ASE A1 Engine RepairGeneral Engine DiagnosisMedium
A technician observes that a vehicle's engine requires excessive cranking time before starting, especially after sitting overnight. Once started, it runs smoothly. There are no fault codes. Which of the following is the most likely cause?
- AA restricted exhaust system
- BA weak battery
- CLeaking fuel injectors
- DA faulty crankshaft position sensor
Show answer & explanationAnswer & explanation
Correct answer: C. Leaking fuel injectors
Leaking fuel injectors can cause a loss of fuel pressure overnight, requiring extended cranking to re-pressurize the system and deliver adequate fuel for starting. Once pressure is built, the engine runs normally.
Why the other options are wrong
- A. A restricted exhaust system would cause poor performance and lack of power once running, not just hard starting after sitting.
- B. A weak battery would cause slow cranking, not necessarily extended cranking time followed by a smooth start, and often struggles more when hot.
- D. A faulty crankshaft position sensor would likely prevent the engine from starting at all or cause erratic running, and often set a fault code.
Hard Start (Extended Crank)
Extended cranking time before an engine starts, particularly after a period of rest, often points to a loss of fuel pressure or an issue with fuel delivery.
- Commonly due to fuel system issues
- Loss of fuel pressure is a frequent culprit
- Can be caused by leaking injectors or a failing fuel pump check valve
Memory trick: Long crank, no codes? Think 'Fuel Pressure Leak'!