2.8l VIN [s] Pfi "a" Charts Chevrolet Camaro III рестайлинг

DIAGNOSTIC CIRCUIT CHECK

The Diagnostic Circuit Check is an organized approach for identifying fuel injection problems using the Assembly Line Data Link (ALDL). This communication link can provide diagnostic information for display on any "Scan" tester designed for this purpose. If the "Scan" tester is not operating, check tester on another vehicle. If okay, the cigar lighter socket should be checked for 12 volts and a good ground. With the ignition on, if the "Scan" tester reads "NO DATA" or "NO ALDL", check the serial data wire for an open or short to ground. Also check for an open diagnostic "test" terminal "B". Refer to appropriate CHART A1 schematic for circuit wiring reference. Refer to the appropriate PORT FUEL INJECTION - SCAN DATA SPECIFICATIONS table in the CCC EFI TESTS W/O CODES article for "SCAN DATA" tables.

Diagnostic Circuit Check Flow Chart. Scheme 296

Diagnostic Circuit Check. Scheme 297

NO "SERVICE ENGINE SOON" (SES) LIGHT (ALL EXCEPT "W" BODY)

The "SERVICE ENGINE SOON" (SES) light should be on steady when the ignition is on and the engine is not running. Battery voltage is supplied directly to the bulb. The ECM turns the light on by grounding circuit No. 419 at the ECM.

If both the "keep alive" memory and the battery voltage supply are lost or the ignition feed is not present, the "SERVICE ENGINE SOON" light will not come on.

Note. Test numbers refer to test numbers on diagnostic chart.

1. If fuse in holder is blown, refer to Code 54 mini schematic for complete circuit diagram.
2. Using a test light to 12 volts, probe each of the system grounds to determine if circuit is good.

Engine Runs Okay

Check for a faulty light bulb, circuit No. 419 open or fuel gauge fuse blown. This will result in no stop, oil or alternator warning lights. Engine Cranks But Will Not Run

Check for continuous battery power, open in fuse or fusible link, ECM fuse open, battery circuit No. 340 to ECM open, ignition circuit No. 439 to ECM open or poor plug connection at ECM.

Chart A1: No SES Light Schematic (2.8L F Body). Scheme 298

Chart A1: No "Service Engine Soon" (SES) Flow Chart. Scheme 299

NO "SERVICE ENGINE SOON" (SES) LIGHT (ALL EXCEPT "W" BODY). Scheme 300

CHART A2: NO ALDL OR NO CODE 12, "SES" LIGHT ON STEADY

"SERVICE ENGINE SOON" light should be on with ignition on and engine not running. Battery voltage is supplied directly to the bulb. With the diagnostic terminal grounded, the light should flash a Code 12, followed by any other trouble codes stored in memory. A steady light indicates a short to ground in light control circuit No. 419, or an open in circuit No. 451.

Note. Test numbers refer to test numbers on diagnostic chart.

1. If there is a problem with the ECM that causes a "Scan" tester not to read serial data, the ECM should not flash a Code 12. If Code 12 is flashing, check for a short in circuit No. 451. If Code 12 does not flash, be sure that "Scan" tester is working properly on another vehicle. If "Scan" tester is functioning properly and circuit No. 461 is okay, the PROM (2.8L, 5.0L and 5.7L F body, and 5.7L Y body), MEM-CAL or ECM may be at fault for the "NO ALDL" symptom.
2. If the light goes off when the ECM connector is disconnected, circuit No. 419 is not shorted to ground.
3. This test will check for an open in diagnostic circuit No. 451.
4. At this point, the wiring to the "SERVICE ENGINE SOON" light is okay. The problem could be a faulty ECM, PROM or MEM-CAL. If Code 12 does not flash, the ECM should be replaced using the original PROM or MEM-CAL. Replace the PROM or MEM-CAL only after trying a new ECM.

Chart A2: Flow Chart, No ALDL Or Won't Flash Code 12, "Service Engine Soon" Light On Steady. Scheme 301

CHART A3: ENGINE CRANKS BUT WON'T RUN (2.8L F BODY)

Note. Test numbers refer to test numbers on diagnostic chart.

1. This chart assumes that battery, condition and engine cranking speed are okay, and there is adequate fuel in the tank. If engine starts but immediately stalls, see CCC EFI TESTS W/O CODES article in this section. A "SERVICE ENGINE SOON" light is a basic check for ignition and battery supply to the ECM.
2. No spark indicates a basic ignition system problem.
3. This test will determine if the ECM is receiving the reference signal and controlling the injectors. This test could also be performed at the 4-way injector connector by using a test light between terminals "A" and "D". If the test light blinks while cranking, the ECM and wiring should be considered okay. How bright the light blinks is not important.
4. Using Pressure Gauge (J-34730-1), wrap a shop towel around the fuel pressure tap to absorb any fuel leakage that may occur when installing the gauge.
5. Checks for 12 volts to injectors.
6. This test will determine if the distributor module is not generating the reference pulse or if the wiring or ECM are at fault. Using a test light to battery voltage should generate a reference signal, causing the injector test light to blink.
7. Each time the test light touches circuit No. 430, the ECM should turn on the fuel pump for 2 seconds.
8. All checks made to this point would indicate that the ECM is at fault, however, there is a possibility of circuits No. 467 or 468 being shorted to a voltage source either in the engine harness or in the injector harness. To test for this condition, disconnect all injectors. Turn ignition on. Probe circuits No. 467 and 468 on the ECM side of injector harness with a test light connected to ground (test one injector harness on each side of engine). There should no light. If light is on, repair short to voltage. If okay, check resistance of the injectors. Resistance should be 10 ohms or more. Check injector harness connector. Be sure terminals are not backed out of connector and contacting each other. If all is okay, replace ECM.

DIAGNOSTIC AIDS

An EGR valve sticking open can cause a low air/fuel ratio during cranking. Unless engine enters "clear flood" at the first indication of a flooding condition, it can result in a no start condition. Check for fouled plugs.

If TPS is greater than 2.5 volts, the TPS is sticking or binding in the wide open throttle position. If this occurs, the engine may be in the "clear flood" mode. A defective cold start circuit or water in the fuel line can cause a no start condition in cold weather. To check the cold start circuit, see CHART A9.

A defective MAF sensor may cause a no start or a stall after start. To determine if the sensor is causing the problem, disconnect it. The ECM will then use a default value for the sensor. If the condition is corrected and the connections are okay, replace the sensor.

Also check that injectors on both sides of engine will cause a test light to blink. If not okay, check injector fuses. Check injector resistance. Resistance should be at least 8 ohms. If all checks are okay, see appropriate symptom in TROUBLE SHOOTING in THEORY & OPERATION section of this article.

Chart A3: Cranks But Won't Run Schematic (2.8L F Body). Scheme 302

Chart A3: Cranks But Won't Run Flow Chart (1 of 2). Scheme 303

Chart A3: Cranks But Won't Run Flow Chart (2 of 2). Scheme 304

Engine Cranks But Won't Run (2.8L F Body 1 of 2). Scheme 305

Engine Cranks But Won't Run (2.8L F Body 2 of 2). Scheme 306

CHART A7: FUEL SYSTEM DIAGNOSIS (1 Of 2)

ECM will turn on the in-tank fuel pump as long as the engine is cranking or running, and the ECM is receiving HEI distributor reference pulses.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Use Fuel Pressure Gauge (J-34730-1). Wrap a shop towel around the fuel pressure tap to absorb any fuel leakage that may occur when installing the gauge. With the ignition on and engine off, fuel pressure should about 40-47 psi (2.8-3.3 kg/cm 2 ). This pressure is controlled by spring pressure within the regulator assembly.
2. When the engine is idling, manifold vacuum is high and is applied to the fuel regulator diaphragm. This will overcome regulator spring pressure, open fuel tank return passage and lower fuel pressure. Idle pressure will vary somewhat depending on barometric pressure, however, the pressure idling should be less, indicating proper pressure regulator control.
3. Pressure that continues to fall is caused by one of the following conditions: In-tank fuel pump check valve not holding. Pump coupling hose or pulsator leaking. Fuel pressure regulator valve leaking. Injector(s) sticking open.
4. Check for an injector sticking open by checking for a fouled or saturated spark plug. If a leaking injector can not be determined by a fouled or saturated spark plug, remove plenum, cold start valve and fuel rail bolts. Reconnect cold start valve. Connect a hose to valve nozzle and insert into a gasoline container. Lift fuel rail out just enough to leave injector nozzles in the ports. Turn key on to pressurize fuel system. DO NOT start engine. Lift each side of rail up and check for injector leaking.

Chart A7: Fuel System Schematic. Scheme 307

Chart A7: Fuel Sys Diagnosis Flow Chart (1 of 2). Scheme 308

Fuel System Diagnosis (1 of 3). Scheme 309

Fuel System Diagnosis (2 of 3). Scheme 310

CHART A7: FUEL SYSTEM DIAGNOSIS (2 of 2)

Note. Test numbers refer to test numbers on diagnostic chart.

1. If fuel pressure is less than 40.5 psi (2.8 kg/cm 2 ) check the following: Regulated Pressure Less Than 40.5 psi (2.8 kg/cm 2 ) Amount of fuel to injectors okay, but pressure is too low. Fuel system will be running lean and may set Code 44. Also, vehicle is hard starting cold and has overall poor performance. Restricted Fuel Flow Causing Pressure Drop Normally a vehicle with a fuel pressure of less than 24 psi (1.6 kg/cm 2 ) at idle will not be driveable, however, if the pressure drop occurs only while driving, the engine will normally surge then stop as pressure begins to drop rapidly.
2. Gradually restricting the fuel return line allows the fuel pump to develop pressure. When battery voltage is applied to the pump test terminal or fuel pump relay, pressure should be greater than 47 psi (3.3 kg/cm 2 ).
3. This test determines if the high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.

Chart A7: Fuel System Diagnosis Flow Chart (2 of 2). Scheme 311

Fuel System Diagnosis (3 of 3). Scheme 312

CHART A9: COLD START VALVE (2.8L F BODY)

The cold start valve is used to provide additional fuel during the crank mode to improve cold starts. This circuit is necessary because when engine coolant temperature is low, injector pulse width is not long enough to provide the needed amount of fuel for cold start.

This circuit is completely independent of the ECM. The circuit is activated only in the crank mode. The power is supplied directly from the starter solenoid and is protected by a fuse. The system is controlled by a cold start thermo time switch which provides a ground path for the valve during cranking when engine coolant is less than 95°F (35°C).

The cold start thermo time switch consist of a bi-metallic contact which opens at a specified coolant temperature. This bi-metallic switch is also heated by the circuit winding in the switch. This allows the valve to energize for a maximum of 8 seconds even at coolant temperatures as low as -4°F (-20°C). The time the switch will stay closed (1-8 seconds) varies with coolant temperature. In other words, as the coolant temperature goes up, the cold start valve "on" time goes down.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Disconnecting the distributor 4-way connector will disable the other injectors. The amount of pressure drop depends on the temperature of the engine.
2. This test will determine the resistance through the switch to ground.

Chart A9: Cold Start Valve Schematic (2.8L F Body). Scheme 313

Chart A9: Cold Start Valve Flow Chart. Scheme 314

Cold Start Valve (2.8L F Body 1 of 2). Scheme 315

COLD START VALVE (2.8L F BODY 2 Of 2). Scheme 316

Scheme 317

Scheme 318

Scheme 319

Wiring Diagram (F Body 2.8L VIN S). Scheme 320