How the system works
Follow energy, material, information, and mechanical force through the system before focusing on a single component.
A high-level system map. Component roles and exact circuit behavior vary by vehicle.
- 01InputAir and fuel enter
- 02Flow 2Compression and ignition create combustion
- 03Flow 3Mechanical parts convert pressure into rotation
- 04Flow 4Sensors and controls correct operation
- 05Protect / verifyLubrication and cooling protect the assembly
Follow the sequence, stop when evidence changes the path, and verify the exact vehicle information before acting.
- 01Air and fuel enter
- 02Compression and ignition create combustion
- 03Mechanical parts convert pressure into rotation
- 04Sensors and controls correct operation
- 05Lubrication and cooling protect the assembly
Major components in context
Creates the ignition gap in a spark-ignition engine
Open component →Ignition coilRaises voltage for the spark event
Open component →Fuel injectorMeters fuel when commanded
Open component →MAF sensorReports measured intake airflow on systems that use one
Open component →Seals, compresses, times, and converts combustion force
System contextSymptom patterns and first direction
Cranks but will not start
Separate ignition, fuel, compression, timing, and authorization evidence.
Follow the diagnostic path →SYMPTOMRough idle or shaking
Decide whether combustion is uneven or vibration is being transmitted mechanically.
Follow the diagnostic path →SYMPTOMMisfire code or flashing warning
Reduce load and diagnose promptly; a code identifies detection, not the failed part.
Follow the diagnostic path →SYMPTOMOil leak or oil loss
Locate the fluid and protect the engine before separating external leakage from consumption or another fluid.
Follow the diagnostic path →A system-level diagnostic method
Record operating conditions and warning behavior
Use the result to support or reject a cause group before moving to a more invasive test.
Scan every relevant module before clearing evidence
Use the result to support or reject a cause group before moving to a more invasive test.
Compare related data rather than judging one value alone
Use the result to support or reject a cause group before moving to a more invasive test.
Choose the least invasive test that can reject a cause group
Use the result to support or reject a cause group before moving to a more invasive test.
Verify the repair under the original conditions
Use the result to support or reject a cause group before moving to a more invasive test.
Evidence worth preserving
Freeze-frame and fault context
Cylinder contribution or misfire pattern
Air, fuel, and ignition test results
Compression or mechanical timing evidence when justified
Use the VIN, installed equipment, current manufacturer information, and applicable safety rules.
Safety and professional boundary
Heat and moving-part hazards
Keep hands, clothing, leads, and tools clear of belts, fans, and other moving parts. Exhaust and cooling components can remain hot after shutdown.