Cold Engine Control Pressure Test

NOTE: On 930 Turbo, cold engine control pressure cannot be checked due to the design of its control pressure regulator.

With engine cold, turn ignition on. Unplug connector at airflow sensor and control pressure regulator. On 928, unplug connector at auxiliary air regulator. Pull out fuel pump relay (in passenger's footwell) and bridge terminals No. 87 and 30 to turn on fuel pump.
On all models, open valve and read pressure on gauge. On 928, cold engine control pressure should be as indicated in 928 COLD ENGINE CONTROL PRESSURE TEST table.
On all other models, compare readings with cold engine control pressure graph. See Fig 1. If pressures are incorrect, replace control pressure regulator.

Fig 1: Cold Engine Control Pressure Graphs
Courtesy of NOT AVAILABLE

928 COLD ENGINE CONTROL PRESSURE TEST ⁽¹⁾

Application

psi (kg/cm² )

Engine Not Running

16.7-21.0 (1.17-1.48)

Engine At Idle Speed

23.9-28.3 (1.68-1.99)

⁽¹⁾	Measured at ambient temperature of 68°F (20°C).