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2020 Ram 2500 Cummins - Cranks but No Start

0

Mike T. · rep 0 · May 25, 2:26 AM · 1 replies · solved · Question

Vehicle: 2020 Ram 2500 Laramie

My 2020 Ram 2500 Laramie with the 6.7L Cummins diesel is giving me a headache. This morning, it just cranks and cranks but won't fire up. No Check Engine Light is on, and I don't hear the fuel pump priming like I usually do. The battery seems strong, as it's cranking vigorously.

I tried cycling the key a few times, but still nothing. I'm worried it might be something serious. Any ideas on what I should check first? It was running perfectly fine yesterday.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:26 AM

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ClearTheCode admin answer:

  1. Understanding a Crank-No-Start Condition (Diesel): For a diesel engine to start, it primarily needs fuel, compression, and a signal to inject the fuel at the right time. Unlike gasoline engines, spark isn't a factor. Your observation about not hearing the fuel pump is a critical clue.

  2. Initial Diagnostic Steps:

    • Check Fuel System: The lack of a priming sound suggests an issue with the fuel delivery. Check the fuel filter for clogging or water contamination (especially important for diesels). Ensure there's fuel in the tank. Locate the fuel pump relay in the fuse box and check if it's functioning; you can try swapping it with a known good relay of the same type.
    • Inspect Fuel Lines and Connections: Look for any visible leaks or damage in the fuel lines. Ensure all connections are secure.
    • Battery Voltage & Connections: Even if it cranks, low voltage can prevent critical modules from powering up correctly. Check battery terminals for corrosion and ensure they are tight. A weak battery might crank but not provide enough voltage for the ECM/PCM to function properly.
    • Crankshaft Position Sensor: A faulty crankshaft position sensor can prevent the engine from knowing when to inject fuel, leading to a no-start condition, often without a CEL.

  3. Common Causes for Diesel No-Start:

    • Clogged fuel filter or water in fuel.
    • Failing fuel pump (lift pump or high-pressure pump).
    • Faulty fuel pump relay or fuse.
    • Air in the fuel system (can happen after filter changes if not bled properly).
    • Bad crankshaft position sensor or camshaft position sensor.
    • Low fuel pressure due to a leak or regulator issue.

  4. When to See a Professional Shop:

    • If you've checked the basic fuel system components and battery, and the issue persists.
    • If you suspect a high-pressure fuel pump issue, as this requires specialized diagnostic tools and expertise.
    • If the issue points to sensor failure (crankshaft/camshaft position) that you're not comfortable replacing.
    • Any time you're dealing with complex diesel fuel systems, professional diagnosis is often the safest and most efficient route.
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