Black and sooty spark plugs means you are not burning the gas…………
The reason can be weak spark, bad plugs, too much gas, timing, low compression, plug wires, ?
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On Sep 22, 2024, at 10:02 AM, Herman via groups.io <h3ch4@...> wrote:
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Sounds like a fuel pump issue. Sometimes when they fail, the flow rate slowly drops as they warm up. By disconnecting the FPR vacuum line, you are raising the fuel pressure at idle (spec is 36psi with vac connected, 43psi disconnected) to compensate for the reduced flow rate.
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There's a procedure in the service manual to check the fuel pump flow rate (~500ml over 30s at 43psi) but a simpler test that you do is to hook up a fuel pressure gauge and see if the pressure starts to fall below 36psi at idle.
