Engine Controls - Basic Testing: Diagnosis Chevrolet Metro I

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 not pinched or cut. See appropriate VACUUM DIAGRAMS article to verify routing and connections. Inspect air induction system for possible vacuum leaks.

Diagnosis

1. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000-2500 RPM and note gauge. If reading exceeds 1.25 psi (.09 kg/cm 2 ), exhaust system is restricted.
2. Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exist, check for restricted catalytic converter. Replace as necessary.

NO START DIAGNOSIS

Note. For terminal and circuit identification, see appropriate wiring diagram in WIRING DIAGRAMS article.

1. Definition No-start is defined as engine cranks properly, but does not start. Engine may fire a few times.

Diagnostic Aids

Fuel injectors may not spray enough fuel to start engine. Check Engine Coolant Temperature (ECT) sensor. Temperature should be close to actual engine temperature for PCM to deliver correct amount of fuel.

Check Throttle Position (TP) sensor. Voltage reading should be 0.98-1.02 volts with a .140" (3.5 mm) feeler gauge placed between throttle stop screw and throttle lever.

Check battery condition and engine cranking speed. Engine will not start if cranking system is not functioning properly.

Water or foreign material in fuel can cause a no-start condition during freezing weather. Engine may start after 5-6 minutes in a heated shop. Problem may not appear until vehicle is parked overnight in freezing temperatures.

A vehicle that starts and runs after an "engine cranks but will not run" complaint, may be susceptible to moisture. Start engine and spray water on ignition system components and wiring in order to check for a miss or engine stall.

Also check the following for a possible cause of fault

1. Low fuel pressure, resulting in an excessively lean air/fuel mixture.
2. Fouled or damaged spark plugs.
3. With no MIL, check for a faulty main relay.
4. Open IG fuse.
5. Check fuel injector resistor connections and resistance. Resistor resistance should be 1.9-2.8 ohms at 68°F (20°C).
6. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Check for an open or loose or disconnected terminals.

Fuel injectors may not spray enough fuel to start engine. Check Engine Coolant Temperature (ECT) sensor. Temperature should be close to actual engine temperature for PCM to deliver correct amount of fuel.

Check Throttle Position (TP) sensor. Voltage should be 0.2-1.0 volt with throttle closed.

Check battery condition and engine cranking speed. Engine will not start if cranking system is not functioning properly.

Water or foreign material in fuel can cause a no-start condition during freezing weather. Engine may start after 5-6 minutes in a heated shop. Problem may not appear until vehicle is parked overnight in freezing temperatures.

A vehicle that starts and runs after an "engine cranks but will not run" complaint, may be susceptible to moisture. Start engine and spray water on ignition system components and wiring in order to check for a miss or engine stall.

Also check the following for a possible cause of fault

1. Low fuel pressure, resulting in an excessively lean air/fuel mixture.
2. Fouled or damaged spark plugs.
3. With no MIL, check for a faulty main relay.
4. Open IG fuse.
5. Check fuel injector resistor connections and resistance. Resistor resistance should be 1.9-2.8 ohms at 68°F (20°C).
6. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Check for an open or loose or disconnected terminals.

Fuel injectors may not spray enough fuel to start engine. Check Engine Coolant Temperature (ECT) sensor. Temperature should be close to actual engine temperature for PCM to deliver correct amount of fuel.

Check Throttle Position (TP) sensor. Reading should be 0.3-0.8 volt with throttle closed.

Check battery condition and engine cranking speed. Engine will not start if cranking system is not functioning properly.

Water or foreign material in fuel can cause a no-start condition during freezing weather. Engine may start after 5-6 minutes in a heated shop. Problem may not appear until vehicle is parked overnight in freezing temperatures.

A vehicle that starts and runs after an "engine cranks but will not run" complaint, may be susceptible to moisture. Start engine and spray water on ignition system components and wiring in order to check for a miss or engine stall.

Also check the following for a possible cause of fault

1. Low fuel pressure, resulting in an excessively lean air/fuel mixture.
2. Fouled or damaged spark plugs.
3. With no MIL, check for a faulty main relay.
4. Open IG fuse.
5. Check fuel injector resistor connections and resistance. Resistor resistance should be 1.9-2.8 ohms at 68°F (20°C).
6. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Check for an open or loose or disconnected terminals.