ASE G1 Auto Maintenance and Light RepairEngine SystemsMedium
A technician is diagnosing a vehicle that cranks but does not start. They confirm that there is adequate fuel pressure at the fuel rail and spark at the spark plugs. Which of the following components should the technician investigate next?
- AEngine coolant temperature (ECT) sensor
- BMass air flow (MAF) sensor
- COxygen (O2) sensor
- DFuel injector circuit
Show answer & explanationAnswer & explanation
Correct answer: D. Fuel injector circuit
With confirmed fuel pressure and spark, the next logical step is to check if the fuel is actually entering the combustion chambers. The fuel injectors are responsible for atomizing and spraying fuel, so their circuit should be investigated.
Why the other options are wrong
- A. The ECT sensor primarily affects fuel mixture and timing after the engine starts, not typically a no-start condition if spark and fuel pressure are present.
- B. A faulty MAF sensor can cause starting issues, but typically not if both spark and fuel pressure are confirmed. Injector issues are more direct for a no-start with these conditions met.
- C. The O2 sensor provides feedback for fuel trim after the engine is running and warmed up, not for initial starting.
No-Start Condition Diagnosis
A systematic approach to identify the cause when an engine cranks but fails to start, focusing on the three essential elements: spark, fuel, and compression.
- Always verify all three elements (spark, fuel, compression).
- Address the most common failures first.
- Use a diagnostic flow chart or systematic approach.
Memory trick: Spark, Fuel, Air, Compression - Make the engine start with a 'S.F.A.C.'!