Description - VP-20 Pump (31): Overview
FIGURE 1 ELECTRONIC CONTROL ASSEMBLY:
FIGURE 2 ENGINE COOLANT TEMPERATURE SENSOR:
DESCRIPTION
The VP-20 fuel injection pump used on 2.4L diesel engines in California functions the same way as the VE pump used on the 49 state version, except for the method used for controlling pump timing. The pump is controlled by an electronic control assembly mounted in the luggage compartment (Fig. 1).
FIGURE 3 POSITION SENSOR:
FIGURE 4 LIFT SENSOR CONNECTOR, NO. 4 INJECTOR:
FIGURE 5 FUEL CONTROL SOLENOID:
The control assembly processes information from the engine coolant temperature sensor (Fig. 2), the position sensor (Fig. 3) and the lift sensor located in the No. 4 injector (Fig. 4) and varies the injection timing according to this information. To change the injection timing, the control assembly controls the cycling of the fuel control solenoid in the injection pump (Fig. 5). The solenoid varies the fuel pressure available to the advance piston by providing an additional pressure bleed, whenever it is open. By cycling the solenoid the control assembly can precisely control the fuel pressure at the advance piston and therefore control injection timing.
The system has a built-in diagnostic capability which will light the "Check Turbo" warning indicator when there is a problem in the system.
VP-20 System
Identification of VP-20 Injection Pump
The following items can be used to distinguish between the VE pump and the VP-20 pump:
VE Pump
^ Engine Calibration Code - 4-40 AR xx
^ One injector nozzle with lift sensor pigtail in cylinder No. 4.
^ Cold start advance solenoid on LH side of injection pump.
^ 30~F temperature switch in cylinder head.
VP-20 Pump
^ Engine Calibration Code - 4-40 SR xx
^ Two injector nozzles with lift sensor pigtails (cylinders No. 4 and 5).
^ No cold start advance solenoid on LH side of injection pump.
^ Injection timing advance solenoid at bottom rear of injection pump with 305-356 mm (12-14 inch pigtail). Connector snaps into bracket above No. 5 injector.
^ Electronic control assembly mounted in luggage compartment.
^ Electronic control assembly power relay mounted on dash panel near glow plug module.
NOTE: The glow plug system, fuel shut-off solenoid and the message center fuel flow interface module are separate from the electronic control assembly. Diagnosis for these systems can be found in the Engine/Emissions Diagnosis Manual, Section 31.
NOTE: The fuel flow interface system for the message center uses the lift sensor in injector nozzle No. 5, NOT the lift sensor in injector nozzle No. 4.
Exhaust Gas Recirculation (EGR)
The vacuum portion of the VP-20 EGR system can be checked out using the EGR system diagnosis in the Engine/Emissions Diagnosis Manual, Section 31, up to and including Test Step H14. However, if a problem still exists, GO to Step N3 of Engine Performance Diagnosis - Electronic Control Assembly in this TSB.
VP-20 System
VP-20 System Diagnosis
The following VP-20 system problems are covered in the diagnostic procedures in this TSB:
^ "Check Turbo" warning indicator is lit.
^ Timing is not within specification.
^ Excessive engine noise - warm engine.
^ Excessive smoke.
^ Lack of power.
^ Hard starting cold and hard starting warm.
^ EGR not functioning.
If any of these problems cannot be corrected using the procedures in the Engine/Emissions Diagnosis Manual, Section 31, or if the fuel injection pump and/or electronic control assembly is suspect, refer to the Diagnosis Procedures in this TSB.
NOTE: The "Check Turbo" warning indicator performs two functions:
^ Indicates fault in turbocharger.
^ Indicates fault in electrical portion of VP-20 injection system.