I Have mastercraft 3 gallon compressor ,

When you say it does nothing do you mean the motor wont come on or the motor comes on and it wont build pressure? if the motor comes on, there are several possibilities:
1. The unloader valve is stuck open
2. The valves in the head are bad
3. The flywheel is loose
If the motor wont come on, the pressure switch is bad (which holds the unloader valve open)
http://www.mastertoolrepair.com/air-compressor-parts-vt6362-p-60727.html

I would say your pressure is the issue . I had a 60 gallon that was doing the same thing and replaced the pressure switch and now its fine

This is caused by a mis-adjusted or faulty pressure switch. You can start by unplugging the compressor, removing the pressure switch cover (probably where your power cord goes into) and turning the adjustment a bit counter-clockwise ( 2 or 3 turns).

Then give it a test run. If it doesn't seem to adjust, replace the pressure switch.

The issue suggests that the head gasket is blown between the two cylinders or the reed valves are not seating or broken. The only other condition that would cause this is a leak. Here are a couple of simple tests. For leak spray soapy water on all connections and fittngs including the pressure regulator and the bottom of the pressure switch while unit is running. Repair as needed. If no leak is found, run compressor untill it reaches 60 or stops increasing and feel for suction at the air filter intake. The best way to check for suction is to remove the air filter and feel for suction at intake port-hole. The suction should be very strong. When valves are leaking it almost feels that the air is blowing out thru intake. If little or no suction, remove head and valveplate and replace parts as needed. Parts are available at www.chpower.com or www.toolpartsdirect.com. Good luck and post again if you have other question.

You suspect this unit as being a two stage because of the unusually high cut off pressure. It is a single stage and the motor really has a difficult task and is being pushed to the limits. to reach this pressure. We usually reset the pressure to lower setting ~~ say around 140. Your pump probably has a leaking intank check valve (brass fitting at tank) or leaking valve plate in pump. Simple tests : with pressure in tank unplug compressor from outlet and listens for air leak around pressure switch. As you unplug the running compressor from outlet you should hear air leaking from pressure switch for just a moment as air is let out of airline from pump to tank. If air leaks out till zero pressure then change the valve. If tank holds pressure then valve probably ok. Next test, with no air in tank and air filter removed, plug in compressor and feel intake port for strong suction. If the valve plate is bad, suction will decrease as pressure neers the 120 mark till the point of feeling that air is actually blowing out of intake. With good valve plate there will be strong suction untill unit reaches set pressure. If valve plate is bad also change the cylinder and piston ring. Good luck with your repair.

If the pressure switch has been changed you will need to reset it if not ,then is the compressor trying to come back on but will not start untill it reaches 0 psi?

try to adjust regulator, screw under red start button.under cover.

When the pressure switch fails the comperssor will overpressure to the point of safety release at about 150 - 160 psi. It sounds as if your compressor is not producing enough pressure to cycle off at 120 and just keeps running. This happens when air is leaking from fittings or worn cylinder / reed valves. Don't worry, with some simple tests we will find the actual problem. I am assuming that your compressor is oilfree type. If there are leaks the compressor may not reach set pressure. I use soapy water on all connections and on the head/headvalve (remove plastic covers to get to all parts that may leak) while compressor is running. Make repairs as necessary. If still low pressure, while compressor is running and has reached max obtainable pressure (in your case 60 lbs), carefully place finger over intake port hole (remove filter). If the compressor is pumping normally but leaking there will be ample suction at intake and cause the compressor to speed-up when intake is obstructed with finger. If you feel plenty of suction and no visible (soapy water) leaks, then the problem is probably the cylinder /ring is not correctly seating /scratched and air is leaking past cylinder. Make sure that the cylinder /piston ring is properly aligned and that the lip on the vinyl ring is up toward the head. On oilfree compressors you can examine the cylinder by pushing the piston all the way up, then look for scratches neer top of cylinder. If scratched, pressure is leaking past cylinder, install cylinder kit. If you do not feel suction but rather air blowing out of the intake, (do this test when tank has reached 60 psi) then the problem is the headvalve plate/reed valves are leaking. The reeds must seal perfectly on their seats and not be bent or have obstruction. Replace as necessary. If reeds or headgasket is leaking the discharge air will be very hot. Only one other thing to check and that is the intank check valve. Easy to check. Run compressor till you have about 50+ lbs in the tank then unplug compressor. Carefully loosen the inlet hose at checkvalve and listen for air leaking out of tank. (check valve is the brass valve at tank) If leaking replace checkvalve. Use caution when removing head to try and save the gaskets. If you have oil type pump, and no air leaks (soapy water test) suspect reed valves/valve plate. Good luck on your repair and email if you have other question.

The pressure switch will trip off when the compressor reaches the rated setting (usually 120 ~150psi). If the compressor keeps running untill the safety pops releasing air (usually about 160psi) then the switch is most likely problem. I use SquareD switch from WWW.Grainger.com. However if the compressor keeps running but never pops the safety and only reaching around 90 to 100psi, then you could have several other issues including: leaking fittings (check with soapy water), worn cylinder and piston (on oilfree compressor examine cylinder from below and look for scratches), leaking valves on oil type compressor. Please email with your finding and any questions Good Luck

Your comperssor is oilless type and suffers from short cylinder / piston life. When the compressor no longer reaches cycle pressure the cylinder / piston should be replaced. These parts are available at www.chpower.com I believe that the part number is wl210300aj. Not expensive, enjoy.