The system is actually very simple. The air pump feeds air through the change over valve, which is opened by the vacuum provided by the electronic change over valve, then passes through the one-way check valve into the distributor where it flows straight down into bank 1 and into a hose that leads to bank 2. Maybe the distributor is blocked or the bank 2 hose is blocked, disconnected or cracked/leaking.
Looking at your Durametric values and codes, I suspect something else is going on. Hopefully someone can translate.
