Volkswagen Golf Mk1 Service and Repair Manuals - Workshop and Auto Repair

To reduce the amount of CO and HC in the exhaust gas, air is routed throught an air pump behind the exhaust valves into the cylinder head. At high engine speeds, part of the air is routed into the open air via the diverter valve. In overrun, air is passed via the anti-backfire valve into the intake ducts to prevent backfire.

Chenking air pump

• ‒ → Pull hose off check valve -arrow-.
• ‒ Run engine; air must emerge at end of hose.

The pump is to be checked if no air emerges:

• ‒ Pull off hose at pump.
• ‒ Run engine and check that air is flowing out of the air pump.
• ‒ Renew air pump if there is no flow of air.

Checking diverter valve

• ‒ Allow engine to idle.
• ‒ When outlet of diverter valve is closed off with finger, only a slight pressure should build up.
  If a considerable pressure builds up, the valve must be renewed.

Checking anti-backfire valve

• ‒ → Pull hose off -valve -arrow-.
• ‒ Briefly increase engine speed by opening the throttle valve.
• ‒ Abruptly close throttle valve.
  When this is done, suction should be felt at the connection -arrow- for approx. 1...3 seconds.