Question about 2001 Mercedes-Benz C-Class

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No power to fuel pump on 2002 C240 model

There is no power to the fuel pump when turns the key in start position.  What causes the problem?

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  • ntliem May 23, 2009

    Thank you very much for your advice. I will check that and let you know the progress. I have to look for the electrical diagram in able to do that check first in the morning.

  • ntliem May 23, 2009

    Thank you. I fixed the problem. It was the relay.

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Hello and thanks for choosing FixYa.com!

Try inspecting your vehicle's fuel pump relay. The relay is a sort of "OFF/ON" switch that sends signals to the fuel pump when the ignition switch is turned. If it has failed, the fuel pump will not get a signal to power on.

Posted on May 23, 2009

  • Joseph Dugger
    Joseph Dugger May 23, 2009

    Hello and thanks for choosing FixYa.com!



    Try inspecting your vehicle's fuel pump relay. The relay is a sort of "OFF/ON" switch that sends signals to the fuel pump when the ignition switch is turned. If it has failed, the fuel pump will not get a signal to power on.

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Its the crank positioning sensor

Posted on Jun 10, 2009

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At those times when it doesn't want to start, you should test the fuel pressure to see if the fuel rail is pressurized. If no pressure or low pressure, diagnose the wiring at the fuel pump relay. The relay is very simple- 4 prongs, 2 on the power side, and 2 on the coil side. The power side has a hot at all times wire and then the wire going to the pump. The coil side of the relay has a wire from the engine computer, and the other coil side wire is a ground. When the coil side is energtized by the wire from the computer, the relay is switched on and will pass power from the hot wire to the pump. So if the pump doesn't come on briefly to prime the system, the computer may not be signalling the relay, or there is a wiring problem around the relay. Good luck. You might just try a different relay-maybe yours is sticky and not responding.

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ok so ntheres power at the relay is the relay bad get a piece of pretty heavy wire not small speaker wire a little bigger than that about 6 inches or so strip off both ends pull out fuel relay turn key on position stick wire down into slots where relay plugged in one of these is a ground so it will spark so u know not to stick it back in that one but check alln rest until you hear the fuel pump kick on or get under car at gas tank unplug fuel pumphave somebody turn key on and off and u test it with test light ton make sure you are getting power to pump if you are then pump is bad

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Do you mean it cranks but won't start?
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Observe that the vehicle fails to start and that the security light is illuminated. leave the key in the 'ON/Accessory' Position. (DO NOT turn key to the 'off' position.)
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