VISUAL INSPECTION
Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. See VACUUM DIAGRAMS article in this section to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.
MECHANICAL INSPECTION
| CAUTION | DO NOT use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine. Fuel injectors on many models are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate engine oiling system. |
DIAGNOSTIC CHARTS - EXCEPT LSi
Note. The following Schematics and Flow Charts are Courtesy of General Motors Corp.
Diagnostic Aids
Water or foreign material in fuel can cause a no-start or a lack of power condition. Low fuel pressure, a restricted fuel filter or fuel injectors may cause a no-start condition. See CHART A1-5 for fuel injector circuit test.
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before replacing components.
Chart A1-3 Schematic - Except LSi Engine Cranks But Will Not Run. Scheme 1
Chart A1-3 Flow Chart - Except LSi Engine Cranks But Will Not Run. Scheme 2
Fuel spray may exist at fuel injectors, but it may not be enough to start engine. If fuel injectors and their circuits are okay, and fuel spray is detected, fuel injector nozzle may be partly blocked or restricted. See CHART A1-7A for circuit opening relay check.
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before replacing components.
Chart A1-5 Schematic - Except LSi Fuel Injector Circuit Check - Engine No-Start. Scheme 3
Chart A1-5 Flow Chart - Except LSi Fuel Injector Circuit Check - Engine No-Start. Scheme 4
CHART A1-7A, FUEL SYSTEM DIAGNOSIS (CIRCUIT OPENING RELAY CHECK)
When ignition switch is in START position, circuit opening relay will be energized to allow fuel pump to operate to pressurize system. Fuel pump will continue to operate if ECM receives an ignition signal when engine starts. Fuel pump operates as long as circuit opening relay is energized by ECM. When circuit opening relay is de-energized, fuel pump will stop operating.
Note. Test numbers refer to numbers on diagnostic chart.
- Checks for normal fuel pump operation.
- Checks if fuel pump will run when DLC terminals B+ and FP are jumpered together.
- Checks fuel pump operation while ignition signal is present at ECM.
- Checks for an open in Black/Red wire to circuit opening relay.
- Checks for an open in Black/Red wire to DLC.
- Checks for an open Blue/Black or Green/Red wire, a faulty ECM, or a faulty circuit opening relay.
- Checks for open White/Black or Blue/Black wire, or faulty fuel pump.
A restricted or leaking fuel feed pipe or hose will cause an "engine cranks but will not run" condition. Check fuel sender assembly connections inside fuel tank for poor connection. See CHART A1-7B for fuel pressure test.
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before replacing components.
Chart A1-7A Schematic - Except LSi Fuel System Diagnosis - Circuit Opening Relay Check. Scheme 5
Chart A1-7A Flow Chart - Except LSi Fuel System Diagnosis - Circuit Opening Relay Check - 1 of 2. Scheme 6
Chart A1-7A Flow Chart - Except LSi Fuel System Diagnosis - Circuit Opening Relay Check - 2 of 2. Scheme 7
CHART A1-7B, FUEL SYSTEM DIAGNOSIS (FUEL PRESSURE CHECK)
When ignition switch is turned to START position, circuit opening relay will be energized to allow fuel pump to operate to pressurize system. Fuel pump will continue to operate if ECM receives an ignition signal when engine starts. Fuel pump operates as long as circuit opening relay is energized by ECM. When circuit opening relay is de-energized, fuel pump will stop operating. Fuel pump delivers fuel to fuel rail where pressure is maintained by fuel pressure regulator at 41 psi (282.7 kPa) more than pressure inside intake manifold. Excess fuel is returned to fuel tank through a return pipe and hoses.
Note. Test numbers refer to numbers on diagnostic chart.
- Measures fuel pressure with ignition switch in ON position.
- Determines if fuel pressure is normal.
- Checks for leaking fuel pressure regulator.
- Checks for plugged fuel injectors.
- Checks for leaking fuel injectors or a leaking fuel pump.
- Checks for a leaking fuel pressure regulator or fuel pump
Check for leakage around all fuel hose/pipe connections. A plugged fuel injector could be the cause of a hard/no-start condition or loss of power/poor fuel economy. See appropriate TESTS W/O CODES article for mechanical checks and inspections if fuel spray and pressure is normal.
Chart A1-7B Schematic - Except LSi Fuel System Diagnosis - Fuel Pressure Check. Scheme 8
Chart A1-7B Flow Chart - Except LSi Fuel System Diagnosis - Fuel Pressure Check - 1 of 2. Scheme 9
Chart A1-7B Flow Chart - Except LSi Fuel System Diagnosis - Fuel Pressure Check - 2 of 2. Scheme 10
DIAGNOSTIC CHARTS - LSi
Note. The Following Schematics and Flow Charts are Courtesy of General Motors Corp.
Water or foreign material in fuel can cause no-start or lack of power condition. Low fuel pressure or restricted fuel filter or injectors may cause no-start condition. Refer to CHART A2-5 for fuel injector circuit test.
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before replacing. components
Chart A2-3 Schematic - LSi Engine Cranks But Will Not Run. Scheme 11
Chart A2-3 Flow Chart - LSi Engine Cranks But Will Not Run. Scheme 12
Fuel spray may exist at fuel injectors, but it may not be enough to start engine. If fuel injectors and their circuit are okay, and fuel spray is detected, fuel injector nozzle may be partly blocked or restricted. See CHART A2-7A for circuit opening relay check.
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before replacing components.
Chart A2-5 Schematic - LSi Fuel Injector Circuit Check - Engine No-Start. Scheme 13
Chart A2-5 Flow Chart - LSi Fuel Injector Circuit Check - Engine No-Start. Scheme 14
CHART A2-7A, FUEL SYSTEM DIAGNOSIS (CIRCUIT OPENING RELAY CHECK)
When ignition switch is turned to START position, circuit opening relay will be energized to allow fuel pump to operate to pressurize system. Fuel pump will continue to operate if PCM receives an ignition signal when engine starts. Fuel pump operates as long as circuit opening relay is energized by PCM. When circuit opening relay is de-energized, fuel pump will stop operating.
Note. Test numbers refer to numbers on diagnostic chart.
- Checks for normal fuel pump operation.
- Checks if fuel pump will run when DLC terminals B+ and FP are jumpered together.
- Checks fuel pump operation while ignition signal is present at PCM.
- Checks for an open in Black/Red wire to circuit opening relay.
- Checks for an open in Black/Red wire to DLC.
- Checks for an open Blue/Black or Green/Red wire, a faulty PCM, or a faulty circuit opening relay.
- Checks for open White/Black or Blue/Black wire, or faulty fuel pump.
A restricted or leaking fuel feed pipe or hose will cause an "engine cranks but will not run" condition. Check fuel sender assembly connections inside fuel tank for poor connection. See CHART A2-7B for fuel system pressure test.
An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before replacing components.
Chart A2-7A Schematic - LSi Fuel System Diagnosis - Circuit Opening Relay Check. Scheme 15
Chart A2-7A Flow Chart - LSi Fuel System Diagnosis - Circuit Opening Relay Check - 1 of 2. Scheme 16
Chart A2-7A Flow Chart - LSi Fuel System Diagnosis - Circuit Opening Relay Check - 2 of 2. Scheme 17
CHART A2-7B, FUEL SYSTEM DIAGNOSIS (FUEL PRESSURE CHECK)
When ignition switch is in ON or START position, circuit opening relay will be energized to allow fuel pump to operate to pressurize system. Fuel pump will continue to operate if PCM receives an ignition signal when engine is started. Fuel pump operates as long as circuit opening relay is energized by PCM. When circuit opening relay is de-energized, fuel pump will stop operating. Fuel pump delivers fuel to fuel rail where pressure is maintained by fuel pressure regulator at 41 psi (282.7 kPa) more than pressure inside intake manifold. Excess fuel is returned to fuel tank through a return pipe and hoses.
Note. Test numbers refer to numbers on diagnostic chart.
- Measures fuel pressure with ignition switch in ON position.
- Determines if fuel pressure is normal.
- Checks for a leaking fuel pressure regulator.
- Checks for plugged fuel injectors.
- Checks for leaking fuel injectors or a leaking fuel pump.
- Checks for a leaking fuel pressure regulator or fuel pump
Check for leakage around all fuel hose/pipe connections. A plugged fuel injector could be the cause of a hard/no-start condition or loss of power/poor fuel economy. Refer to TESTS W/O CODES article for mechanical checks and inspections if fuel spray and pressure is normal.
