Craftsman 2-stage air compressor, model no. 919.167780 ~ Compressor runs but does not build pressure.
by Rob K.
I bought a Craftsman 2-stage air compressor, model no. 919.167780 in May 2002.
I use it regulary and the other day it just continued to run but only built up between 10 -15 PSI compared to the normal 175 PSI.
I got a lot of helpfulu ideas from this website but still have this issue.
I hear no leaks at all and the entire unit is in great shape.
I removed the plastic shroud to gain access to the pump assembly and with my finger could feel only air being sucked into the intake.
Regardless, I removed the high and low pressure head to inspect the reed valve plates. The spring metal for the inlet and outlet plates for both heads were not warped. The high pressure head gasket was also fully intact.
I reassembled the pump and removed the check valve for inspection. The spring loaded seal was not stuck and could be deflected so before threading it back into the tank, I connected the discharge tube and pressure relief tube to it. I turned the air compressor on, could feel air moving through the discharge tube and allowed air to move past the check valve but not sure if it was moving the seal down enough to fill the tank effectively.
The other concern I had was how would I know if the cylinder sleeves and pistons is not the issue. I would hate to purchase the high and low pressure compression ring kit to find out this is not the issue. Any thoughts would be great and I thank you in advance.
Rob, I applaud you on the effort you have put in to try and diagnose the compressor problem.
You have checked everything I would. Here are my thoughts...
~your intake is pulling air and not puffing air when the compressor is cycling, that's good. However, is it pulling air at the same level as before. If you plugged the intake, the compressor should start to overload. If that doesn't happen, then it is pointing to an internal issue.
~with the compressor running you felt air moving down the discharge tube to the check valve assembly. Using something other than your finger, block the discharge port / tube. What happens? If the compressor continues to run without overloading, and you are reasonably sure that the gaskets and valves work well, then to me that really suggests that your pistons are not moving the air well, and that means seals.
Keep us posted, OK?
compressor starts fine then slows to stop
starts fine then slows down and fially stops and then you just hear the motor buzzing
These symptoms suggest a number of things to do with the motor.
First off, make sure that your compressor is plugged directly into a socket, and that socket isn't on a circuit that supplies a bunch of other electrical appliances that are drawing power at the same time. The motor issue could be that it's not getting enough power.
The symptoms also suggest that your motor is seeing increasing load (which is normal as the pressure in the tank increases) but the motor is no longer able to overcome that load and keep running. The buzzing suggests that it's trying to run, but cannot, and if you keep the motor running and buzzing you could burn it out.
If your motor has a run capacitor, this might be at fault.
If there is a mechanical issue in the pump, and that's overloading the motor, that could be the issue.
The least expensive (at least where I am) solution is to find an electric motor rebuild shop and take the compressor to them for a motor and capacitor check. That should tell you if the motor is the cause, or if the pump is.