1977 Ford Bronco Automatic TransFACTORY OEM SERVICE PROCEDURE

CSSA System

  1. Using a vacuum "T", connect a vacuum gauge in-line with distributor vacuum advance. Start engine. Open throttle to about 2500 RPM and release throttle while observing vacuum gauge.
  2. With engine coolant temperature below 125°F, vacuum should rise with throttle opening, then fall slowly as vacuum is passed through RDV. If vacuum falls quickly, replace RDV.
  3. With engine temperature between 125°F and 235°F, ported vacuum should be delayed as throttle is opened, and fall with throttle closing. If vacuum is not delayed as throttle is opened, replace SDV. If vacuum reading in steps  2 and 3)  are identical (same or no delay), CSSA PVS is defective.
  4. Coolant PVS can be checked (if necessary) by causing engine coolant temperature to rise above 235°F. Coolant PVS should close ported vacuum port and open intake manifold port to distributor vacuum advance. If coolant PVS does not switch to manifold vacuum above 235°F, then switch back to ported vacuum when coolant temperature falls below 235°F, replace PVS.
    Fig 1: Cold Start Spark Advance (CSSA) System
    G09327223Courtesy of FORD MOTOR CO.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.