Hi I have a 91 civic and I have replaced the main relay the dristrubitor and all its componits including the plug wires and plugs and I got another ecu out of the salvage yard and my ? Is why would the main relay buzz when the ignition is on or when trying to start the car any advise on the situation would be apriciated thanks.:confused:

It will buzz if the ECM is bad. The ECM controls main relay terminal 8, which is a computer controlled grounding terminal. Run the K-Test on your ECM, which is described in Section A below:

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