The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2021 Legacy 2.5i Rough Start and Fuel Smell

0

Chris P. · rep 0 · May 25, 2:14 AM · 1 replies · solved · Question

Vehicle: 2021 Subaru Legacy 2.5i Sport

I've got a 2021 Subaru Legacy 2.5i Sport with about 40,000 miles, and lately, I've been noticing a couple of concerning things. First, it sometimes has a rough start, especially after sitting for a few hours. It cranks a bit longer than usual before firing up, and when it does, it feels a little shaky for a few seconds.

Second, I've occasionally caught a faint smell of fuel, particularly after starting the car. It's not constant, but it's enough to make me worried. No check engine light has come on yet, but I'm keeping an eye on it. Any ideas what might be going on?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:14 AM

0

Rough starts and a fuel smell, especially after the vehicle has been sitting, are classic indicators of a potential fuel system issue on your 2021 Subaru Legacy. While no Check Engine Light (CEL) is on yet, these symptoms warrant immediate attention due to the safety risk associated with fuel leaks and potential damage to engine components.

Here are the most likely causes:

  1. Fuel Pressure Leak-Down: If the fuel system isn't holding pressure after the engine is turned off, it takes longer for the fuel pump to re-pressurize the system upon startup, leading to extended cranking and rough starts. This can be caused by:
    • Leaky Fuel Injector(s): An injector that isn't sealing properly can drip fuel into the cylinder or manifold, causing a rich condition on startup and potentially the fuel smell.
    • Faulty Fuel Pump Check Valve: The check valve in the fuel pump assembly is designed to maintain fuel pressure. If it fails, pressure bleeds off.
    • Fuel Pressure Regulator Issue: While less common on newer direct-injection systems, a faulty regulator could contribute.
  2. External Fuel Leak: The fuel smell is a major concern. Even a small leak from a fuel line, O-ring, fuel rail, or the fuel tank/sending unit area could cause this. This is a fire hazard.
  3. Evaporative Emission (EVAP) System Issues: A leak in the EVAP system (e.g., a cracked hose, faulty purge valve, or loose gas cap) could allow fuel vapors to escape, causing the smell. This typically triggers a CEL with codes like P0440, P0442, P0455.

What to do:

  • Immediate Inspection: Visually inspect the engine bay and underneath the car for any signs of fuel leaks (wet spots, drips, strong fuel smell). Pay close attention to the fuel rail, injectors, and fuel lines.
  • Check Gas Cap: Ensure your gas cap is tightened properly. A loose cap can sometimes cause fuel smells and eventually trigger an EVAP code.
  • Professional Diagnosis: A mechanic can perform a fuel pressure test to check for leak-down, inspect the EVAP system, and use a smoke machine to detect subtle fuel vapor leaks.

When to see a shop: You should schedule an appointment immediately. A fuel smell is a serious safety concern due to fire risk. Even without a CEL, these symptoms indicate a problem that could worsen, potentially leading to more severe engine issues or a hazardous situation. Do not delay diagnosis and repair.

Menu

Help & account