Compressor start fine if tank is empty, pump to certain pressure and stop. when i use air and need to start again motor try to start but dont have a strenght to move compressor and trip breaker, what can be wrong with it.

check and test capacitor

No water = no pressure. The pump fills the tank with water putting pressure against the bladder inside. Start the pump until it shuts off. Check your tank pressure. Set the tank pressure to 2psi lower than the cut-off pressure of your pumps own cut-off pressure. A tank is used to give water pressure long enough for the pump to start and build it's own pressure. When you stop using water, the pump refills the tank. Ready for the next time you turn on the faucet.

Your tank check valve is stuck/broke. It's on the tank end of the line from the pump to the tank. It is supposed to close when the pump stops to keep air in the tank and let the system bleed pressure out of the pump so the motor can start when there is pressure in the tank. The part you need is CAC-437-2 and is available through searspartsdirect.com.

if its belt driven ,unplug it(safety first)remove the belt and try to turn the pump by hand.if the pump turn plug it back without the belt. and try it .if the motor doesnt run.check the contacts on your pressure switch.if they are ok and try again.if not you need a new motor.if the motor ,the pressure switch contacts,and the pump are fine.put the belt back back on bleed your tank to zero with an air gun and try to run it.if it work well till it cuts of check if your bleeder release air.you might have pressure stuck in your pump.the compressor needs to release pressure for a soft start.hope this help!

The motor will run hot/overload if wrong size or too long cord is used. Also if pressure is set too high (most set at 125 ~ 135 at shut-off). In-tank checkvalve will also have effect on motor by loading the compressor at start-up. Easy test. Run compessor till you have over 100lbs in tank then unplug from power. At this point try to turn the motor /pump by hand, it should turn rather/very easily (this test is hard to do if the motor /pump is completely enclosed, you need to be able to turn the pump even if by truning the fan blade). If it does not turn easily let all the air pressure out of tank and then try to turn by hand. If it turns easily with tank empty try one more test. Run compessor till the pressure switch turns it off. Then unplug machine and turn compessor again by hand, should be easy. If not easy then unloader / checkvalve not working. The checkvalve could be leaking air back from the tank loading the pump. Replace parts as needed.

Your tank valve is stuck open. The valve is on tank where the tube from the air pump goes into the tank. It allows air into the tank but not back out the same way. When the pump stops you hear a short burst of air leaking out that releases the pressure on the piston in the cylinder. If the tank valve sticks open, the pressure in the cylinders is more than the motor can overcome to restart and the breaker pops open so the motor won't burn itself up. The valves are relatively easy to get and easier to replace.

there is a valve under the regulator, at switch off pressure the valve must blow of the air between cilinder and checkvalve after stop running.. when checkvalve is not closed it keeps blowing.

The start valve gives your motor a running start before the motor begins to load as the pressure increases from an empty tank. The motor strain is more profound when there is pressure in the tank. If you plug the valve, the motor will instantly encounter a heavy load because it has to force air into a partially filled tank. This extra load without the valve will shorten the life of the capacitors and motor windings. There could be two problems with your unit that can revealed by test. What actually closes the valve is a certain volume of air produced by the compressor. If the compressor is not pumping to full efficiency or there are leaks in the discharge hose the valve will not close. Or the valve is faulty. With an empty tank, plug the valve and run compressor and test airline for leaks with soapy water. If no leaks, empty tank of air and restart compressor and take note of the amount of time it takes to fill the tanks to shut off. If it takes an unusually long time to fill, then the compressor probably has valve problems causing low air volume. If the compressor fills to shut off in a short time frame as compared to a similar model then replace the valve. Leaking valves in the head will also cause the pump and discharge tube to run very hot. Parts are available at www.toolpartsdirect.com Good luck with your repair.

Check the reset button on the motor to see if it tripped. The motor may be overheating. Some motors have an internal breaker and they have to cool off before they restart. Also check the pressure switch. Move the switch back and forth ( on and off ) and listen for a click. If it doesn't click with low to no air pressure then the switch is bad.

Assuming that the motor is factory matched to pump, it should be powerful enough to turn the pump. Most problems with motors are related to pressure switch and/or capacitor. The pressure switch could have burned contacts causing low amps to reach the motor. The capacitor should test at least 90% of rated value printed on capacitor. Some volt meters have capacitor check setting. Also this motor at 5 hp must draw lots of amps. The outlet should be rated at least 20 amps and plug the compressor directly into oulet without an extension cord. \
Secondary problem is the in-tank check valve. The check valve should hold in tank pressure without leaking back to the head of the pump. If check valve leaks, replace it with any brand of same thread size. enjoy