Is My Lift Pump Bad?


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A lift pump (gear pump) can be the cause of weak or no lift from the hydraulic cylinders. However this isn’t the only component in the system that could cause this issue.

A bad cylinder could cause these symptoms. A good way to check this is to raise your bucket and put your pedal in neutral. If the bucket drops it is likely that a cylinder is the issue.

If the gear pump is causing the problem it is due to internal leakage. Some of the flow is leaking back through the pump to the reservoir. These issues usually are more noticeable at lower engine revolutions per minute (RPM). When running at higher RPMs the problems may appear to have gone away or are at a minimum.

The relief valve cartridge is another item in the system that can cause problems. If the cartridge itself is worn or bad it will usually exhibit similar issues as the gear pump. Problems will be more apparent at lower RPMs.

If RPM is not affecting the problem it could be the adjustment of the relief valve. If the spring has weakened it may not be allowing the pressure to raise as high as it should. Putting a gauge on your auxiliaries is a good way to check the relief valve setting. Rev up your engine, engage your auxiliaries, and see what pressure you get. That pressure is where your relief valve is opening.

Do not adjust the relief valve inward to test if your pump is good. This can result in damage to the gear pump and/or other components in your hydraulic system. When installing a new pump always adjust the relief valve all the way out and adjust it back up to it’s proper setting using a gauge.


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