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Thread: Clicking behind driver seat -Resisitor fuel pump relay

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  1. Default Clicking behind driver seat -Resisitor fuel pump relay

    Hi,
    "I have a clicking sound like a relay opening and closing quickly behind the left seat. It sounds like some is tapping Morse code."
    "Just randomly stared one day and it happens at idle or while moving always when motor it operating temp not am Start when Engine cold. Have inspected the main relay which was fine no cracks and replaced both 4p relays on the bulkhead just to be safe. The car starts and drives fine but its an annoying sound. There are no codes and no other symptoms just clicking at various RPMs and drive states but nothing else correlates.
    I suspect that the relay or wires, connector is not the cause of the problem.
    That is definitely strange behavior. That relay should not be operating at low engine outputs. If you confirmed that you don't have some sort of intermittent ground on the red wire between the fuel pump relay and the ECU, then the ECU must be applying errant grounds causing the relay to operate (the ECU connects the red wire to ground to operate the relay). The ECU uses an internal transistor to switch the relay on and off; but when transistors fail they usually stay failed and most commonly as an open circuit. It might be possible that the ECU is getting some erroneous input signals causing the relay to engage and disengage.
    There were 3 cases described on Prime.
    I'm surprised by the solution:
    1. Replacing the alternator
    2. Repairing the engine-chassie ground (alternator replacing did not help)
    3.Replacing ignition switch (this case probably concerned the Main Relay)
    There is a verification procedure written in ETM. He suggests replacing my ECU with a functional one - confirmed from another car. I talked to R1 Motion, our friend from the forum. He has 37820-PBY-N01 Japan spec - mine is 37820-PBY-A01 US spec. It is not a cheap part (and there is no exact match) and the way the fault was solved on Prime means that I did not solve the problem. The common feature in solving the problem was power supply. (Alternator, ground). I noticed that these posts (errors) are from recent years. Our cars are getting old and knowing how to solve the problem can help others in the future. I encourage you to take action... I serve as an example.

  2. #2

    Default

    Have you actually confirmed that it is the fuel pump relay that is making the noise? If you drive the car and keep the RPM below 3000 RPM the fuel pump relay will stay open. This means that you should be able to carry out a test by driving the car with the relay removed. Do that and if the noise is no longer present then the problem likely originates from the fuel pump relay. Confirm that the noise returns by plugging the relay back in. If the noise does not go away when you unplug the relay then it is originating some place else.

    If it is the fuel pump relay I have no further comments on what might be causing the noise.

  3. Default

    I found another entry on Prime from 2017 that describes identical issue. This means that the symptom is the same clicking noise and occurs when the engine is warm. The next step I will take is to remove the alternator and send it to a specialist service.

  4. #4
    Join Date
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    Default

    have you isolated the unit making the clicking noise? if so, what happens if you unplug it?

    of the initial 3 options, the alternator overhaul is the most expensive!
    aka Jonathan!!

    '92 charlotte green auto.... as a daily
    '37 Ford Y street rod......... something for the weekend!

    ...... if a photobucket pic is foggy, click it, and it'll take you to the clear version, yes, it's a clicking faff....

  5. Default

    Asas I wrote in the first post. I'm sure about the part that makes the noise. This is fuel by pass resistor pump relay. If I unplug it, the noises disappear

  6. Default Corcuit diagram

    Fuel pump resistor by pass
    the relay coil is constantly powered by the plus and controlled by the minus via the ECU. More specifically, with a transistor inside the ECU
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by ozon02; 06-12-2023 at 08:27 PM.

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