GA-7 Cougar Pressure System Issue

[hish747]

This may be a little specific but it's POA so I thought I'd give it a shot. The left vacuum pump failed on my Cougar, with the classic sheared off gear. After replacement, the red failure bullseye on the gauge is cleared, gyros spin up correctly and instruments display normal behavior. However, with only the left engine running, the gauge shows 0 inches of mercury. I'm wondering if anyone experienced this on a Cougar or other twin and if so, what the most likely culprit would be. Regulator? Manifold?
Thanks,
Hish

 

[aftCG]

The instruments operate correctly with only the left engine running, or on both?
Seems like something was not connected back up.

 

[Bell206]

However, with only the left engine running, the gauge shows 0 inches of mercury.

Some dual vacuum systems have check valve(s) that will isolate one system from the other. Its quite possible one valve is stuck after the failure or needs to be reset.

 

[Dan Thomas]

Yup. There's a dual check valve that takes the vacuum from both pumps and has one outlet to the instruments. It might have a chunk of carbon from the failed pump blocking its diaphragm closed.