Fuel Injection Pump - Adjustable Pressure Regulators
85chevy0784-233
6C (VIm)
Jan., 1985
Subject: DIESEL FUEL INJECTION PUMP PRESSURE REGULATORS (EXCEPT CALIFORNIA)
Model and Year: 1984 IMPALA, CAPRICE, MONTE CARLO, EL
CAMINO, AND CELEBRITY WITH 4.3L V6 OR 5.7L V8 DIESEL ENGINE
TO: ALL CHEVROLET DEALERS
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 Pressure Engine Warm" in the 1984 Chassis 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, and NB2 California.
The procedure for checking housing pressure contains the information on how to check housing pressure and also the specifications and diagnosis if necessary.
FIGURE 1:
FIGURE 2:
ADJUSTING HOUSING PRESSURE REGULATORS
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.
The Housing Pressure Regulators are adjusted by rotating the adjusting 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.
CHECKING INJECTION PUMP HOUSING FUEL PRESSURE - EXCEPT CALIFORNIA
Tools required:
^ J-28552 Gauge or any accurate 0-105 kPa (0-15 psi) Pressure Gauge.
^ J-34151 Housing Pressure Adapter.
^ J-29657 Manifold Screen Covers - V6 Diesel Engine.
^ J-26925 Tachometer.
^ J-26996-1 Air Crossover Cover.
^ J-26996-10 Manifold Screen Covers - V8 Diesel Engine.
FIGURE 3:
FIGURE 4:
Figures 3 and 4 are diagnostic flow charts for checking housing pressure to determine if it is correct and also what to do if it isn't. Next to some "boxes" in the chart are footnotes ("A", "B", etc.). These footnotes are listed below. This was done to reduce "clutter" in the chart. Refer to the footnotes as required.
"A"
1. Block the drive wheels and firmly apply the parking brake. Shift the transmission/transaxle to "P" (Park).
2. Start the engine and let run at idle until fully warmed up. Then shut off the engine.
3. Remove the air cleaner and install air crossover cover J-26996-1.
4. Disconnect the fuel return pipe from the pump.
5. Remove the return line connector and housing pressure regulator as an assembly.
6. Install adapter J-34151 in the pump cover.
7. Install the return line connector and housing pressure regulator into J-34151 and connect the return pipe to the return line connector.
8. Attach a pressure gauge to J-34151.
9. Install J-26925 tachometer.
10. Disconnect the HPAA lead.
11. Start the engine. Inspect for fuel leaks and correct them.
12. Increase the idle speed to 1,000 rpm and note pressure.
"B"
1. Shut off the engine.
2. Remove the line fitting from the pressure regulator.
3. Insert a 1/8" HEX key into the pressure regulator (Figure 2). Rotate the adjustment screw clockwise to increase pressure, counterclockwise to decrease pressure. Adjust the pressure regulator to obtain 68.95
kPa (10 psi). One turn of the screw will change housing pressure 22 kPa (3.2 psi).
4. Check and reset timing. See "Checking and/or Adjusting Timing," in Section 6C5 of the 1984 Chassis Service Manual.
"C"
When housing pressure is this low, the HPCA pressure regulator check ball is either not seated or partially seated because of a fault in the pressure regulator.
1. Remove the pressure regulator from the adapter.
2. Using a maximum of 207 kPa (30 psi) of air pressure, blow through the regulator from the pump side first and then from the outlet side. The check ball should seat when blowing through the outlet side.
CAUTION: Safety glasses must be worn when using compressed air to avoid injury to the eyes.
3. Replace the pressure regulator if it is faulty. If debris is found in the regulator, remove the injection pump cover to determine the source.
"D"
1. Disconnect the HPAA solenoid at the pump to HPAA pipe.
2. Install a hose over the pipe outlet and put the other end of the hose into a container.
3. Start the engine.
4. If housing pressure is now 62-75.8 kPa (9-11 psi), either the return pipes, hoses or tank unit are restricted.
"E"
1. Reconnect the pump return pipe to the HPAA solenoid.
2. Disconnect the return pipe (tank side) from the HPAA solenoid.
3. Place a hose over the HPAA outlet and put the other end of the hose into a container.
4. Start the engine.
"F"
1. Remove HPAA solenoid assembly from the engine.
2. Using a maximum of 207 kPa (30 psi) of air pressure, blow through the assembly from the pump side first and then from the outlet side. Air should flow in both directions. If not, replace the assembly.
CAUTION: Safety glasses must be worn when using compressed air to avoid injury to the eyes.
3 . Remove the pressure regulator from the solenoid.
4. See if the solenoid plunger is free to move. If not, replace the assembly.
5. To check solenoid operation:
a. Ground the solenoid housing using a jumper lead to a 12V battery's negative terminal.
b. Attach another jumper lead to the same 12V battery's positive terminal and connect this jumper to the solenoid lead terminal.
c. The solenoid plunger should move inward with 12V applied and move fully back when the jumper is disconnected.
6. To adjust the HPAA pressure regulator:
a. Install the HPAA assembly onto the fuel return pipes.
b. Connect a jumper lead to the positive terminal of the battery. Connect the jumper to the HPAA solenoid lead terminal.
c. Start the engine and record housing pressure. It should be:
Low Altitude (NA5) - 103.42-131 kPa (15-19 psi)
V6 engine.
93-120.66 kPa (13.5-17.5 psi) V8 engine.
High Altitude (NA6) - 75.8-103.38 kPa (11-15 psi)
V6 engine VIN Code T.
68.9-96.48 kPa (10-14 psi) V6 engine VIN Code V.
93-120.6 kPa (13.5-17.5 psi) V8 engine.
d. If housing pressure is not within specification:
1. Disconnect the jumper to the HPAA.
2. Housing pressure should now be 62-75.8 kPa (9-11 psi). If not, adjust the housing pressure regulator.
3. Reconnect the jumper to the HPAA. Record the housing pressure. If not 89.63-117.21 kPA (13-17 psi), adjust the HPAA pressure regulator.
4. Remove the HPAA assembly from the engine.
5. Remove the line fitting from the pressure regulator.
6. Insert a 1/8" HEX key in the regulator (Figure 2). Rotate the adjustment screw clockwise to increase pressure, counterclockwise to decrease pressure. One turn of the screw will change housing pressure 22 kPa (3.2 psi).
"G"
When checking housing pressure using J-34151 adapter, it is not possible to unseat the housing pressure regulator with the HPCA. Normally, when the HPAA solenoid is on, so is the HPCA solenoid. With both solenoids on, the housing pressure regulator is unseated (not regulating) and the HPAA pressure regulator is regulating. Therefore, above about 1,200m (4,000 ft.) of elevation, actual housing pressure should be 27.58-41.37 kPa (4-6 psi). But with tool J-34151, the pressure reading is the housing pressure with both the HPCA and HPAA regulators regulating.
To check if the HPCA solenoid is operating, remove the J-34151 adapter and install the housing pressure regulator and return line connector into the pump cover. Connect the return fuel line. Disconnect the HPCA lead from the HPCA solenoid terminal. Start the engine. Using a jumper lead, apply 12 volts to the HPCA solenoid terminal.With the solenoid energized, there will be an increase in engine speed.
"H"
When checking housing pressure using J-34151 adapter, it is not possible to unseat the housing pressure regulator with HPCA. When the car is operated below 1,200m (4,000 ft.) of elevation, the HPAA solenoid is energized and regulating. With both pressure regulators operating, housing pressure is increased. Below 1,200m (4,000 ft.) of elevation, housing pressure should be:
75.8-103.38 kPa (11-15 psi) V6 engine VIN Code T.
68.9-96.48 kPa (10-14 psi) V6 engine VIN Code V.
93-120.6 kPa (13.5-17.5 psi) V8 engine.
To check if the HPCA solenoid is operating, remove the J-34151 adapter and install the housing pressure regulator and return line connector into the pump cover. Connect the return fuel line. Disconnect the HPCA lead from the HPCA solenoid terminal. Start the engine. Using a jumper lead, apply 12 volts to the HPCA solenoid terminal. With the solenoid energized, there will be an increase in engine speed.