LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 1978 >> Pickup Base, Automatic Trans >> Repair and Diagnosis >> Engine Mechanical >> Auxiliary Emission Control Systems >> High Altitude Compensation (HAC) System >> Testing >> High Altitude Compensation >> 1978 Models
July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

1978 Models

  1. On 20R and 2T-C engines, check ignition timing at idle and adjust if necessary. Disconnect vacuum hose from distributor sub-diaphragm. Timing should move about half-way toward TDC. Reconnect vacuum hose.
  2. Disconnect vacuum hose from Black side of delay valve and pinch hose. Ignition timing should remain at initial timing position for more than one minute. Reconnect hose and stop engine.
  3. On all engines, disconnect top hoses from HAC valve and blow into hoses one at a time. Check that air flows into carburetor. If not, check hoses and carburetor fittings for obstructions.
  4. Remove check valve from system. Blow into White side of check valve. Air should flow out. Blow into Black side of check valve. No air should flow. If valve does not operate as indicated, replace check valve.
scientia non olet · About LEMON Manuals