It's NOT an ordinary vacuum guage. It's an electronic meter which gets it's signals from a small processor circuit. The circuit compares vehicle speed to the amount of fuel flow and then develops an electrical voltage to drive the meter. The speed value is the same as the tach pulse which drives the speedometer. But I'm sorry that I can't tell you where the sensor is for the fuel flow. I don't have the VDO circuit diagram for this vehicle.

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