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FAQ Spotlight: Using RK19669 and RK19668 Vacuum Gauges

Where do I connect the Racor RK19669 or RK19668 Vacuum Gauges, and how do I use it?


First, the gauge belongs on the vacuum side (outlet) of the filter, and before any downstream pumps. Tap into an unused outlet port on the filter head, or connect to a T-fitting located at the filter housing outlet. Use pipe dope sparingly instead of pipe tape. The gauge allows a dirty filter element vacuum limit to be set, and mechanically records the highest vacuum seen; even after engine is shut off. A routine visual gauge check takes the guesswork out of filter element change schedules.

Using the Gauge:

There are three needles on the gauge face. The first one (black) is the vacuum indicator. When the engine is on, it moves and shows higher vacuum as the filter plugs with contaminants. This black needle returns to zero when the engine is off. When the filter element is new and the engine is on, it will typically read about 2 inches Hg.

The second needle (thin red) is a "follower", and is manually set when the element is new by turning the center knob clockwise until it rests on the black indicator needle. When the engine is on, any increase in vacuum moves the indicator needle and the red follower by the same amount. When the engine is off, the indicator needle returns to zero, but the red follower stays at the highest vacuum reached.

The third needle (thick red) is set manually to the maximum tolerated vacuum (minus about 1.5 inch Hg) required by the engine manufacturer. The vacuum limit can also be determined by artificially restricting the fuel flow until the engine cannot maintain full power at full throttle. In use, when the thin red follower reaches the setting of the service needle, the element should be changed promptly. After the change, the follower is once again manually returned to sit on top of the black indicator needle.

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