OK Circuit for 5th injector, first the Fuel supply is on the main pressure line, The 2 wires on the 5th injector [ Black/yellow tracer...&...Brown/white tracer ] Black/yellow is 12volt + ONLY when you crank the engine this circuit is known as circuit 50..... the Brown/white is negative - only when the engine is Cold.. this negative comes from the "Thermo timer" Brown plug...once the engine warms up the negative is switched off via its "wax" element..there for not needed in Hot starting, as a safety feature circuit 50 is at Thermo timer so if the engine does not start theres a contact in Timer that heats up and break the negative as well..this is know as the "Bi-metal principle", resets itself after several mins of non-cranking, this prevents the intake manifold filing with fuel and possible explosion, this entire circuit is a separate loom..non-fused, so hope of help. Peter.