Hydraulic pumps operate on the principle of liquid going from a high-pressure area to a low-pressure area. Hydraulic pumps cannot function if there is not enough liquid in the pipes, as they will not be able to create enough pressure. This means that if your hydraulic pump is low on liquid, for whatever reason, you need to prime it by putting more liquid in the pump.
Fill a bucket or container with the liquid you need.
Pour the liquid into the pipes.
Add liquid as needed until your pump is working. Be aware that this may take a long time and can be very tiring.
Install a T-clamp on one of your pipes.This is a clamp that allows you to attach a third pipe or valve.
Install an elbow on the T-clamp. An elbow is a pipe that angles at 90 degrees.
Install a valve on the elbow.
Open the vent on the shutoff valve so that air escapes as you put liquid in. If you don't do this, the air will have nowhere to go and you won't be able to prime the pump.
Pour the liquid into the valve. If you have a water pump, you can just put your hose in it. Oil can also be poured into the valve. Priming this way saves you from having to make multiple trips to the end of the pump to prime it.