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Separate fuel, spark, compression, timing, and security-system faults with a test-first process.
IntermediateUse the first starting split—cranks or does not crank—to choose the correct electrical, authorization, fuel, ignition, or mechanical diagnostic path.
beginnerSeparate a missing lamp or changed circuit load from socket, wiring, switch, module, hazard, and control evidence before replacing a flasher or lamp.
beginnerSeparate missing ignition, fuel delivery, control, synchronization, and mechanical evidence after the engine is confirmed to crank.
Test-first procedureUse warning behavior, scan context, cylinder pattern, and controlled contribution evidence to separate ignition, fuel, air, and mechanical branches.
Test-first procedureThe starting system must authorize the request and deliver high current long enough to rotate the engine. A no-crank condition is different from an engine that cranks normally but does not run.
System guideThe fuel system stores and meters fuel under controlled conditions. A no-start, lean code, odor, or hesitation can involve supply, command, air measurement, electrical control, mechanical condition, or vapor management.
System guideThe engine turns stored fuel energy into controlled torque. Good diagnosis separates a combustion problem from a mechanical, control, mounting, or support-system problem before parts are removed.
System guideAI guidance is separate from verified IAR sources.
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