HH56 wrote:
It is except there is a check valve in the junction block at the manifold that connects to that hose. The valve is there to keep a residual supply in the canister to be able to operate the brakes a time or two when engine is off. Not sure what the opening spec is for the valve but I doubt the vacuum reading after the valve would be much different than the reading before it you would get if you checked at the fuel pump hose..