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Home >> Mercedes Benz >> 1973 >> 280 >> Repair and Diagnosis >> Engine Performance >> Ignition System >> MERCEDES-BENZ 280 & 280C Engine Modification >> Operation >> Ignition Switch-Over

Ignition Switch-Over

Vacuum ignition retard is in effect between 62°F oil temperature and 212°F coolant temperature up to an engine speed of 3200 RPM. Whenever switch-over valve is activated by relay boxes, vacuum ignition retard will be cancelled. Whenever any of the following conditions occur, switch-over valve will be activated: Below 62°F oil temperature, oil temperature switch will close. Above 212°F coolant temperature, coolant temperature switch will close. With engine speeds over 3200 RPM, RPM switch will activate switch-over valve. Whenever transmission is in fourth gear, transmission oil pressure switch will close. When vacuum is between zero and 5.8 in. Hg, vacuum switch will close. Also, when air conditioner is switched on (if equipped), vacuum ignition retard will be eliminated as compressor clutch shares power with switch-over valve.

NOTE: On later production models, ignition change over speed was increased from 3200 RPM to 3400 RPM.
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