Air compressor won't build up pressure

My air compressor runs and runs and doesn't build up pressure. Does anyone know where I can get a repair manual on what to check and how to repair...or does anyone out there have any suggestions.

Thanks
dave

Sounds like you pulled out the check valve. It closes against tank pressure to isolate the pump from the tank when it shuts off. Your exhaust valve is now probably doing the job of the check valve, i.e. keeping air from flowing back into the pump at shutdown. Sounds like you have enough power in the motor to restart against full tank pressure but it is hard on the motor doing so. There should be a little 1/4" bleed line from the check valve, or at the cylinder head in a Campbell-Hausfeld,usually leading to a needle valve on the side of the pressure switch, to release pressure between it and the pump when the compressor reaches its cut out pressure and stops. By relieving this pressure, the motor and pump get a loadless start, which results in much less amp draw on the motor. Most compressors will not start without this unloading taking place; they will just sit and hum and trip breakers. Your motor will last longer if you re-install a check-valve and blowdown line.