Have you happened to losing suction when operating an airless paint sprayer? Don’t hurry to go to the repair store. Before that, here are four reasons you can check and maintain by yourself.
The Working Principle of Airless Paint Sprayer
To better understand why an airless paint sprayer will lose suction, we should start from learning the working principle of airless paint sprayer. Reading from its name, airless refers to a vacuum.
The piston moves down inside the pump cylinder, creating a vacuum. The atmospheric pressure pushes paint from the bucket into the suction tube. Next, the piston moves up and the inlet check valve is closed, the paint is compressed to a high pressure. And then, the pressurized paint pushes the outlet check valve open, and go through the high pressure hose to the spray gun. Finally, the paint is forced through the tiny orifice of the spray tip, and atomizes into a fine and even mist.
Reason 1: Suction Tube& Filter
(1)The suction tube or filter is clogged
The function of the filter is to catch the dried paint skins, debris and other residual in the paint. So the filter is easier to be clogged compared to other parts. When the suction tube or filter is clogged, the vacuum either can’t form or keeps breaking. Therefore, the pump can not be pushed into the suction tube.
(2)Suction tube not immersed or air leak
If the suction tube is put about the paint, the air will be taken into the pump. Another situation is that the suction tube do not connect tight, so the vacuum can not be created. So before starting, the check of suction tube is immersed and well connected is necessary.
Reason 2: Pump&Check Valves
(1) Inlet or Outlet Check Balls are stuck
The check valve depends on the ball to keep the vacuum. There is the possibility that the ball stick to the seat due to the dried paint or grease. To recover suction, just gently tapping the pump housing with a wrench or a rubber hammer.
(2)Packings are worn or damaged
Packings also acts the role of keeping the pump sealed. If they are worn or damaged, the internal seal fails with the packings. If the packings are worn or damaged when working, it is helpful to have a replacement pump to quickly change and shorten the downtime. And you can replace the worn packings when you have spare time. That is the reason why we usually recommend our customer to buy a replacement pump and several repair kits with the machine.
Reason 3: The Prime Valve
(1)The prime valve is on the incorrect position
The valve must be in the “PRIME” position to allow air and paint to cycle back to the bucket. If left in “SPRAY,” the pump cannot purge air and will not prime.
(2)The prime valve is worn or clogged
Internal debris can cause the valve to bypass internally, preventing the pump from building full pressure even when in the prime position.
Reason 4: Operational Errors
(1)Pressure setting is too low
The pump can not drive enough force to draw paint if the pressure do not be set to a suitable level. In this case, slowly adjust the pressure knob and observe whether the pump can suction the paint or not.
(2)Paint is too thick
The thicker the paint is, the more power the pump needs. So, when you find your airless paint sprayer losing suction, you can try to increase the pressure. If the pressure is already in the maximum level, then the paint is not match your airless paint sprayer. The solution is either to thin the paint or change a more powerful machine to handle the paint.
Starting-up Tutorial
We have shot a tutorial on the correct starting of an airless paint sprayer. This video contains the correct operation of the prime valve.
Ways to try to avoid losing Suction
Do the regular cleaning and maintenance not only can great avoid situation of losing suction, but also extend the service life of machine. Here, we list three basic points for you.
(1)Clean after every use
The most common reason of an airless paint sprayer losing suction is the clogged suction system and stuck check ball. So clean after every use can greatly avoid losing suction when working. We have a detailed tutorial about how to clean the airless paint sprayer. What is more, if you will not use your airless paint sprayer for a period of time, better to apply a few drops of lubricating oil to the pump rod.
(2)Inspect and Lubricate the Check Valve
Except for regular cleaning for the check valve to avoid being stuck, apply the lubricate oil to the check valve after cleaning is also important. If the seat or ball is worn, replace it with a new one before it is completely damaged.
(3)Check the suction tube and packings regularly
A worn or damaged O-ring at the pump inlet is one of the most overlooked causes of an airless paint sprayer losing suction. Even a tiny crack, flattened gasket, or loose fitting lets outside air into the intake path, breaking the vacuum the pump needs to draw paint. Once air enters, the sprayer runs but won’t prime. Tighten connections by hand — over-tightening can crush the seal and create a leak. Also confirm the suction strainer stays fully submerged and isn’t resting in settled sediment at the bucket’s bottom. Keep spare O-rings on hand; they’re cheap, take seconds to swap, and often solve priming problems instantly.
Final Thoughts
Daily maintenance and cleaning work is the key to reducing the situation of losing suction and extending the service life of machine. And a high quality machine with wear-resistant core part can help you save time of maintenance. If you need a professional airless paint sprayer, get in touch with us for more!