33 gallon verticle, very seldom used, I would call it brand new! Pump won't turn on.

SOURCE: craftsman 33 gallon air comp keeps kicking breaker

There are several conditions that would cause the problem that you have. Worn bearings, weak capacitor, or leaking in-tank checkvalve. Worn bearings would allow armature to drag against the field windings. Easy to check, motor shaft will feel loose in housing and the bearings will be noisy when you turn by hand. Motor capacitors should read to within 95% of uf value printed on side. You must remove at least one lead and short connectors for a moment then read with meter. Repair shops will generally test for free if you do not have a cap. tester. The in-tank check valve will cause undue strain on the motor if it leaks pressure back to pump from tank. Follow air discharge hose to brass valve at tank. Simple test with air in tank remove airline at checkvalve and look/listen or soapy water. Replace if it leaks or remove and clean debris till no leak. If motor strains with no air in tank I would rule-out check valve. One final condition, which is rare, is the flyball switch inside of motor. The motor has a start winding and run winding. Contacts to this internal switch will sometimes fuse in start position and cause your condition, however a motor stuck in this position will make an unusal sound because it cannot switch to run position. (like a car stuck in first gear) If you feel that this could be the problem, remove motor rear cover and sand contacts. Good Luck on your repair and email if you have specific question.

SOURCE: My 33 gallon air compressor will at start build up

Most likely it is the unloader valve. This is inline with the air filltube from compressor to tank. Somestimes the unloader valve is screwed into the tank and air tube is attached to it. This device takes the pressure out of the tube so the compressor can start without the back pressure from in the tank. Other possibility, the start capacitors of the motor. The capacitors must give a kickstart upon startup or the motor will just hum for a couple seconds and overload the breaker. A tempoary solution is to turn off the power to compressor when it reaches 120psi, then allow the pressure to drop to 40 or less, then turn power on and mostlikey compressor will start with a load of 40psi or less. It is a nuisance but it works until you replace the bad part. Goodluck,Macgivor

SOURCE: I have a 33 gallon craftsman compressor model

i think you will find there is nothing wrong with the compressor part of this its all down to a faulty motor
if it cant start up the motor the motor will hum at first then the circuit braker pops out? yes???
check your getting full mains power first as if its trying to run on a very long extenshion lead its not getting the full power to start up, and you will need a much heaver lead,,,if its in a plug on the wall, change the capasitor on the motor,,,this is the part that hold a lot of volts to kick start the motor over when it first trys to start,,if this capasitor has droped in holding its charge there wont be enough volts in it to kick start the motor over,,so the motor starts to hum first trying to start but it dont stand a chance of spinning up
so it keeps pulling more and more amps till the braker pops out,,,watch this capasitor it can realy bite you if you tuch the two ends that are live????
the motor has two windings in it,,a start up winding and a running winding,, if its been humming for some time now it could have damaged the start up winding