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2020 Ram 2500 6.4L Hemi No Start - Cranks but Won't Catch

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Ashley M. · rep 0 · May 22, 3:30 AM · 1 replies · solved · Question

Vehicle: 2020 Ram 2500 Tradesman 6.4L Hemi

Hello Ram community, I'm having a major issue with my 2020 Ram 2500 Tradesman, equipped with the 6.4L Hemi. This morning, it just cranks and cranks but won't start. It sounds like it's trying, but it never actually fires up.

I've checked the battery, and it seems strong enough to crank the engine vigorously. I don't hear the fuel pump prime when I turn the key to ON, which is concerning. I also tried cycling the key a few times, but no luck. There are no warning lights on the dash other than the usual ones that come on when the key is in the ON position.

Any ideas on what could be causing this? Could it be a fuel pump issue, a sensor, or something else entirely? I'm stranded and need some guidance.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:30 AM

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ClearTheCode admin answer:

A 'crank but no start' condition on your 2020 Ram 2500 6.4L Hemi typically points to a lack of one of the three critical elements for combustion: fuel, spark, or air (compression is less likely to suddenly fail across all cylinders). Since you mentioned not hearing the fuel pump prime, that's a significant clue.

Here's a systematic approach to diagnose the issue:

  1. Check for Fuel Delivery:

    • Cause: The most common reason for a 'no prime' sound is a faulty fuel pump, a blown fuel pump fuse, a bad fuel pump relay, or an issue with the fuel pump control module.
    • Action:
      1. Listen for Pump: Have someone turn the key to the 'ON' position (not start) while you listen near the fuel tank for a faint whirring sound. If you hear nothing, proceed.
      2. Check Fuses/Relays: Locate the fuel pump fuse and relay in your truck's fuse box (refer to your owner's manual). Check the fuse for continuity and swap the relay with a known good one (e.g., horn relay if it's the same type) to see if that resolves the issue.
      3. Fuel Pressure Test: If you have access to a fuel pressure gauge, connect it to the Schrader valve on the fuel rail. You should see appropriate fuel pressure (check your service manual for exact specs, typically 50-60 psi for a Hemi) when the key is turned to 'ON' and while cranking.

  2. Check for Spark:

    • Cause: A lack of spark can be due to a faulty crankshaft position sensor, camshaft position sensor, ignition coils, or even a problem with the PCM (Powertrain Control Module).
    • Action: While cranking, use an inline spark tester on one of the spark plug wires (or coil-on-plug if applicable) to confirm spark. If no spark, check for codes, as a bad crank sensor often prevents spark and fuel.

  3. Check for Air/Compression:

    • Cause: While less common for a sudden no-start, a severely restricted air intake or major internal engine damage could prevent starting.
    • Action: Ensure the air filter isn't completely clogged. If you have a scan tool, check for any codes related to engine timing or sensor failures.

When to See a Shop: Given your observation about the fuel pump not priming, start with checking the fuel pump fuse and relay. If those are good and you still have no fuel pressure, or if you're unable to perform these checks, it's time to call for a tow to a qualified mechanic. A professional can quickly diagnose fuel system issues, sensor failures, or other complex electrical problems that prevent your truck from starting.

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