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Mercedes-Benz of Stevens Creek

Mercedes-Benz C 240 Fuel Pump Problems - How To Troubleshoot and Fix

Your Mercedes-Benz C240's fuel pump is an integral part of your vehicle's operation, delivering fuel from your fuel tank to your engine. It helps regulate fuel pressure, dispersing the correct amount of fuel based on driving conditions. Climb uphill or pump the gas hard and your fuel pump goes into overdrive to compensate.

Keep reading to learn more about these signs, your Mercedes-Benz C240 fuel pump location, how to check Mercedes-Benz fuel pump relay, and how to repair your Mercedes-Benz fuel pump.

Mercedes-Benz C 240 Fuel Pump Location

Your Mercedes-Benz C 240's fuel pump is located in your gas tank beside a regulator that helps moderate your fuel pump's output.

Common Symptoms of A Bad Fuel Pump

Strange Noises Coming from Your Fuel Tank

Your fuel tank area may make odd whirring or grinding noises, especially when driving at higher speeds. This may be the result of irregular fuel pressure going to your engine, delivering too little fuel for your vehicle's demands.

Loss of Power

A bad fuel pump results in loss of power, especially when carrying heavy cargo or accelerating uphill. Remember, during more strenuous driving conditions, fuel pumps become overworked. An overage of fuel may also result due to poor fuel regulation by your fuel pump, resulting in a stalled or erratic engine.

On a separate note, a lack of fuel pump pressure could also cause your engine to overheat. Any incorrect amount of fuel from your fuel pump to your engine could cause it to stall or lose power.

Check Engine Light Comes On

A check engine light may be a sign your fuel pump is overheating, resulting in a drop in fuel pressure.

Test For A Defective Fuel Pump

Troubleshooting, diagnosing, and repairing a defective fuel pump is a relatively straightforward process that requires locating your fuel test port and using a fuel pressure gauge to check if enough pressure is being fed from your fuel tank to your engine.

Here are the steps needed to check for a defective fuel pump on your Mercedes-Benz C 240. You will need a fuel pressure tester, which can be purchased from the Mercedes-Benz national store.

  1. Open your Mercedes-Benz C 240's hood, locate, and remove the engine cover.
  2. Accessing your fuel rail's fuel pressure port, lift off the Schrader valve cap, and connect your fuel pressure tester.
  3. Turn the vehicle on; do not start the engine.
  4. Record the pressure reading.
  5. Confirm your fuel pressure tester shows a range of 47 – 55 PSI on idle. A 54 – 61 PSI is an acceptable range if your vacuum hose is disconnected.
  6. Start your engine and record the pressure reading again.

If you are uncomfortable completing any of these steps, we highly recommend visiting a licensed Mercedes-Benz technician/dealership for assistance. 

Keep in mind, checking a fuel pump is normally not part of a routine maintenance program, meaning it is not checked at periodic intervals. Fuel pumps can become defective at mile 100 or mile 100,000. As a best practice, fill up your fuel tank with every gas station visit and check for clogged fuel filters.

Replace A Defective Fuel Pump On Your Mercedes-Benz C 240

Before starting, have a ratchet wrench set (universal joint), open-end wrenches, screwdriver, and a bolt handy to plug into your fuel line.

  1. Disconnect your fuel pump's fuel tank hose and plug it with a wooden dowel or bolt to prevent fuel from leaking.
  2. Disconnect all fuel hoses, emissions hoses, and connections.
  3. Remove your pump assembly's retainer ring and remove the fuel pump before aligning your new replacement fuel pump in place.
  4. Reconnect all fuel hoses, emissions hoses, and connections.
  5. Perform a test drive to note for any potential issues with the re-installation.

All in all, your fuel pump is integral to your Mercedes-Benz C 240's operation. Without a working fuel pump, your fuel tank cannot effectively feed and optimize the amount of fuel delivered to your engine, causing stalling and erratic driving conditions.

Check for all of the symptoms and troubleshooting steps outlined above to fix your fuel pump issues. Get an OEM Mercedes-Benz Fuel Pump here.