The application is a pressure vessel that uses a solenoid valve to activate the discharge of water.  The valve system is balanced  by the pressure in the system, and the solenoid overcomes a spring force lifting a valve off a seat, discharging the fluid.  The valves seem to buzz loudly when discharging water.  I beleive this could be a coil problem...?? The fluid is still discharged, but the noise is not evident when no water is in the system.  How can i check to see if the coil is working correctly..  It is 110V 50-60hz.  It seems i need more force to lift the armature. 
Measure the current at the valve.  
Measure the voltage across the coil, as close to the coil as you can.
Compare with the rated values.
Buzzing typically comes from a dirty o rworn plunger/sleeve assembly.
No it's a brand new valve.  I'll see if i can get a measure of the voltage across the coil.  Could this be a water hammer thing.  I'm not sure if it occurs in small orifi.  I am discharging through a 3mm orofice.  Around 100ml of fluid at a time.

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