DESCRIPTION Chevrolet Chevy Van 5.7L Eng G20. Service Manual: FUEL INJECTION SYSTEM - TBI

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1 Service Manual: FUEL INJECTION SYSTEM - TBI DESCRIPTION 1989 Chevrolet Chevy Van 5.7L Eng G20 The throttle body fuel injection system consists of 7 major sub-assemblies: fuel supply system, throttle body assembly, Idle Air Control (IAC) system, Electronic Control Module (ECM), Electronic Spark Timing (EST), data sensors, and emission controls. Fuel is supplied to the engine through electronically pulsed injector(s), located in the throttle body assembly on top of intake manifold. The ECM controls the amount of fuel metered through the injector(s) based upon engine demand. 1/37

2 Fig 1: Throttle Body Identification Location Courtesy of GENERAL MOTORS CORP. OPERATION > THROTTLE BODY ASSEMBLY The model 220 throttle body assembly consists of a fuel meter cover with a built in fuel pressure regulator, a fuel meter body with 2 fuel injectors, a throttle body with 2 throttle valves, an Idle Air Control (IAC) valve, and a Throttle Position Sensor (TPS). The model 700 throttle body assembly consists of a fuel meter body with one fuel injector, a fuel pressure regulator, a throttle body with one throttle valve, an IAC valve, and a TPS sensor. 2/37

3 The throttle body portion may contain ports located above or below the throttle valve to generate vacuum signals for EGR valve, MAP sensor, and fuel vapor canister purge system. OPERATION > FUEL SUPPLY SYSTEM An electric fuel pump (located inside fuel tank as an integral part of the fuel gauge sending unit) supplies fuel under pressure to the throttle body assembly. On most engines, a fuel pump relay controls fuel pump operation. When the ignition is on, the fuel pump relay activates the fuel pump for 2 seconds to prime the injector(s). On 5.7L engines over 8500 GVW, "G" series with 5.7L and all 7.4L engines, a fuel module circuit is installed so that the fuel pump will run for 20 seconds when ignition is turned on. This enables engine to start easily during high ambient temperatures. On all engines, if the ECM does not receive reference pulses (engine cranking) from the distributor after this priming period, the ECM deactivates the fuel pump relay. The fuel pump relay will be activated again when the ECM receives distributor reference pulses. As a back-up system to the fuel pump relay, the fuel pump can also be activated by oil pressure sending unit. The sending unit has 2 internal circuits. One circuit operates the oil pressure indicator in the instrument panel. The second circuit is normally an open switch which closes when the oil pressure reaches about 4 psi (.3 kg/cm 2 ). If fuel pump relay fails, oil pressure sending unit will close, and supply voltage to fuel pump. OPERATION > FUEL PRESSURE REGULATOR The pressure regulator is a diaphragm-operated relief valve with injector pressure acting on one side and atmospheric pressure acting on the other. The pressure regulator maintains a constant pressure drop of about 10 psi (.7 kg/cm 2 ) across injector(s), throughout all engine operating conditions. The model 700 fuel pressure regulator may be disassembled and repaired. OPERATION > FUEL INJECTOR The fuel injector is a solenoid-operated device controlled by the ECM. The ECM activates the solenoid which lifts a normally closed ball valve off its seat. Fuel under pressure is injected in a conical spray pattern at the walls of throttle body bore, above the throttle valve. Excess fuel passes through the pressure regulator and is returned to the fuel tank. OPERATION > IDLE AIR CONTROL (IAC) SYSTEM The IAC system consists of an electrically controlled motor (actuator) which positions the IAC valve in the air by-pass channel around the throttle valve. The ECM calculates the desired position of the IAC valve based upon battery voltage, coolant temperature, engine load, and engine RPM to control idle speed while preventing stalls due to engine load changes. OPERATION > ELECTRONIC CONTROL MODULE (ECM) The Electronic Control Module (ECM) receives and processes information from all data sensors to produce the proper pulse duration ("on" time) for the injector(s), correct idle speed and proper spark timing. The ECM performs calculations to control the following operating 3/37

4 conditions: engine start, engine running, fuel enrichment during acceleration, lean fuel mixture during deceleration, fuel cut-off and battery voltage correction. If the engine is flooded, the driver must depress the accelerator pedal all the way down. At this position, the ECM calculates injector pulse width equal to an air/fuel ratio of 20:1. This air/fuel ratio will be maintained as long as the throttle valve remains wide open and engine speed is below 600 RPM. If the throttle position becomes less than 80 percent open and/or engine speed exceeds 600 RPM, the ECM changes the injector pulse width to that used during engine starting. OPERATION > DATA SENSORS NOTE: For information on other sensors that are used by the ECM to control engine performance and other systems,refer to the TBI CEC TESTING/CODES article in the COMPUTERIZED ENGINE CONTROLS section. OPERATION > DATA SENSORS > COOLANT TEMPERATURE SENSOR (CTS) The coolant temperature sensor is located in thermostat housing. It is a variable resistor (thermistor) type sensor, and transmits an electrical signal to the ECM proportionate to engine temperature. A low coolant temperature produces a high resistance while a high coolant temperature produces a low resistance. Coolant temperature is used for fuel management, idle air control, spark timing, EGR operation, canister purge operation and other engine operating functions. OPERATION > DATA SENSORS > OXYGEN SENSOR The oxygen sensor monitors the oxygen content of the exhaust gases. As the oxygen content of the exhaust gases increases relative to the surrounding atmosphere, a lean fuel mixture is indicated by a low voltage output. As the oxygen content decreases, a rich fuel mixture is indicated by a higher voltage output. The ECM interprets the electrical signal and adjusts the injector pulse width to maintain the air/fuel ratio close to 14.7:1. OPERATION > DATA SENSORS > MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR The MAP sensor is a variable resistor which measures the changes in the intake manifold pressure which result from engine load and speed changes. The pressure measured by the MAP sensor is the difference between barometric pressure (atmospheric air) and manifold pressure (vacuum). OPERATION > DATA SENSORS > THROTTLE POSITION SENSOR (TPS) The TPS is mounted on side of the throttle body and is connected to the throttle shaft. As throttle valve angle changes, the resistance of the sensor also changes. The ECM supplies a 5- volt reference signal to the TPS. A closed throttle condition produces high resistance at the sensor and the output signal to the ECM will be low (about.5 volt). A wide open throttle condition produces low resistance at the sensor. The output signal to the ECM will be high (about 5 volts). 4/37

5 APPLICATION ROCHESTER THROTTLE BODY Application Part No. Astro & Safari 2.5L L "C/K" Series 4.3L L L Heavy Duty (GVW ,000 Lbs.) Automatic Transmission Manual Transmission L Light Duty (GVW Below 8500 Lbs.) L "G" Series 4.3L L L Light Duty (GVW Below 8600 Lbs.) Medium Duty (GVW ,000 Lbs) Heavy Duty (GVW Above 10,000 Lbs) Automatic Transmission Manual Transmission L "P" Series 5.7L Automatic Transmission Manual Transmission L Automatic Transmission /37

6 Manual Transmission "R/V" Series 5.7L Automatic Transmission Manual Transmission "R" Series Only "V" Series Only L "S" Series 2.5L L (2WD) Automatic Transmission Manual Transmission L (4WD) L Automatic Transmission Manual Transmission Part No. Not Available IDENTIFICATION The throttle body injection identification number is stamped on mounting flange, on throttle lever side. See Figure. Alphabetical code letters are stamped on the throttle body at external tube locations to identify vacuum hose connections. All 4-cylinder engines are equipped with model 700 TBI unit. The V6 and V8 engines use model 220 TBI unit. SYSTEM TESTING NOTE: For diagnosis, refer to the TBI CEC TESTING/CODES article in the COMPUTERIZED ENGINE CONTROLS section. SYSTEM TESTING > FUEL SYSTEM PRESSURE RELIEF 1. On model 700 TBI unit, disconnect 3-terminal electrical connector at fuel tank. Start engine and allow to run until engine stalls due to lack of fuel. Crank engine for 3 seconds to remove any fuel pressure left in fuel lines. Fuel lines are now safe for servicing. 6/37

7 2. On model 220 TBI unit, fuel pressure is relieved and drops to zero when ignition is turned off. To minimize the risk of fire and personal injury, cover area to be disconnected with a shop rag. SYSTEM TESTING > FUEL SYSTEM PRESSURE 1. Turn engine off and relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF. Remove air cleaner and plug air cleaner (THERMAC) vacuum port (if equipped). 2. Disconnect fuel line between throttle body and fuel filter. Install Fuel Pressure Gauge (J-29658A) and Adapter (J-2968A-85) between throttle body and in-line fuel filter. Start engine and observe fuel pressure reading. 3. Fuel pressure should be 9-13 psi (.6-.9 kg/cm ). If not, see CHART A-6, FUEL SYSTEM PRESSURE TEST in the CCC TBI TESTING/CODES article in the COMPUTER ENG CONTROL section. 4. After testing, relieve fuel pressure. Remove fuel pressure gauge and connect fuel line to fuel filter. Start vehicle and check for leaks. Remove plug from throttle body vacuum port (if equipped). Install air cleaner. REMOVAL & INSTALLATION > INFORMATION 2 NOTE: For removal and installation of data sensors not covered, see the CCC TBI TESTS W/CODES article in the COMPUTER ENG CONTROL section. REMOVAL & INSTALLATION > THROTTLE BODY ASSEMBLY > REMOVAL 1. Disconnect air cleaner (THERMAC) hose from engine fitting (if equipped). Remove air cleaner, adapter, and gasket. Disconnect electrical leads at IAC valve, throttle position sensor, and fuel injector(s). 2. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF. Disconnect fuel lines from throttle body. Discard fuel line "O" rings. Disconnect grommet with wires from throttle body. NOTE: On model 220 TBI units, squeeze plastic tabs on injectors and pull straight up. 3. Disconnect throttle linkage, return spring and cruise control linkage (if equipped). Label and disconnect all vacuum hoses from throttle body. Remove throttle body mount bolts/nut. Remove throttle body. REMOVAL & INSTALLATION > THROTTLE BODY ASSEMBLY > INSTALLATION To install, reverse removal procedure. Ensure throttle body and intake manifold sealing surfaces are clean. Always use new throttle body gasket and fuel line "O" rings. Check fuel system for 7/37

8 leaks by turning ignition on, but without starting engine. REMOVAL & INSTALLATION > FUEL PUMP 1. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELIEF. Disconnect battery negative cable. Raise vehicle on hoist and lower fuel tank. Turn lock ring counterclockwise and remove fuel lever sending unit and pump assembly. 2. Remove fuel pump from fuel lever sending unit by pulling fuel pump up into attaching hose while pulling outward away from bottom support. Ensure rubber insulator and strainer are not damaged. To install, reverse removal procedure. REMOVAL & INSTALLATION > FUEL PUMP RELAY Remove electrical connector, mounting screws, and relay. To install, reverse removal procedure. See Fig 1 through Fig 14 for locations of the fuel pump relay. 8/37

9 Fig 1: "S" & "T" Series 2.5L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 9/37

10 Fig 2: "S" & "T" Series 2.8L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 10/37

11 Fig 3: "S" & "T" Series 4.3L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 11/37

12 Fig 4: Astro & Safari 2.5L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 12/37

13 Fig 5: Astro & Safari 4.3L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 13/37

14 Fig 6: "G" Series 4.3L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 14/37

15 Fig 7: "G" Series 5.0L & 5.7L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 15/37

16 Fig 8: "G" Series 7.4L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 16/37

17 Fig 9: "C" & "K" Series 4.3L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 17/37

18 Fig 10: "C" & "K" Series 5.OL & 5.7L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 18/37

19 Fig 11: "C" & "K" Series 7.4L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 19/37

20 Fig 12: "R" & "V" Series 5.7L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 20/37

21 Fig 13: "R" & "V" Series 7.4L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. 21/37

22 Fig 14: "P" Series 5.7L TBI/CCC Component Locations Courtesy of GENERAL MOTORS CORP. REMOVAL & INSTALLATION > THROTTLE POSITION SENSOR (TPS) > REMOVAL & INSTALLATION 22/37

23 1. Remove air cleaner assembly. Disconnect electrical lead from TPS sensor. Remove attaching screws, lock washers, retainers, and TPS sensor. To install, reverse removal procedure. On 2.8L engines, adjust TPS to specification. See ADJUSTMENTS in this article. Use Loctite on TPS attaching screws. 2. On model 220 TBI units, all 2.8L and 7.4L engines use a horizontal electrical connector on the TPS. All other engines with model 220 TBI units, use a vertical electrical connector on the TPS. The sensor mounting configurations are the same. When replacing a TPS ensure correct part number is used. WIRING DIAGRAMS 23/37

24 Fig 1: Astro & Safari 2.5L TBI/CCC Wiring Diagram 24/37

25 Fig 2: Astro & Safari 4.3L TBI/CCC Wiring Diagram 25/37

26 Fig 3: "C" & "K" Series 4.3L, 5.0L, 5.7L & 7.4L TBI/CCC Wiring Diagram 26/37

27 Fig 4: "G" Series TBI/CCC Wiring Diagram 27/37

28 Fig 5: "P" Series TBI/CCC Wiring Diagram 28/37

29 Fig 6: "R" & "V" Series TBI/CCC Wiring Diagram 29/37

30 Fig 7: "S" & "T" Series 2.5L TBI/CCC Wiring Diagram 30/37

31 Fig 8: "S" & "T" Series 2.8L & 4.3L TBI/CCC Wiring Diagram ADJUSTMENTS > MINIMUM AIR RATE NOTE: Verify correct controlled idle speed. Perform idle air control check before 31/37

32 adjusting minimum air rate. Refer to the CCC TBI TESTS W/CODES article in the COMPUTER ENG CONTROL section. 1. Remove air cleaner and gasket. With Idle Air Control (IAC) valve connected, ground terminal "A" to "B" at ALDL connector. refer to the CCC TBI TESTS W/CODES article in the COMPUTER ENG CONTROL section. 2. Turn ignition on, DO NOT start engine. Wait approximately 30 seconds for IAC valve pintle to extend and seat in throttle body. 3. With ignition on, disconnect IAC valve electrical connector. Remove ground at ALDL connector. Using an awl, remove plug for minimum idle speed adjustment by piercing, then applying leverage. 4. Install a tachometer and start engine. Allow engine to reach operating temperature. Adjust idle screw to specification with vehicle in Neutral. Turn ignition off. Reconnect IAC valve electrical connector. Install air cleaner and gasket. 5. This procedure will set a code 35. Erase code by disconnecting electrical power to ECM for 30 seconds. ADJUSTMENTS > TPS (2.8L ONLY) Connect digital voltmeter between TPS connector terminals "A" and "B" using jumper wires. With ignition on and engine stopped, TPS voltage should be between.42 and.54 volt. Rotate TPS to obtain correct voltage reading. If voltage cannot be adjusted to proper specification, replace TPS. TORQUE SPECIFICATIONS TORQUE SPECIFICATIONS Application Ft. Lbs. (N.m) Fuel Inlet Nut 30 (41) Fuel Outlet Nut 21 (28) Idle Air Control Valve (Threaded) 13 (18) Throttle Body-to-Manifold Bolts 2.8L 18 (24) All Other Engines 12 (16) INCH Lbs. (N.m) Fuel Meter Body Screws Model (3) Model (6) 32/37

33 Fuel Meter Cover Screws (Model 220 Only) 28 (3) Fuel Pressure Regulator Screws (Model 700 Only) 22 (2.5) Idle Air Control Valve Screws (Flange Mounted) 28 (3) MODEL 220 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 220) > FUEL METER COVER 1. Remove throttle body and place assembly on Holding Fixture (J ) to prevent damage to throttle valves. Disconnect electrical leads from fuel injectors. Remove cover attaching screws and lock washers. See Figure. 2. Lift off fuel meter cover with fuel pressure regulator assembly attached. DO NOT remove fuel meter cover gasket at this time. Remove fuel pressure regulator dust seal from fuel meter body. WARNING: Fuel pressure regulator is not serviceable. Do not remove pressure regulator from fuel meter cover. The pressure regulator includes a spring under heavy tension which may cause personal injury if released. DO NOT immerse cover and regulator assembly in any type of cleaning solvent. MODEL 220 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 220) > FUEL INJECTOR 1. With fuel meter cover gasket in place, use a screwdriver and fulcrum to carefully pry injectors away from fuel meter body. Carefully lift injectors out with a twisting motion. See Fig Remove small "O" ring from nozzle end of injector. Carefully rotate injector filter back and forth to remove from base of injector. Remove large "O" ring and back-up washer from top of injector cavity. 33/37

34 Fig 1: Removing Fuel Injector Assembly Courtesy of GENERAL MOTORS CORP. MODEL 220 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 220) > FUEL METER BODY Remove fuel inlet and outlet nuts and gaskets from fuel meter body. Remove fuel meter body attaching screws and lock washers. Remove fuel meter body and gasket. MODEL 220 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 220) > THROTTLE BODY Remove throttle position sensor. Invert throttle body assembly and place on clean, flat surface. Remove screws and idle air control valve (7.4L engine) or remove idle air control valve by using a 1 1/4" (32 mm) wrench. MODEL 700 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 700) > FUEL INJECTOR 1. Remove throttle body and place assembly on Holding Fixture (J ) to prevent damage to throttle valves. Remove screw and injector retainer. See Figure. 2. Use a screwdriver and fulcrum to carefully pry injector away from fuel meter body. See Fig 1. Remove upper and lower "O" rings from injector or fuel injector cavity. 34/37

Fig 1: Removing Fuel Injector Assembly Courtesy of GENERAL MOTORS CORP. MODEL 700 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 700) > FUEL METER BODY 1.

35 Fig 1: Removing Fuel Injector Assembly Courtesy of GENERAL MOTORS CORP. MODEL 700 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 700) > FUEL METER BODY 1. Remove fuel pressure regulator attaching screws while keeping pressure regulator compressed. Remove pressure regulator cover, spring seat, spring, and diaphragm. See Figure. WARNING: The pressure regulator includes a spring under heavy tension which may cause personal injury if released. Use care when servicing regulator. 2. Inspect pressure regulator seat for pitting or other damage. If damaged, replace fuel meter body. To replace fuel meter body, remove fuel meter body screws and washers. Remove fuel meter body from throttle body. Remove and discard fuel meter body gasket. MODEL 700 THROTTLE BODY OVERHAUL > DISASSEMBLY (MODEL 700) > THROTTLE BODY Remove tube assembly and gasket. Remove throttle position sensor and Idle Air Control (IAC) valve. MODEL 700 THROTTLE BODY OVERHAUL > CLEANING & INSPECTION Clean all metal parts in a cold immersion-type cleaner and blow dry with compressed air. DO NOT immerse throttle position sensor, idle air control valve, fuel injector(s), fuel filter, 35/37

36 or fuel meter cover and pressure regulator assembly in cleaning solvent. Inspect throttle body assembly casting surfaces for damage. Fig 1: Exploded View of Model 700 Throttle Body Assembly Courtesy of GENERAL MOTORS CORP. 36/37

37 MODEL 700 THROTTLE BODY OVERHAUL > REASSEMBLY (MODEL 700) > THROTTLE BODY 1. Install tube assembly using a new gasket. Install throttle position sensor. Before installing idle air control valve, measure distance between tip of valve pintle and mounting surface. Distance should not exceed 1 1/8" (28 mm). 2. If distance is incorrect, exert firm pressure on pintle while moving pintle from side to side until distance is correct. The flange mounted IAC valve on 2.5L engines has a dual taper, 10 mm diameter pintle. Ensure replacement valve has same shape and diameter of valve removed. MODEL 700 THROTTLE BODY OVERHAUL > REASSEMBLY (MODEL 700) > FUEL METER BODY 1. Install new fuel meter body gasket. Ensure gasket cut-outs match openings in throttle body. Install fuel meter body and tighten screws. Install new pressure regulator diaphragm. Ensure diaphragm is seated in fuel meter body groove. 2. Install spring, spring seat, and cover. See Figure. Apply Loctite to pressure regulator cover screws. While maintaining pressure on regulator cover and spring, install cover screws. MODEL 700 THROTTLE BODY OVERHAUL > REASSEMBLY (MODEL 700) > FUEL INJECTOR NOTE: Injectors from other TBI units will fit in the model 700 TBI unit. Injectors have different flow rates. Ensure correct part number is used. 1. Lubricate "O" rings with automatic transmission fluid. Make sure upper "O" ring is in groove and that lower "O" ring is flush against filter. See Figure. 2. Press injector into fuel cavity. Ensure injector electrical connector is facing cut-out in fuel meter body for wire grommet. Apply Loctite to injector retainer screw. Install injector retainer and screw. 37/37

IGNITION TIMING (GASOLINE)

IGNITION TIMING (GASOLINE) 4-CYLINDER IGNITION TIMING 2.5L (VIN E) 1. Set parking brake, block drive wheels and place transmission in Neutral or Park. Warm engine to normal operating temperature. Turn