Craftsman 15 gal Air Compressor 3 hp UMC Horizontal k Oil Free Pump - Answered Questions & Fixed issues

Take the shroud off and check the plastic cover on the end of the motor. It has a tendency to crack the two mounting tabs off and then hang loose. When this happens the start and run capacitor switch disengages and will not let the compressor start and run until the switch is in the correct location. Get some longer screws and a flat strap to hold the cover on securely and it will run.

it seems like you might be adjusting a valve before the regulator. the outlet pressure from the compressor vessel should remain celatively constant. if you are adjusting the pressure whilst using the airtool and when you stop the regulator gauges return to/or close to/ the 150 PSI then this also points to you not adjusting the regulator. Some compressors have 2 outlets... one regulated and the other not.

It sounds like a contaminated regulator, possibly due to moisture if you have never drained the tank. If it is a cheap air compressor then the best course of action would be to install another regulator as it is not worth the time to try to rebuild the regulator as most likely it is not a quality part. I would look into Wilkerson or Speedair brand parts to fix your issue.

if less than 1 yr old you ca get a full refund if you are a craftsman club member. you must take it back to the same store where you bought it at and get a manager from the store to help you. it sounds like the head gaskets blew or the rings failed.I just went through the same thing with a different model of craftsman compressor ,so thats how i know what can be done. They will only help you out if the compressor looks unabused in any way.if its oily leave it that way so they can see its an internal failure. good luck.

Just fixed my compressor. It would start ok when the tank was empty but trip the breaker if it tried to start with pressure. Searched and read about weak caps, or problem with check valve or pressure switch leaving pressure in the pump head, etc. Turned out that the black plastic box which holds the 2 start up caps and is attached to the end of the motor with 2 screws had cracked on the bottom. The black box had tilted out enough that the start up caps switch was not engaging. Pushed on the lower part of the box and it started perfectly. Fixed it for the cost of some 2 part epoxy. Maybe not your fail, but definitely worth checking out first.

The regulator will have an arrow cast into the body indicating the direction of air flow.

If all is well where you say it is the next thing I'd check is the condition of the piston & cylinder then the valve plate. On oilless compressors it's common for the ring on the piston to get worn or have peices come off. It may or may not damage the cylinder but it will be able to compress air until the pressure is too high for the leak past the piston to overcome. Also if the valve plate got overly hot the reed valves may warp or break off, again letting the pump compress air only to a point then the internal leak will prevent it from getting high enough for the motor to stop and cool down.

Hi gregtrulu...
Go to the Sears direct website and you can chat with them,email them, or have them phone call you.
You will ask them about the user manual that you want for the 919.164180 compressor you have
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http://www.searspartsdirect.com/partsdirect/contactus.pd

Normally a petcock valve is closed when the handle is PERPENDICULAR to the flow.

Example:

valve
=====----===== (Open)
valve
====='===== (Closed)

Hi dtsorrell...

If your somewhat of a mechanic/electrician then you can by-pass the pressure switch by hooking the color coded motor wires together with the incoming color coded wires from your power cord in the proper order.
Plug it in and then check to see if it blows the breaker again, if it does then it is your motor that is faulty.
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Hi, my name is John. Welcome to FixYa. Will it come on at all? Check the outlet circuit breaker, if it comes on at all, check where the line comes form the pump to the tank, there got to be a leak, you may have to remove it in order to check under it. Check for a reset button next to the wire coming to the switch. Thanks for choosing FixYa...John

There is a check valve that has gone bad,this allows air into the tank,and does not allow the air to go back toward the compressors head.This can also cause the compressor to lock up.

This sounds like the gage is out of calibration. 50 psi sounds about right for this model. I believe 120 psi is max press. and it should pop the safety at 130 psi. Drain the tank, it has a drain at the bottom of the tank. Remove the gage from the fitting. It should read 0 with it out of the system. If it does not read 0 she is out of calibration. I do not believe this gage can be calibrated back to 0 if it is sprung. You will have to find a new one or do the math in your head. If the gage does go back to 0 once removed. Your regulator is bad, you can try to rap it with a hammer handle to see if that will get it back in line. Next step would be to replace the regulator assy. Hope This Helps Fix Ya up.

If you recently replaced the regulator and you have now air leaking any where if the check valve is free and the regluator is good and it would be leaking if it were defective . Then it would have to be the pistion its a dry pump correct .What dose the tank pressure gauge read you should still be able to regulate between the tank and the output gauge even if the pistion were leaking Try disconnecting the regulator and adapting a peice of pipe then a pressure gauge to that and see what the compressor out put is. And look for air leaks these things are loud and sometimes its hard to notice them so feel all around the mechine when its running because unless you have a massive amount of hours or it it shouldn't be a pistion problem

Since the exact model number manual is not available go to Sears and look at the compressors they have on the floor (or in the catalog). Find one that looks like the one you have and note the model number (these devices haven't changed much over the years). order the manual for the one that matches your machine the best.

Turn on the compressor and look for the air leak. It could be a relief valve or a connecting hose or tube. You must locate the leak then see if it is a part that can be replaced.
Gary

If the tank is full (pressurized): Nothing will happen when the switch is turned on. Bleed some air from the tank to see if the motor turns on when the pressure drops.

If the tank is empty or low on pressure: First check the circuit breaker to the outlet the compressor is plugged into. Next, somewhere on the compressor, usually on the motor, there is a circuit breaker. They are usually a small round white or black button that if tripped will stick out about 1/4 inch or more. Push that back in and check to see if your motor runs. The usual reason for these circuit breakers to pop is because the compressor is being run on an extension cord. Rule of thumb for compressors: run longer air lines, NEVER use extension cords. If it is absolutely necessary to run an extension cord it should be 10-guage and no longer than 25 feet.

Most of these are preset to turn off at 125 or 130. Does it go past 60?

probably a bad pressure switch or the wing nut on the bottom of the tank for draining the tank is open

The UMC Series units do not take oil. These units are oil free.