Re: Fuel shutoff sol 1994 U280 Cummins 8.3
Reply #4 –
Expanding on Peter's (oldguy) comments, the 3 wires going to the fuel shutoff solenoid are:
WHITE (pull-in or suck-in winding)
RED (hold-in winding)
BLACK (ground)
The WHITE wire is a high amp draw circuit (20-30 amps, momentary duty, only when starter motor is engaged)
The RED wire is a low amp draw circuit (about 1 amp, continuous duty, as long as ignition switch is ON)
Studying the B-2037 U280 12V Wiring Diagram, we can deduce that the hold-in circuit (RED wire) is powered directly off the small "activation" post on the IGN SOL (located under the lift-up dash cover on U280). This "activation" post is HOT as long as the ignition switch is in the ON position. The fuel shutoff solenoid BLACK ground wire is also shown on this diagram.
As you have observed, the B-2037 Wiring Diagram does not indicate the power source for the WHITE wire - or at least I connot find it. The diagram linked below (Cummins Marine Fuel Shutoff Solenoid Wiring) shows the WHITE wire being powered off the "downstream" (non-battery) side of the F496 relay. The F496 relay corresponds to the AUX START SOL on the U280 C8.3 (see the B-2126 U280 Automotive Wiring Diagram). This power source makes perfect sense because the "S" post on the AUX START SOL is only hot when the ignition switch is in the START position.
I believe the "S" post on the AUX START SOL is the most logical source for power to the WHITE wire on the fuel shutoff solenoid. I have no idea why this circuit is not shown on the FOT wiring diagrams.
NOTE: Since I have never actually traced the fuel shutoff solenoid power supply wires on my coach, everything I have stated above is OPINION based on my interpretation of the diagrams. TIFWIW.
Fuel Shutoff Solenoid Wiring 101 - Seaboard Marine
Topic: Fuel shutoff sol 1994 U280 Cummins 8.3