Vacuum Advance Angle, Checking

Vacuum advance angle, checking

Work sequence

- connect SIEMENS tester or equivalent (or tach and timing light) according to manufacturer's instructions
- connect vacuum tester between throttle valve housing and vacuum advance unit connection
- set vacuum tester to allow vacuum to pass through
- disconnect plugs from idle stabilizer and connect together
- start engine and adjust idle speed to 900 rpm
- if SIEMENS tester or equivalent is being used, read off indicated advance angle (basic angle)
- if using timing light, flash scale and note advance angle (basic angle)
- increase engine speed until reading on vacuum tester is higher than 240-280 mbar (180-210 mm Hg)
- switch vacuum tester so that tester holds vacuum on side connected to vacuum unit
- let engine continue to run at idle and readjust to 900 rpm if necessary
- reduce vacuum on vacuum tester to 240-280 mbar (180-210 mm Hg) or 90-160 mbar (70-120 mm Hg)
- note advance angles
- determine vacuum advance by subtracting basic advance angle from measured advance angle

Example: last advance angle measured (-) minus basic advance angle (=) vacuum advance

- compare vacuum advance angles with specified values on specification chart
- reconnect vacuum hoses and adjust idle speed
- reconnect idle stabilizer