If you hear air leaking out of the small centrifugal unloader valve at the front of the pump and/or if the tank doesn't hold air after it shuts off then your check valve is probably defective. This is the valve that's typically threaded into your main tank inlet that keeps the pressure in the tanks. It's probably back-feeding into the line and out through this valve, also putting pressure on the pump head, making it difficult to start and stay running (in a lot of cases).

Try this test to be sure:

1)Let your unit pump up. 2)Turn it off. 3)Find the supply line from the pump to the tank. 4)Remove the supply line from the pump head. 5)If you hear air coming from the tank you have a defective check valve.

You can click on the below link to view a technical document as well as a short video:
www.mastertoolrepair.com/how-to-test-check-valve-p-22524.html

It would also probably be a good idea to replace the unloader valve (elbow) on your pump that's leaking, it may simply be defective. The spring inside could have lost its tension or there could be debris inside.

Let me know what you find and we'll go from there.

- MTR

Glad to hear it! You're right, always verify. I'm just glad you're able to get it up and running again.

- MTR