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Troubleshooting Trochoid Pumps (Gerotor Pumps)

If you have a trochoid pump that is failing, it's important to take preventative measures to avoid further damage to your machine tool. In this post, we will discuss how to troubleshoot a trochoid pump and prevent pressure failures and leaks. We will also talk about common accessory problems that can occur with trochoid pumps. Before you begin to assess specific issues with the pump’s internal components, you will need to remove the pump from the machine tool or application and inspect it for any damage. If the trochoid pump has accessories such as a filter or relief valve, you can start with those components first.


If you're just looking to increase your pressure and you have a relief valve on your pump, you can adjust the spring inside the valve to increase or decrease pressure.

You may also experience failures with your filter, which can be replaced by opening up the filter assembly and swapping the filter with the same model or one with a different media, which most commonly range from 200 to 60 mesh.


If you notice that your trochoid pump is still not working properly, the next step is to check for external leaks. External leaks can cause the pump to fail. Gaskets, o-rings, and seals regularly become damaged over time and are often the primary issue.

There's two bolts in the back of the trochoid pump that can be removed. This will allow the end cap to come off, or in the case of a fully loaded unit, the whole filter assembly will come off. You can then take apart the middle section, or the “body” of the pump. Inside you’ll find an o-ring on the back face of the internal body and another o-ring on the front face. Both of these o-rings can get worn, often resulting in leakage, and need to be replaced.

Another common place for an external leak is the front shaft seal between the pump and motor. This seal is held in with a snap ring. Once you remove the snap ring, the seal will come out. What a lot of people don't know is that behind the front seal, there’s a little plate that needs to be removed, so that you can find an additional second seal. If the leak is due to seal failure, it is recommended that you replace both seals.


If you are experiencing pressure loss from the pump or if the pump has just stopped turning there's a couple things you can check to determine the cause. With the body of the pump opened up, begin by pulling out the shaft. On some models you will be able to see scoring in the bushing areas which is an indication this has the pump has run dry for an extended period of time, which will eventually lead to pump seizure.

Another possibility could be that the pump is spinning or the shaft is spinning, but you're not generating any pressure. In this case, you will want to check the key that drives the rotor. If this key is broken or sheared, the shaft will just spin freely and will not generate any pressure.

You can also check out the rotor, which is where the pump generates. Over time the gaps in the port wear during rotation and you will experience pressure loss. If you have reached that point, it is probably best to just replace the pump.

Lastly if the motor is spinning but the pump is not turning, you can inspect if the key (also located on the shaft) that is going into the motor is shared. If this key is damaged you will need to resolve that problem to return pressure to the pump.

By following these tips, you can help prevent pressure failures and leaks in your trochoid pump. By regularly inspecting your pump and replacing damaged accessories, you can keep your trochoid pump running smoothly for years to come! For more information, watch our trochoid pump video at the top of the article.

Do you have any tips on how to troubleshoot a trochoid pump? Share them with us at


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