Hot Starting Fuel Pressure Regulator Control

Fig. 69 Pressure regulator control wiring circuit.:

The pressure regulator control, Fig. 69, is used on 1985---86 models to improve starting of a hot engine by cutting intake manifold pressure and increasing fuel pressure. The system operates when starting and for three minutes after starting when coolant temperature is above 203°F and vacuum at the vacuum switch is below 3.15 inches Hg.

Fig. 70 Connecting jumper wire between temperature sensor terminals.:

Diagnosis

1. Disconnect water temperature sensor electrical connector and connect suitable jumper wire between connector terminals, Fig. 70.
2. Disconnect vacuum hose between pressure regulator and solenoid valve.
3. Start engine and ensure vacuum does not exist for three minutes.

Fig. 71 Checking for continuity at pressure regulator control modulator connector.:

4. If vacuum does exist, disconnect pressure regulator control modulator electrical connector and check circuit and solenoid valve as follows:
a. Check for continuity between terminals 80, 83, 85, and ground, with ignition switch in the Off position, Fig. 71. Continuity should exist.

Fig. 72 Checking for voltage at pressure regulator control modulator connector w/ignition in On position.:

b. Measure voltage between terminals 81 and 84 and ground, Fig. 72, with ignition switch in the On position. Battery voltage should be indicated.

Fig. 73 Checking for voltage at pressure regulator control modulator connector w/ignition in Start position.:

c. Disconnect starter "S" terminal, then place ignition switch in start position and measure voltage between terminal 82 and ground, Fig. 73. Battery voltage should be indicated.

Fig. 74 Checking for continuity at solenoid valve connector.:

d. Check for continuity between solenoid valve terminals, Fig. 74. Continuity should exist.

Fig. 75 Checking for proper operation of vacuum switch.:

e. Check vacuum switch for proper operation using a suitable hand vacuum pump, Fig. 75.
f. If circuit, hoses, solenoid valve and vacuum switch are satisfactory, replace pressure regulator control modulator.