u.s. patent no. 10,995,713

The rapid primer was invented, designed and produced by a marine diesel mechanic to make primary fuel filter services easier and cleaner. The rapid primer works by creating a vacuum inside the filter housing when the tool is pressed against the housing and the pump is pumped. The low pressure within the housing allows fuel to flow from the tank and thereby fills the housing which eliminates the need to fill the housing with a separate jug of fuel. 

After replacing the fuel filter element, or servicing the filter housing bowl, the housing will need fuel added before the lid could be reinstalled.

1. Place a used o-ring inside the appropriate sized groove of The Rapid Primer Tool.
2. Open the fuel valve only for the housing to be filled.  If the filter housing is part of a dual filter setup, make sure that the valve is not set to "on" for both housings, otherwise the tool will suck air from the other housing.
3. Press and hold the Rapid Primer firmly on top of the open fuel filter housing and begin pumping. Continue pumping while monitoring the fuel level inside the housing.
4. When the fuel level reaches the top of the filter housing, stop pumping and remove the tool. Note: Although the rapid primer is equipped with an overflow reservoir,  it is good practice to avoid drawing fuel up into the pump.
5. The fuel level will most likely recede a bit, after reaching the top of the housing , as the fuel flows to the center of the element and the element absorbs fuel.
6. Place the tool back on top of of the housing and pump slowly to raise the level back up. This will likely take a few cycles of pumping and waiting until the fuel level stabilizes at the top.
7. If the fuel level continues to drop after repeated attempts to top the housing off, it is likely that the anti-drainback mechanism (located within the diffuser of the filter housing) is not functioning properly  and needs to be serviced.
8. After the fuel level has stabilized near the top of the filter housing, reinstall the lid on the housing and repeat the procedure for the remaining housings.

Cleaning The Pump

• Before  storing the tool, make sure to empty out any fuel that may have been drawn into the pump and overflow reservoir.
• Tilt the tool backward toward the pump handle with the overflow  reservoir angled down and pump it a few times.
• Now tilt the tool forward with the reservoir angled downward and allow any fuel in the discharge tube to drain into the reservoir. 
• Pour the fuel out of the reservoir into the waste bucket.
• Repeat the process until all of the fuel is drained from the pump and reservoir.