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2017 Colorado Hard Start/Stalling - Fuel System?

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Sarah K. · rep 0 · May 22, 2:39 AM · 1 replies · solved · Question

Vehicle: 2017 Chevrolet Colorado Z71

Hey everyone,

I'm having some intermittent but concerning issues with my 2017 Chevrolet Colorado Z71, 3.6L V6. Sometimes, it cranks for a long time before finally starting, and a couple of times it has stalled shortly after starting, especially on colder mornings. It feels like it's not getting enough fuel.

I've also had the check engine light come on a few times, and I pulled codes P0300 (Random/Multiple Cylinder Misfire Detected) and P0440 (Evaporative Emission Control System Malfunction). Could these be related to a fuel pump or another fuel system component?

I'm looking for advice on where to start troubleshooting this. I want to avoid just throwing parts at it. Any common issues with the fuel system on these Colorados?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 2:39 AM

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ClearTheCode admin answer:

Your 2017 Chevrolet Colorado's hard starting, stalling, and the combination of P0300 and P0440 codes strongly suggest an issue within the fuel and/or evaporative emission (EVAP) system. These systems are closely linked, and a problem in one can affect the other.

Potential Causes:

  1. Fuel Pump/Fuel Pressure: A failing fuel pump or a weak fuel pressure regulator can lead to insufficient fuel delivery, causing hard starts and misfires. The pump might not be building enough pressure quickly enough, or it could be losing pressure when the engine is off (check valve issue).
  2. Fuel Pump Relay: A faulty fuel pump relay can intermittently prevent the pump from receiving power, leading to starting issues.
  3. EVAP System Leaks/Faults: The P0440 code points directly to a general malfunction in the EVAP system. This system prevents fuel vapors from escaping into the atmosphere. Common culprits include:
    • Loose or faulty gas cap: Always check this first.
    • Purge valve or vent valve: These valves can stick open or closed, causing pressure issues in the fuel tank.
    • Leaking EVAP lines or canister: Cracks or damage can create a vacuum leak.
  4. Ignition System (P0300): While P0300 can be caused by fuel issues, it's also worth considering spark plugs or ignition coils, especially if the fuel system checks out.

What to do:

  1. Check Gas Cap: Ensure your gas cap is tightened properly. If it's old or damaged, replace it.
  2. Fuel Pressure Test: A mechanic can perform a fuel pressure test to determine if the fuel pump is delivering adequate pressure to the engine, both at rest and while running.
  3. EVAP System Smoke Test: For the P0440 code, a smoke test of the EVAP system can help pinpoint leaks in hoses, the canister, or faulty valves (purge or vent solenoid).
  4. Inspect Fuel Pump Relay: The relay can be tested or swapped with a known good one (e.g., horn relay, if compatible) for a quick diagnostic.
  5. Scan for Pending Codes: Use an OBD-II scanner to check for any pending misfire codes (P0301, P0302, etc.) that might indicate a specific cylinder, which could point to a bad spark plug or coil.

When to see a shop:

Given the combination of hard starting, stalling, and both P0300 and P0440 codes, it's best to have a qualified mechanic or Chevrolet dealership diagnose the issue. They have specialized tools for fuel pressure testing and EVAP system diagnostics (like smoke machines) that are crucial for accurately identifying the root cause without guessing. Addressing EVAP issues is important not only for performance but also for emissions compliance.

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