The ventilation system vacuum harness, which is connected to the air intake duct, the distributor, and the air intake manifold, provides ventilation to the distributor. This prevents moisture build-up and possible ignition failure. A check valve at the air intake duct connection insures one-way flow through the distributor to the air intake manifold. The ventilation system vacuum harness connects to the air intake duct and the air intake manifold with vacuum fittings. It attaches to the distributor at two places with separately sized connectors. In the case of ignition system failure, check the vacuum harness for proper hook-up and/or kinks. If OK, check the ventilation system for a possible restriction before removing the distributor. Disconnect the vacuum harness at the air intake duct and check for vacuum using a vacuum gauge. The gauge needle should slowly move towards manifold vacuum. If no vacuum is present, replace the vacuum harness.

Important: Failure to connect all hoses of the ventilation system will eventually result in distributor failure.

Once it has been determined that the ventilation system vacuum harness is functioning properly, disconnect the vacuum hose to the air intake duct. Running the engine with manifold vacuum present in the distributor may lead to engine misfire.