ASE G1 Auto Maintenance and Light RepairEngine SystemsHard
A vehicle with an electronic fuel injection system cranks but does not start. A technician confirms there is good spark and engine compression. When checking for fuel, the technician hears the fuel pump prime briefly when the key is turned to the 'ON' position, but no fuel pressure is detected at the fuel rail. What is the most likely cause?
- AA ruptured fuel line inside the tank
- BA faulty fuel pressure regulator
- CA clogged fuel filter
- DA stuck-open fuel injector
Show answer & explanationAnswer & explanation
Correct answer: A. A ruptured fuel line inside the tank
If the fuel pump primes (indicating it's receiving power and attempting to work) but no pressure reaches the fuel rail, a ruptured fuel line inside the tank or a significant leak in the in-tank pump assembly is the most probable cause, as the pump is running but not building effective pressure in the delivery system.
Why the other options are wrong
- B. A faulty fuel pressure regulator would typically result in incorrect pressure (too high or too low), but not zero pressure if the pump is priming and there are no other major leaks.
- C. A clogged fuel filter would likely cause some pressure, but restricted flow, or no start under load, not zero pressure with a priming pump.
- D. A stuck-open fuel injector would cause a rich condition, misfires, or hydro-lock, but wouldn't prevent fuel pressure from building at the rail if the pump is working.
No Fuel Pressure (Pump Primes)
If a fuel pump primes but no fuel pressure is detected at the rail, it often indicates a significant leak or rupture within the fuel tank itself, preventing pressure from building in the fuel delivery lines.
- Pump priming means it gets power.
- No pressure with priming indicates an internal leak.
- Ruptured in-tank line is a common culprit.
Memory trick: Pump hums, no pressure, in-tank rupture is the stressor.