Hot Starting Fuel Pressure Regulator Control

Fig. 115 Pressure regulator control wiring circuit.:

The pressure regulator control, Fig. 115, is used to improve starting of a hot engine by cutting intake manifold pressure and increasing fuel pressure. The system operates when cylinder head temperature is above 212°F, during starting and will remain on for 3 minutes after engine has been started.

Fig. 116 Connector jumper wire between cylinder head temperature sensor terminals.:

Diagnosis

1. Disconnect cylinder head temperature sensor wire connector, then connect a jumper wire between sensor terminals, Fig. 116.

Fig. 117 Checking for vacuum at pressure regulator solenoid valve hose.:

2. Disconnect vacuum hose between pressure regulator and solenoid valve.
3. Start engine and check to ensure that vacuum does not exist for 3 minutes, Fig. 117.
4. If vacuum does exist, disconnect pressure regulator control modulator wire connector for modulator located under battery.

Fig. 118 Checking for continuity at pressure regulator control modulator wire connector terminal 84.:

5. Check solenoid valve and circuit as follows:
a. Check for continuity between wire connector terminal 85 and ground, with ignition switch in the Off position, Fig. 118. Continuity should not exist.

Fig. 119 Checking for voltage at pressure regulator control modulator wire connector terminals 80, 81, 83, 84.:

b. Place ignition switch in the On position and check for voltage at connector terminals 80, 81, 83 and 84 and ground, Fig. 119. Terminals 81, 83 and 84 should indicate battery voltage. Terminal 80 should indicate between 0 and 12 volts.

Fig. 120 Checking for continuity at pressure regulator control modulator wire connector terminal 82.:

c. Disconnect starter "S" terminal, then place ignition switch in start position and check for voltage between connector terminal 82 and ground, Fig. 120. Battery voltage should be indicated.

Fig. 121 Checking solenoid valve for continuity.:

d. Check for continuity between solenoid valve terminals, Fig. 121. Continuity should exist.
e. If solenoid valve and circuit are satisfactory, replace pressure control regulator control modulator.