Pickup & 4Runner
- Warm up engine. Disconnect hose from distributor sub-diaphragm, and plug end of hose. Check ignition timing. Timing should be 0 degrees BTDC at 950 RPM maximum. Reconnect hose to sub-diaphragm. Verify that timing advances to about 12 degrees BTDC at 950 RPM maximum.
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- Disconnect vacuum hose between check valve and vacuum pipe at vacuum pipe side. Plug pipe end. Ignition timing should remain stationary for more than one minute. Stop engine and reconnect hoses to proper locations.
- Remove 3 hoses from ports on top of HAC valve. Blow air into each hose and check that air flows into carburetor. Reconnect hoses to proper locations.