Fuel Pump: Description and Operation

Fig. 1 Electric fuel pump & sender assembly. 1984 - 87 Ford:

Fig. 3 Fuel pump wiring diagram. 1985 - 87 V8-460 models w/single fuel tanks:

Fig. 5 Fuel pump wiring diagram. 1985 - 87 V8-460 models w/dual fuel tanks:

1985 - 87 V8-460 ENGINE & HOT FUEL HANDLING SYSTEM


The in-tank low pressure fuel pump, Fig. 1. used on 1985 - 87 models, is capable of supplying approximately 25 gallons of fuel per hour at 4.3 psi. The fuel pressure is controlled by a vapor separator on the engine working together with the carburetor float valve. The vapor separator has an internal orifice which returns fuel to the fuel tank through a return line. This separator limits the maximum system pressure and helps keep the fuel cool.
On vehicles with single fuel tanks, the electrical system, Fig. 3, provides power to the pump through two relays: starter relay and fuel pump cut-off relay. On vehicles with dual fuel tanks, the electrical system, Fig. 5, provides power to the pump through three relays: starter relay, fuel pump cut-off relay and fuel tank selector relays. On all vehicles, the current path is dependent on operating conditions.
In the event of a collision, the inertia switch contacts open and the fuel pump automatically shuts off, even if engine operation continues. The engine will stop a few seconds after fuel pump operation stops and cannot be restarted until the inertia switch is manually reset. The inertia switch is located behind the instrument panel on 1985 models, on the toe board to the right of the transmission hump on 1986 - 87 F Series models or on the passenger side cowl panel just forward of the right front door on 1986 - 87 E Series models.