Testing; Dynamic Basic Setting; Measuring The Spark-Advance Angle - Bosch ETZ 309 Bedienungsanleitung

3. Testing

3.1 Dynamic Basic Setting

When working with ignition distributors fitted
with vacuum timing-control detach the vacu-
um hose if so specified (see test specification
sheets).
l Connect the ignition-point stroboscopic
timing light
Let the engine operate at cranking speed
unless some other speed is specified by the
engine manufacturer (see test specification
sheets).
Direct the flashing light at the rotating timing
mark (on the flywheel or pulley). This rotating
mark must line up with the fixed timing mark.
1 Advanced ignition (before top dead center, TDC)
2 Retarded ignition (after TDC)
3 Basic setting (TDC)
l Correction
Release the clamping or fastening screw at
the ignition distributor.
At a suitable engine speed turn the ignition
distributor until the rotating timing mark rea-
ches the position specified in the test specifi-
cation sheet. Then retighten the distributor
clamping or fastening screw.
3.2 Measuring the
Spark-Advance Angle
A prerequisite for an accurate measurement
of the spark-advance angle is that the basic
setting of the ignition timing mark is correct
(see Section 3.1 above).
l Rotating Graduated Disc
In engines which have a graduated disc in-
stead of the rotating mark (e. g., Daimler-Benz
engines) the graduated disc moves in the
direction opposite the direction of rotation
when the spark is advanced.
The scale reading opposite the fixed mark
gives the spark-advance angle directly in an-
gular degrees.
The check of the ignition point at a higher
engine speed, for example 3,000 rev/min and
31°, specified by the engine manufacturer, is
a test of the spark-advance angle.
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