Fuel Pump Module (FPM) (4.0L)
The electrically driven fuel pump module is located inside fuel tank. FPM delivers fuel to solenoid-operated fuel injectors, while fuel pressure is controlled by fuel pressure regulator.
Fuel Pump Module (FPM) (6.0L)
6.0L is equipped with 2 electrically driven fuel pump modules located inside fuel tank. The modules are identical but operate independently with staged control. One pump runs continuously when the engine is running. The other pump is activated when engine speed exceeds 2840 RPM. Each pump is activated by a separate relay.
Fuel pump relay No. 1 is switched by the fuel injection PCM. Fuel pump relay No. 2 is switched by the fuel pump control module. Fuel pump control module, located on right side of trunk, receives an engine speed input signal from the ignition PCM and switches fuel pump relay No. 2 ground as follows. When engine speed reaches 2840 RPM, the ground circuit is completed. As engine speed decreases, the ground circuit is interrupted at 2000 RPM. Switching of No. 2 fuel pump requires just 1/4 of a second, ensuring instant response for additional fuel delivery.
Fuel Pressure Regulator
Fuel pressure regulator is mounted on fuel rail. Actual (regulated) fuel pressure varies between 35-45 psi (2.5-3.2 kg/cm2 ) depending on intake manifold vacuum acting on fuel pressure regulator diaphragm. By maintaining constant fuel pressure, the quantity of fuel injected for a given duration of injector on time remains constant.
Inertia Fuel Shutoff Switch (IFSS)
On 4.0L, IFSS is located forward of driver-side fuse block. On 6.0L, IFSS is located on passenger's side footwell on front door pillar. On all models, switch is an inertia-actuated safety device which de-energizes ignition on relay, inhibits fuel pump module operation, and activates the central locking system to open all door locks should the vehicle be subjected to a heavy impact force.
Tuesday, April 20th, 2010 AT 4:45 AM