I have a coleman pw0872400.01. Have a major leak at the unloader valve. How do I fix it?

replace tank check valve first if needed unloader valve.

Could be piston O rings, worn cylinder line, worn reed valve-plate assembly, worn discharge check valve, leaking unloader valve. Need info if unloader is leaking or unloader tubing is leaking. The Cheapest and quickest is to remove valve plate assembly and inspect valve plate. Suction side should hold water and discharge valve should hold water placed on bottom of plate.

pressure control valves are non adjustable
They operate to unload the pump when the trigger is released
What can vary pressure is the jet size at the end of the wand
The screw and nut on the valve is only to regulate the stop/start pressure as the trigger is pressed/ released
low pressure at the wand jet can be from low water supply to the pump or pump internal problems

Hi mjschulte815

Here are a few things to check, you may have already checked some of these.

Electricity...Compressors will run best with full 115Vot 15AMP/Or 220V electrical supply from a circuit, over the shortest electrical cord as possible.

Air Leaks..Place your ear close to the compressor and listen for air leaking, if you hear air that is not normal and means you have to locate and repair whatever it is that is leaking.
Check the air unloader valve... The air unloader valve will blown out air when you turned off the compressor, that is normal.
But it should not have air leaking out of it all of the time. If so then it is faulty and in need of repair/replacement.

Valves...If either the intake or exaust valves fail, breaks, or fails to seat, then your compressor will run 24 hours a day and never build up to the correct pressure for shut-off.

Gaskets...Check to see if your gaskets have failed.
You could have a gasket failure between the pistons and you will never know it because it shows no external air leak.
If this situation happens then the air will only cycle between cylinders and never build up the correct air pressure.
One way to check the gasket is remove the air filter, then put your hand over the intake.
Please take time to rate me
Bud
If correct then it will **** you hand against the intake.
If the valve or valves have failed then you will feel the air sucking in and blowing out.

Piston Rings and Cylinder...The piston rings could be stuck,broken, or worn and not allowing the correct pressure to build up in your tank.
A worn cylinder will also contribute to the problem of pressure build-up.

Pressure Switch...Check for air leaks at the pressure switch, it has a rubber diaphram that can fail and leak air out of the system.
Please take time to rate me
Bud

Hi
Sound like your pressure switch is faulty or maybe a faulty motor but:

Here are a few things to check, you may have already checked some of these.

Electricity...Compressors will run best with full 115Vot 15AMP/Or 220V electrical supply from a circuit, over the shortest electrical cord as possible.

Air Leaks..Place your ear close to the compressor and listen for air leaking, if you hear air that is not normal and means you have to locate and repair whatever it is that is leaking.
Check the air unloader valve... The air unloader valve will blown out air when you turned off the compressor, that is normal.
But it should not have air leaking out of it all of the time. If so then it is faulty and in need of repair/replacement.

Valves...If either the intake or exaust valves fail, breaks, or fails to seat, then your compressor will run 24 hours a day and never build up to the correct pressure for shut-off.

Gaskets...Check to see if your gaskets have failed.
You could have a gasket failure between the pistons and you will never know it because it shows no external air leak.
If this situation happens then the air will only cycle between cylinders and never build up the correct air pressure.
One way to check the gasket is remove the air filter, then put your hand over the intake.
If correct then it will **** you hand against the intake.
If the valve or valves have failed then you will feel the air sucking in and blowing out.

Piston Rings and Cylinder...The piston rings could be stuck,broken, or worn and not allowing the correct pressure to build up in your tank.
A worn cylinder will also contribute to the problem of pressure build-up.

Pressure Switch...Check for air leaks at the pressure switch, it has a rubber diaphram that can fail and leak air out of the system.
Please take time to rate me

Coleman PowerMate CT4090410 Operator Parts Manual

This unit uses an loader valve to control pressure, it will unload compressor and idle engine back until the pressure falls below 95 psig and the speeds engine up and loads compressor until cutout pressure is reached. I've linked to manual and the unloader is
Coleman PowerMate CT4090410 Operator Parts Manual Page 18
The item number is 9 and part number is 070-0056.. This part is around $100-$110. Ive repaired this type part on air compressors used on mechanics service trucks ., Depending on your skill level and access to tools and parts, it might be better to purchase a new one.g take time ti read to read and understand manual. Good luck

This is usually a problem with the check valve. The unloader valve on your pressure switch is designed to bleed the pressure off the head of the compressor. With a leaking check valve the pressure isn't relieved from the head and the pump can't turn causing the motor to overload and blow the breakers.

To troubleshoot your problem try the following:

Trace the 1/4" line that connects to the unloader back to the tank. You'll find a fitting there. Remove the lines and then the fitting. Sometimes cleaning that valve will alleviate the problem. If not you need to replace the check valve.

Hope that helps.
-under_psi

I have the same problem. This is the responce for Karcher......

The unloader valve may be sticking, or is dirty. It probably needs to be cleaned and may need to be replaced, it is inexpensive. It gets a lot of use, but extends the life of the pump. The function of the unloader is to allow the machine to run in a bypass mode while the trigger of the gun is closed. First, a lack of high pressure can be caused by: 1. Insufficient water feeding to the unit, so check that the water is turned on all the way and that there are no kinks in the hose. 2. The inlet filter may be clogged. (it will need to be removed and thoroughly cleaned). 3. An internal water leak. 4.Also, low pressure can be caused by worn spray tips. If you have checked the first three with no resolution, the problem is internal and could be as simple as a sticking unloader valve. If you are mechanically inclined, you can clean this valve yourself and greasing the o-rings (use lithium based grease), or take it to a local service center. You do not need to take the pump apar
t. The unloader valve is located under the cover, and is secured with 2 bolts. (Use needle nose pliers to remove the valve) For those units with pressure and volume controls, the unloader is located under the pressure and volume control knobs themselves. Do not take any other bolts off or you will open the pump and lose the pump's oil.

Note: Lithium based grease will prevent future failure of the unloader valve.

Also, check websites such as fixya.com for tips and how-to info particularly on cleaning the unloader valve. Be sure to use lithium grease if you reassemble it.
I am going to check the manuel to see where it's at

Usually, a leak at the pressure switch unloader valve is caused by the checkvalve in the tank. The unloader valve at the pressure switch bleeds out the air from discharge tube after compressor reaches set pressure. This only takes a few seconds. If air continues to leak then air is leaking back into the discharge tube past the tank checkvalve. Follow the air discharge line from the compressor to the brass valve at the tank. The brass valve is the checkvalve that holds the pressure in the tank. There are usually two connections at this valve. One is the unloader tube to the pressure switch. Simple test for leaking checkvalve, with pressure in tank unplug or switch off the compressor and remove the small unloader line at the checkvalve(brass valve) and look/listen for leak. If leaking, remove the checkvalve and examine seat/check for debris keeping the valve slightly open. If it cannot be cleaned, order generic replacement from www.grainger.com. It will cost less than the factory checkvalve. Just pay attention to the thread sizes for easy fit. Good Luck on your repair and email if you have questions.

All electric compressors share a basic design with ac power pressure switch with unloader and checkvalve between the pump and the tank. When the pressure switch powers off, it unloads the compressor by releasing the air in the discharge hose. You will notice a small tire stem pin and a lever to engage it somewhere on the pressure switch. If the compressor stops before reaching set cutoff point, the air pressure remains in the discharge hose not allowing the motor to start, thus the hum you hear. Solution is to check for the proper function of pressure switch /unloader, tank check valve (if check valve leaks air back to compressor it will load motor causing hum) and extra measure check capacitor for at least 90% of rated valve. Finally, do not run this compressor with an extension cord, use more hose instead. enjoy