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Q: Vehicle will sometimes turn over, but not start

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Sometimes my vehicle will turn over, but it won’t start. The crank sensor was replaced and a local import repair shop reported that they think it to be the main computer because the fuel pump is getting too much. Randomly the vehicle will start over and over, but other times it only turns and won’t start. Can you tell me what could be causing this?

Based on your description, it sounds like your 2007 Mercedes GL450’s fuel pump may be randomly shutting off. This can be due to a malfunctioning powertrain control module as the repair shop told you. This can also be related to a faulty fuel pump, loose wire, faulty fuel pump relay, faulty ignition switch, or a clogged fuel filter.

I would recommend having your fuel pump’s electrical circuit inspected for damages and tested with a digital multimeter in various locations to determine if the circuit is performing its intended purpose. If any damaged wires are located, they should be replaced immediately as this can cause the symptoms you are having. It is also very important to check near the power distribution center under your hood for the fuel pump relay and see if any damages are found there as well. A certified technician from YourMechanic can diagnose your starting issue if you need further help.

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