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2016 E350 Cranks But Won't Start - No Fuel Pressure?

0

Mike T. · rep 0 · May 25, 3:04 AM · 1 replies · solved · Question

Vehicle: 2016 Mercedes-Benz E350 W212

My 2016 Mercedes-Benz E350 (W212) has suddenly developed a major issue: it cranks strongly but refuses to start. It just turns over and over without catching. This happened out of the blue this morning.

I've checked the battery, and it seems fine – the starter motor sounds strong. I'm suspecting a fuel delivery problem. I don't hear the fuel pump priming when I unlock the car or turn the ignition on, which is unusual. Could this be a fuel pump relay, the pump itself, or something else entirely?

Are there any common issues with the fuel system on these E-Class models that could cause a complete no-start condition? I'm stranded and trying to figure out if it's something I can quickly check.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:04 AM

0

ClearTheCode admin answer:

A 'cranks but no start' condition on your 2016 Mercedes-Benz E350 is frustrating and typically points to an issue with one of the three essentials for engine combustion: fuel, spark, or air. Given your observation about not hearing the fuel pump, a fuel delivery problem is a strong candidate.

Here's how to approach the diagnosis:

  1. Common Causes for No-Start (Cranks But No Catch):

    • Fuel System Failure: This includes a faulty fuel pump, clogged fuel filter, bad fuel pump relay, or a problem with the fuel pressure regulator.
    • Ignition System Issues: Faulty crank position sensor, camshaft position sensor, bad spark plugs, or ignition coils (though less likely to cause a complete no-start across all cylinders simultaneously).
    • Immobilizer System: A fault in the vehicle's anti-theft system can prevent the engine from starting.
    • Engine Control Unit (ECU) Failure: Rare, but possible.

  2. Diagnostic Steps:

    • Check for Fuel Pump Operation: Have someone listen near the fuel tank (usually under the rear seat or in the trunk area) while you turn the ignition to the 'on' position (without cranking). A faint hum indicates the pump is priming. If no hum, check the fuel pump fuse and relay. The fuse box diagram should be in your owner's manual or on the fuse box cover.
    • Fuel Pressure Test: If you have access to a fuel pressure gauge, connect it to the Schrader valve on the fuel rail (if present) to confirm actual fuel pressure. A healthy system should show around 55-75 PSI.
    • Check for OBD-II Codes: Even without a Check Engine Light, a pending or stored code might indicate a fault with the crank position sensor (very common for no-start), camshaft position sensor, or immobilizer.
    • Spark Test: If you suspect fuel is okay, carefully remove a spark plug wire/coil and test for spark using a spark tester. This requires caution.

  3. When to See a Shop:

    • If you confirm there's no fuel pump operation, and the fuse/relay are good, the fuel pump itself is likely the culprit, and replacement is best left to a professional.
    • If you get no spark, or if you find no relevant OBD-II codes but the car still won't start, a professional diagnostic is essential. They have specialized tools to test sensors, the immobilizer system, and fuel system components safely and accurately.
    • Diagnosing a no-start condition can be complex, and incorrect troubleshooting can lead to further issues. For a critical component like a fuel pump, professional installation ensures safety and correct function.
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