How to adjust suction - see picture attached:
Order is important so first adjust Max, then Min and lastly Rate.
Remove cylinder and replace with a vacuum gauge or manometer. Keep in mind that the cheap vacuum gauges that come on brake bleeder pumps are not very accurate - see:
Anyone using water lift to measure/regulate vacuum?
#1 Adjust Max suction
Rate valve full open
Min suction valve full closed
Max suction full closed
With pump turned on, gauge should read max suction of pump.
Open Max suction valve very slightly and observe gauge. It will not take much opening of this valve to lower suction. This is what has been referred to as a "controlled leak".
Label the valve with tape if necessary so you know which valve is Max suction.
#2 Adjust Min suction
Rate valve full open
Min suction valve full closed
Max suction valve adjusted in step #1
With pump turned on, gauge should read the adjusted max suction of pump (step #1).
Open Min suction valve to full open (big leak) and gauge should fall to Zero. Carefully close the min suction valve (smaller leak) just slightly and observe gauge - it should rise off Zero. Set to desired minimum suction. Label valve with tape - this is the valve you will put your finger over to start and stop a cycle.
#3 Adjust Rate
Rate valve full open
Min suction valve adjusted in step #2
Max suction valve adjusted in step #1
Have a timer (seconds) visible
This step is trial and error and depends on the volume of the cylinder used. Remove the vacuum gauge and replace with cylinder. Enter the cylinder as you normally do. With pump running, watch the timer, listen to the pump and put your finger over the end of the Min suction valve (this is when the labels come in handy). Observe how long it takes for the pump to reach the adjusted maximum suction and release your finger. Repeat the cycle a few times to confirm the time in seconds. Now adjust the Rate Valve to full closed then open just slightly. This should slow down the rate of air leaving or entering the cylinder. Repeat the cycle, observe the timer and adjust the Rate valve to achieve the desired time.
Hope this helps - please report your results!
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