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2020 Wrangler JL 3.6L No Start - Cranks but Won't Catch

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Mike T. · rep 0 · May 25, 2:20 AM · 1 replies · solved · Question

Vehicle: 2020 Jeep Wrangler JL Sahara

Hey everyone, hoping someone can help me out here. My 2020 Jeep Wrangler JL Sahara (3.6L Pentastar) suddenly won't start. It cranks strongly, sounds like it's trying, but it just won't catch and fire up. It was running perfectly fine yesterday.

I've checked the battery, and it seems good – plenty of juice for cranking. I don't have any immediate check engine lights, but I haven't tried scanning for pending codes yet. Could this be a fuel pump issue, or maybe something with the ignition system? I'm stranded at home and need to figure this out soon.

Any ideas on what I should check first? Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:20 AM

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ClearTheCode admin answer:

A "cranks but no start" condition on your 2020 Jeep Wrangler JL 3.6L can be frustrating. This usually points to a problem with one of the three main components required for combustion: fuel, spark, or air. Since it cranks strongly, we can likely rule out a completely dead battery or starter motor.

Common Causes for Cranks-No-Start:

  1. Fuel Delivery Issues:
    • Low Fuel Pressure: A failing fuel pump, clogged fuel filter, or a faulty fuel pressure regulator can prevent adequate fuel from reaching the engine.
    • No Fuel: While obvious, ensure you actually have fuel in the tank, and the gauge isn't faulty.
  2. Ignition System Problems:
    • Faulty Spark Plugs/Coils: Worn spark plugs or failing ignition coils can prevent proper spark.
    • Crankshaft Position Sensor (CKP) or Camshaft Position Sensor (CMP) Failure: These sensors tell the engine computer when to fire the spark plugs and inject fuel. A bad sensor can lead to a no-start condition without necessarily throwing a CEL immediately.
  3. Air/Compression Issues:
    • Major Vacuum Leak: Less common for a sudden no-start, but a severe leak could impact air intake.
    • Blocked Air Intake: A completely clogged air filter or obstruction.

Troubleshooting Steps:

  1. Check for Fuel Pressure: When you turn the key to the "ON" position (without cranking), listen for a faint hum from the rear of the vehicle. This is the fuel pump priming. If you don't hear it, the pump might be failing.
  2. Spray Starting Fluid (Caution!): Briefly spray a small amount of starting fluid into the air intake (after the air filter). If the engine briefly sputters or starts, it indicates a fuel delivery problem.
  3. Scan for Codes: Even without a CEL, use an OBD-II scanner to check for any pending or stored codes. Codes like P0335 (CKP sensor) or P0340 (CMP sensor) would be very relevant.
  4. Check Fuses: Inspect the fuel pump fuse and any ignition-related fuses in both the under-hood and cabin fuse boxes.

When to See a Shop:

  • If you've confirmed fuel and spark are present but it still won't start.
  • If you're uncomfortable performing the checks yourself.
  • If the issue points to a fuel pump, CKP/CMP sensor, or more complex electrical diagnosis. These often require specialized tools and expertise for proper replacement and diagnosis.
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