Diesel Fuel Pump - Pressure Regulators: Overview

Number 84-6(Diesel)-18 Date 1/85


Subject: DIESEL FUEL INJECTION PUMP PRESSURE REGULATORS (EXCEPT CALIFORNIA)

MODELS AFFECTED: 1984 6000, GRAND PRIX, & PARISIENNE WITH 4.3L V-6 OR 5.7L V-8 DIESEL ENGINE

The 1984 4.3L and 5.7L injection pump Housing Pressure Cold Advance (HPCA) regulator and Housing Pressure Altitude Advance (HPAA) regulators are adjustable. The housing pressure regulator on California (NB2) cars is NOT adjustable.. Changes in housing pressure has an effect on timing which effects emissions, cold starts, idle quality, white smoke and noise level.

These procedures for checking and adjusting the housing pressure regulators replace "Checking Injection Pump Housing Fuel PressureEngine Warm" in the 1984 Service Manuals, Section 6C5. The following diagnosis applies to Low Altitude (NA5) and High Altitude (NA6) equipped cars only. To find out which system a car was assembled with, refer to the Service Parts Identification Label. It will disclose the system with coding as follows: NA5 Low Altitude, NA6 High Altitude, NB2 Calfifornia.

The procedure for checking housing pressure contains the information on how to check housing pressure and also the specifications and diagnosis if necessary.


Adjusting Housing Pressure Requlators

The HPCA pressure regulator is installed in the pump cover with a fitting that adapts it to the fuel return pipe. The HPAA pressure regulator is installed in the "outlet" side of the HPAA solenoid which, is located in the fuel return pipe. It also has a fitting that adapts the fuel return line to it.

FIGURE 1:

FIGURE 2:

The Housing Pressure Regulators are adjusted by rotating the adjustment screw with a 1/8" HEX key. Rotating the adjustment screw clockwise (when viewed from the end that the tool is inserted) increases housing pressure. One turn of the screw will change housing pressure 22 kPa (3.2 psi). See Figures 1 and 2.