Sorry for any confusion. The wiring shown in the Jake installation manual is for a truck that was not built with the Jake harness integrated. I don't happen to have a wiring diagram for your year model handy, I do have one for a CH 1993-1994 with factory wiring for Jakes which should be set up about the same as on the RD with the biggest difference being wire numbers (which you probably can't read anyway due to fading). They may or may not be the same, I'm not sure. I have removed the extra wiring shown on the diagram so all you see is the engine brake wiring. The wire numbered 22-A-.8 is the first wire in teh circuit, it goes from the fuse to the jake switch and the relays. When the jake switch is turned on low power goes to pin 85 on the low relay, it goes to pin 85 on both relays in high position. Power goes through the relay and exits on pin 86 and goes to the clutch switch, form the clutch switch to the fuel pump switch, from the pump switch to ground. when this happens the relays (either the low if in low position or both if in high position) switch internally from pin 87a to pin 87 allowing power to flow from pin 30 through the relay and out to the jake solenoids. Some or all of this circuit may still be intact on your truck, you might want to check the jake housings on the left side to see if there are any wires connected to them and so on. Factory Jake Wiring.pdf