Description of Fuel Supply Electrical System

FIGURE 13:

FIGURE 14:

FIGURE 15:

The fuel system electrical circuits are shown in schematic form in Figures 13, 14 and 15.

How the Circuit Works - Electric Fuel Pump Control (Single Tank) (Figure 13)
With the Ignition Switch in RUN and the Oil Pressure Switch closed (engine running), the Fuel Pump Cutoff Relay coil is energized. The contacts in the relay close and the pump in the Fuel Tank Unit is powered by Fuse Link Q. The voltage at the pump is reduced slightly by the voltage drop across the 0.75 ohm Resistance Wire. The Inertia Switch will open on impact and cut off current to the Fuel Pump Cutoff Relay in the event of a collision.

With the Ignition Switch in START current flows from Fuse Link R to the pump bypassing the Fuel Pump Cutoff Relay and the 0.75 ohm Resistance Wire. This provides extra fuel pressure during start.

FIGURE 14:

FIGURE 15:

How the Circuit Works - Electric Fuel Pump Control (Dual Tanks) (Figures 14 and 15)

The Electric Fuel Pump Control (Dual Tanks) circuit allows fuel to be drawn from either the Front or Rear Fuel Tank Units.
With the Ignition Switch in RUN and the Oil Pressure Switch closed (engine running), the Fuel Pump Cutoff Relay coil is energized. The contacts in the relay close, and current flows from Fuse Link Q to the Tank Selector Relay. Depending on which position the Fuel Selector Switch is in (Front or Rear), current then flows to either the Front or Rear Fuel Tank Unit to power the pump. The voltage at the pump is reduced slightly by the voltage drop across the 0.75 ohm Resistance Wire. The Inertia Switch will open on impact and cut off current to the Fuel Pump Cutoff Relay in the event of a collision.

With the Ignition Switch in START current flows from Fuel Link R to the Tank Selector Relay bypassing the Fuel Pump Cutoff Relay and the 0.75 ohm Resistance Wire. Depending on which position the Fuel Selector Switch is in (Front or Rear), current then flows to either the Front or Rear Fuel Tank Unit to power the pump. Bypassing the Fuel Pump Cutoff Relay and the 0.75 ohm Resistance Wire provides extra fuel pressure during start.
The Fuel Tank Selector Switch controls which Fuel Tank Unit is used. When turned to the FRONT position, current flows from Fuse 4, through the FRONT contacts of the Fuel Tank Selector Switch, and to the motor in the Tank Selector Valve. The motor operates and the switch contacts and fuel valve transfer to FRONT position. The sender in the Front Fuel Tank Unit is connected to the Fuel Gage. The coil in the Tank Selector Relay is energized and the contacts move to the FRONT position, allowing current from Fuse Link Q to flow to the Front Fuel Tank Unit. This allows the pump in the Front Fuel Tank Unit to operate.

When the Fuel Tank Selector Switch is turned back to REAR, current flow is reversed through the Tank Selector Valve. The motor operates and transfers the switch contacts and the fuel valve to REAR position. The sender in the Rear Fuel Tank Unit is connected to the Fuel Gage. The coil in the Tank Selector Relay is non-energized and spring tension moves the contacts to the REAR position allowing current from Fuse Link Q to flow to the Rear Tank Unit to operate the pump.