work on them.
^ Ignition is off, ignition key is removed.
Note:
^ All spark plugs (except for those on cylinder 3) must be removed to ensure that the relevant dead center can be found more easily.
^ The torque support bracket can remain in place.
1. Remove spark plugs (except those on cylinder 3).
Compression cycle for cylinder 1 (ignition TDC)
1. Find ignition TDC of cylinder 1. To do this, insert the ignition rod module of the first cylinder into the corresponding opening in the valve cover and press in firmly.
2. Twist the crankshaft in the direction of motion until the ignition rod module comes out again with an audible plop.
3. Then twist the crankshaft until the fixing bore on the crankshaft belt pulley is aligned with the bore in the timing case cover. The engine is now located in the ignition TDC of cylinder 1.
Note: If the crankshaft is then turned through 180°, the piston in cylinder 1 will be located in the lower dead center. The emission cycle then follows.
Intake cycle (overlapping TDC)
1. Find overlapping TDC of cylinder 1. To do this, insert the ignition rod module of the first cylinder into the corresponding opening in the valve cover and press in firmly.
2. Twist the crankshaft in the direction of rotation until the ignition rod module comes out again with an audible plop.
3. Then twist the crankshaft until the fixing bore on the crankshaft belt pulley is aligned with the bore in the timing case cover. The engine is now located in the ignition TDC of cylinder 1.
4. Remove the marking mandrel if necessary and twist the crankshaft through 360° in the direction of motion. The engine is now located in the overlapping TDC of cylinder 1.
Note: If the crankshaft is then turned through 180°, the piston in cylinder 1 will be located in the lower dead center. The compression cycle then follows.