Racor RK 19669 RK19669 Vacuum Gauge, -30 to 0 Hg Bottom Mount

This is the same gauge used on the RK19671 T-handle.- Racor is pleased to announce the following improvements to the Fuel Pressure and Restriction Gauge Improvements include: Stainless Steel case and face increased from 2.0 inches to 2.5 inches diameter for easier reading. The improved cases feature a pressure relief valve to adjust to ambient barometric pressure changes. Gauges with acrylic lenses upgraded to polycarbonate. Needle stops replaced with internal locking Mechanism to prevent damage due to an accidental overpressure. Internal sealing at the fitting, lens, and pressure relief valve reduces the likelihood of internal contamination by splashing fluids.

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.