Fuel Delivery and Air Induction: Description and Operation

PURPOSE
The multi-point fuel injection systems (Digital Motor Electronic (DME) 1 - cylinders 1-6, and DME 2 - cylinders 7-12), delivers a precise quantity of fuel to each cylinder under all engine speed and load conditions.

COMPONENTS
^ Fuel tank (cell)
^ Electric fuel pumps
^ Fuel delivery and return lines
^ Fuel filters
^ Pressure regulators
^ Electric injection valves
^ Air filters
^ Induction systems
^ DME control modules

OPERATION
The electric roller-cell pumps supply high volume fuel from the tank to each fuel injector. Large volume injector rails ensures equal distribution to each valve. The injector rails are fitted with a pressure regulators which maintain a constant pressure differential (fuel pressure and manifold pressure) at the injection nozzles. Excess fuel is directed back to the fuel tank. Because of the constant flow, cool fuel prevents formation of vapor bubbles and ensures good hot starting.

Since fuel pressure is held constant, fuel injection quantity is dependent upon the frequency and duration of the injection pulses. DME constantly calculates the amount of fuel needed and adjusts injector signals via output stages within the ECU`s.

V12 Component Location:

V12 Engine Front View:

NOTE: To achieve good mid-range torque characteristics, long air intake pipes are used. This method of induction requires that the plenum chamber for the left bank (cylinders 7-12) be mounted on the right side of the engine, and the plenum for the right bank (cylinders 1-6) be mounted on the left side of the engine. The technician must keep this in mind when referring to component locations and testing procedures. Components such as air intake sensors, air mass sensors, injectors, throttle position motors and induction systems may be misdiagnosed because of the possible confusion. Remember that fault codes will always refer to the DME system (DME system 1 = CYL. 1-6) and (DME system 2 = CYL. 7-12).