Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsGeneral Electrical/Electronic System DiagnosisMedium
A technician is diagnosing a vehicle with an intermittent no-start condition. The technician observes that the engine cranks normally but does not fire. Using a scan tool, the technician notes that the fuel pressure sensor reads 0 PSI during cranking. What is the MOST likely cause of this symptom?
- AA short to ground in the fuel injector circuit
- BAn open in the fuel pump power circuit
- CA faulty crankshaft position sensor signal
- DA clogged fuel filter
Show answer & explanationAnswer & explanation
Correct answer: B. An open in the fuel pump power circuit
A fuel pressure reading of 0 PSI during cranking indicates no fuel delivery to the engine. While a clogged filter could reduce pressure, an open circuit in the fuel pump power supply would completely prevent the pump from operating, leading to 0 PSI.
Why the other options are wrong
- A. A short to ground in the fuel injector circuit would affect fuel delivery but would not directly cause 0 PSI at the fuel pressure sensor, as the pump would still be attempting to build pressure.
- C. A faulty crankshaft position sensor would typically prevent cranking or spark, not specifically indicate 0 PSI fuel pressure while cranking.
- D. A clogged fuel filter would reduce fuel pressure but typically not to 0 PSI during cranking, as some residual pressure or pump effort would still be present.
Fuel Pump Power Circuit
The electrical path that supplies voltage and ground to the fuel pump, enabling it to deliver fuel to the engine.
- Crucial for fuel delivery
- Includes fuse, relay, wiring, and pump motor
- An open circuit prevents pump operation
Memory trick: Fuel's not flowing, current's not going.