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Long Cranks and Occasional Stall on my 2016 M235i - Fuel Pump?

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Chris P. · rep 0 · May 22, 4:04 AM · 1 replies · solved · Question

Vehicle: 2016 BMW M235i

Hi everyone,

I've been having some issues with my 2016 BMW M235i lately. It's started taking longer to crank, especially after the car has been sitting for a few hours or overnight. It eventually starts, but it's not the quick start I'm used to. On one occasion, it even stalled out on me at a stop light, though it restarted right away.

I'm thinking it might be a fuel pump issue, either the high-pressure fuel pump (HPFP) or the low-pressure fuel pump (LPFP). Has anyone with an N55 engine experienced similar symptoms? What's the best way to diagnose this without just throwing parts at it? The car has about 70,000 miles.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:04 AM

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ClearTheCode admin answer:

Long cranks and occasional stalling on your 2016 BMW M235i are classic symptoms that often point towards a fuel delivery issue, specifically with either the High-Pressure Fuel Pump (HPFP) or the Low-Pressure Fuel Pump (LPFP). The N55 engine, while generally reliable, can experience these components failing over time.

  1. Check Fuel Pressure: This is the most direct way to diagnose fuel pump issues. A BMW specialist can connect a diagnostic tool to monitor both low-pressure (from the tank to the HPFP) and high-pressure (from the HPFP to the injectors) fuel readings during cranking and while the engine is running. Low pressure at either stage indicates a problem.
  2. Listen for LPFP: When you unlock the car or open the driver's door, you should hear a faint hum from the rear of the car as the LPFP primes the system. If you don't hear it, or it sounds weak, the LPFP might be failing.
  3. Inspect Fuel Filter: A clogged fuel filter (often integrated with the LPFP module in the tank) can restrict fuel flow and mimic fuel pump issues. While less common on newer BMWs, it's worth considering.
  4. Check for Leaks: Although less likely to cause long cranks, inspect fuel lines for any leaks that could be causing pressure loss.

Common OBD Codes:

  • P0087: Fuel Rail/System Pressure - Too Low
  • P008A: Low Pressure Fuel System Pressure - Too Low
  • Specific BMW codes (e.g., 29DC00 - Fuel pressure sensor, electric, short circuit to B+; 29F100 - Fuel pressure, plausibility)

When to See a Shop: Given the potential for stalling, it's important to address this promptly. Take your 2016 BMW M235i to a BMW specialist. They have the necessary diagnostic equipment to accurately read fuel pressure values, check for specific fault codes, and determine whether the HPFP, LPFP, or another component in the fuel system is at fault. Driving with a failing fuel pump can lead to poor performance, potential damage to other components, and unreliable operation.

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