Do you ever service your SPG?

[redacted]

It needs to read zero when it's disconnected and approximate the fill pressure of the tank when it's put on.

And - REALLY IMPORTANT - before it reads zero, your rig still needs to be providing gas.

 

[miketsp]

You mean like this one et al? I hadn't realized that the top screwed on.

At least mine did.
Great photo. Demonstrates what I was trying to describe in words. You can see some of the teeth of the moving quadrant.