Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Hi, my name is***** will be assisting you.
It sounds like the unloader valve inside the pump is stuck or hung and not working properly which will cause this issue.
If you will provide the model, type or spec and serial number I will see if the valve is offered as a replacement part. Sometimes they are not therefore you would have to replace the entire pump assembly in order to fix the issue.