On non-feedback models, the mixture must be set with a CO meter in the exhaust as there is no O2 sensor providing that information. The fuel computer will use the EHA as an enrichment device for starting and for throttle opening via the resistor wiper on the air flow meter, plus usually shuts the fuel off on closed throttle deceleration. It will read 3 mA all the time except with ignition off, closed throttle coast, and during throttle opening events.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!