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Page 6
SKU 03343
Operation (continued)
Testing Centrifugal Advance
1. With the timing light still connected and the vacuum line still not attached, speed the
engine up slowly and watch the timing mark.
2. The timing mark should remain stationary until the engine reaches the manufacturer’s
specified speed. See FIGURE 3. Then the timing mark should move steadily, without jerking.
3. If the mark stays stationary or moves erratically, the Centrifugal Advance (or automatic
advances) should be serviced by an authorized service technician.
Testing Vacuum Advance
1. The vacuum line must be connected to the distributor for this test.
2. Idle the engine (no more than 800 rpms) and attach the vacuum line to the distributor.
Note: If it is difficult to do, decrease the engine speed.
3. Aim the Timing Light and note the position of the timing mark.
4. Disconnect the vacuum line.
5. If the timing mark stays still, the trouble could be a plugged line or a leaky diaphram, or a
frozen distributor plate. See an authorized service technician if the timing mark doesn’t move.
Checking Distributor Cam Wear
1. This test is done after the timing has been set and the timing light lines up with the
reference pointer for cylinder number 1.
2. Connect the Timing Light to the wire directly opposite (180 degrees) from the number 1
cylinder on the distributor cap. See FIGURE 4.
3. Start the engine and aim the Timing Light towards the timing mark. The reading should be
the same as when the Timing Light was hooked up to the number 1 cylinder. If not, the
probable cause is a worn out distributor cam or bent distributor shaft. Contact an authorized
service technician.
FIGURE 4
8 Cylinder 6 Cylinder
4 Cylinder
No. 1
Cylinder
No. 1
Cylinder
Opposite
Cylinder
No. 1
Cylinder
Opposite
Cylinder
Opposite
Cylinder
The opposite cylinder is always opposite the number 1 cylinder on the distributor cap.
Maintenance
1. Keep the Timing Light clean by wiping it with a dry, lint free cloth.
2. Before and after each use, clean any dirt, grease, or debris off of the clamps.
Do not use the Timing Light if any of the wires are frayed or torn.