ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsMedium
A vehicle's engine cranks slowly but does not start. The headlights dim significantly when attempting to crank the engine. A fully charged battery tests good. Which of the following is the MOST likely cause?
- AExcessive resistance in the starter motor circuit
- BA faulty spark plug or ignition coil
- CA misadjusted idle air control (IAC) valve
- DA restricted fuel filter
Show answer & explanationAnswer & explanation
Correct answer: A. Excessive resistance in the starter motor circuit
Slow cranking and significant dimming of lights under load, despite a good battery, indicate that a large amount of current is being drawn, but not effectively reaching the starter, or the starter itself is struggling. This points to excessive resistance in the starter motor circuit, which can be caused by corroded cables or a failing starter.
Why the other options are wrong
- B. Faulty spark plugs or ignition coils would prevent starting but not cause slow cranking or headlight dimming during cranking.
- C. A misadjusted IAC valve affects idle speed but would not cause slow cranking or headlight dimming.
- D. A restricted fuel filter would prevent starting but not cause slow cranking or headlight dimming during cranking.
Slow Cranking Diagnosis
Slow cranking with headlight dimming, despite a good battery, indicates high resistance in the starter circuit or a struggling starter motor, leading to excessive current draw and voltage drop.
- Good battery ruled out.
- Headlight dimming points to high current draw.
- Focus on starter circuit components.
Memory trick: Cranking Slow? Check the Flow!