How to Install a Car Vacuum Gauge

by Robert Tomashek
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Monitoring engine vacuum provides useful information whether you are doing DIY diagnosis, monitoring your high-horsepower engine or attempting to hyper-mile. Whether you are installing a gauge in your vehicle or simply using a gauge under the hood, splicing into the correct vacuum line is vital to getting the right readings.

Step 1

With the engine running and the parking brake applied, locate ported engine vacuum. Find a vacuum hose that is attached to the intake manifold and pull it off slowly. If you get a hissing noise from the hose and the engine idle changes, you have found a good vacuum source.

Step 2

Turn the engine off. Remove the same vacuum hose and install about two inches of vacuum hose onto the port. Install the vacuum "T" between the two ends of the vacuum line. If you are using a vacuum gauge for testing you can now install it onto the T-fitting and perform your tests.

Step 3

If you are installing a vacuum gauge inside of the vehicle, mount the gauge according to the manufacturer's instructions. If the gauge needs vacuum, run a vacuum hose from the T-fitting into the vehicle. Locate where the wiring harness enters the firewall, slowly push the vacuum line in through the rubber grommet and route it to the gauge. If the gauge requires an electrical reading from a MAP sensor, then install the sensor as the manufacturer recommends and run the sensor wire into the vehicle in the same manner.

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