Compressor shuts off before reaching max pressure

The pressure regulator on an air compressor is designed to let the pump motor run until the pressure in the tanks reaches their safe level. While you are using the air the pressure drops in the tanks until it reaches the level where the pressure switch turns the motor on again and refills the tanks to their rated level. The pressure where these two things happen is usually with in ten psi above or below the rated levels because few regulators are so precise and are affected by temperature that they turn and off exactly at the rated pressures. If a pressure regulator is damaged or broken it is possible for the tank to either reach unsafe high levels or not turn on when the pressure drops to where it should restart the motor. If you are in doubt, have the regulator checked or replaced as overpressured tanks are very dangerous.

If your compressor is oil-less type, most likely pressure is leaking past piston ring. To verify, remove cover to expose bottom of cylinder (unplug compressor and let out all air). With flashlight, examine the upper-most part of the cylinder (turn motor by hand till piston is at top of stroke). If top of cylinder is scratched, then pressure is leaking past.
For many years now, stores are in a race to have more HP and PSI to attract customers. Customer is really the loser because components used to make the units can not handle the higher pressure. Normally small 115v compressors are set to cut out at 125psi and larger two stage units will cut out at 160psi. Small compressor set to 200psi makes for short lived compressor. Could be compared to driving your car at 100mph all day every day. Longest life is attained when unit is being used at about 60 to 75 % of capacity.
To allow your compressor to reach cutout pressure and keep working for a while, lower cutout to 120psi (pressure switch may be adjustable). To restore to 200psi, replace cylinder/ ring.
If your compressor is oil type, suspect leaking reed valves.

A piston in any engine should be around 100 psi I would guess. A Chevy 350 used to be around 150 psi. An air compressor that only pumps enough air to reach 20psi is obviously too low on compression. Nailers and the like need 80 or more psi. The intake valves may be shot, the unloader might be stuck or piston rings are worn.

Hi, my name is John. Welcome to FixYa. Look on the pressure switch and see what the max. is. I have some notes here I will have to locate them and I will post them here if you still having problems, but it sounds like you need to replace the pressure switch. Thanks for choosing FixYa...John

Model Number: SS3J5.5GH-WB Manufacturer: Ingersoll Rand Tank Size: 8 Gallons Engine Engine HP: 5.5 HP Engine Type: Honda GX 160 Fuel Tank: .8 Gallon Pump CFM @ 90 PSI: 11.8 Max Pressure: 135 PSI Certification: UL/CSA/ASME Overview Dimensions: 43" x 18" x 26" Product Weight: 175 lbs
this can be a reference.

Does it shut off at 25 psi or just keep running and never build more pressure than that? Also, did this come on gradually or suddenly? Also, was it being used regularly when it happened or had it been sitting for a while?

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

Check the check valve. They are usually where the air line goes into the air tank. On some they are a teflon washer that starts to leak. There is a spring that closes the valve after each pulse of air is pushed into the tank.

If your pump is shutting off before it reaches it's max psi. then you need to adjust you switch. Under the black case there are two adjustment screws. One is the high\low adjustment, the other is high pressure cut off.
The first will change when the pump turns on and off for your low psi setting and the high setting simultaneously.
The second will allow you to raise or lower just the high setting. There should be a diagram under the black cap to show which is which. Adjust the high side only and just a 1\4 turn then run the compressor and see if that takes care of the high setting.