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2020 Mazda 3 Cranks But Won't Start Intermittently

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David L. · rep 0 · May 22, 4:48 AM · 1 replies · solved · Question

Vehicle: 2020 Mazda 3 Preferred

I'm having a really frustrating issue with my 2020 Mazda 3 Preferred. Lately, it's been cranking strongly, but just won't fire up on the first try. Sometimes it takes 3-4 attempts of cranking before it finally catches and starts like normal. Other times, it starts right away without any hesitation.

There's no check engine light on, and once it starts, it runs perfectly fine. This problem seems to be completely random, happening both when the engine is cold and when it's warm. I've checked the battery, and it seems strong.

Could this be a fuel pump issue, a problem with the ignition system, or something else entirely? It's becoming a real hassle, especially when I'm in a hurry. Any ideas on what I should investigate first?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:48 AM

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ClearTheCode admin answer:

An intermittent crank-no-start condition, especially without a check engine light, can be tricky to diagnose. Since your engine cranks strongly, we can likely rule out a completely dead battery or starter motor. The issue likely lies in one of the three main components required for combustion: fuel, spark, or air.

Here are the common areas to investigate:

  1. Fuel Delivery System:
    • Fuel Pump: The fuel pump might be intermittently failing to build sufficient pressure, or the fuel pressure regulator could be faulty. Listen for the fuel pump priming sound (a low hum from the rear of the car) when you turn the key to the 'ON' position (before cranking).
    • Fuel Filter: A clogged fuel filter could restrict fuel flow, especially during initial startup.
    • Fuel Injectors: One or more injectors could be sticking or not opening properly, leading to insufficient fuel delivery.
  2. Ignition System:
    • Spark Plugs/Coils: While less likely to be intermittent without a misfire code, a weak spark could cause hard starting. However, if it runs fine once started, this is less probable.
    • Crankshaft Position Sensor: A failing crankshaft position sensor can cause intermittent no-start conditions by not sending the correct signal to the ECU for spark and fuel timing. This often doesn't immediately trigger a CEL.
  3. Air Intake:
    • Mass Airflow (MAF) Sensor: A dirty or faulty MAF sensor can send incorrect air readings, affecting the fuel-air mixture. However, this usually causes driveability issues and often a CEL.
  4. Immobilizer System: Rarely, an intermittent fault in the vehicle's immobilizer system (key chip, antenna ring) can prevent starting. Try using a spare key if you have one.

When to see a shop:

  • If you can't identify the issue after basic checks (listening for fuel pump, checking battery terminals).
  • If you suspect a fuel pressure issue, as this requires specialized tools to test safely.
  • If the problem becomes more frequent or consistent, or if a check engine light eventually illuminates. A professional diagnostic scan can often reveal pending codes or live data anomalies that point to the root cause.
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