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(With thanks to "Tezza".) If you want the cranking prime function (during starting), you may have to connect a diode in series with 87 to prevent any feedback to the starter solenoid. Otherwise a plain SPST relay will suffice. For priming (aka bypass), you can then diode-OR the Charge-Lamp & starter circuit or a separate momentary push button.) If the alternator/regulator fails, by disconnecting the alternator's regulator, the dash lamps (ie, the charge lamp and any diode-interconnected lamps) are usually sufficient to power the relay. (IE - being disconnected, the regulator's earthed "charge lamp" terminal will not hold the relay #86 low.) This circuit assumes that the fuel pump is NOT used as an engine protection device or "kill switch" (that's what the oil pressure to ignition circuit is for) but is merely required to turn off should the engine stall or ignition be turned off. It also overcomes the oil-pressure reliability issues (eg - stuck pressure switch; open contacts/wires). Many cars use this approach for fuel pump control. It is simple and reliable and merely adds a relay to existing circuitry. Newer cars may use air-flow switches if fitted, but these are usually on EFI vehicles whose EMS control the fuel pump anyhow.