S07.10-0057-79
Block diagram |
B4/6 | High-pressure fuel pressure sensor | Y76 | Fuel injectors | |
B37/4 | Accelerator pedal module | Y94 | Quantity control valve | |
B50 | Fuel temperature sensor | CAN C | Drive train CAN | |
B70 | Crankshaft Hall sensor | CAN E | Chassis CAN | |
M3/3 | Fuel pump with fill level sensor | CAN V | Vehicle CAN | |
N2/18 | Supplemental restraint system (SRS) control unit | A | Mercedes-Benz | |
N3/28 | CDI control unit | B | Nissan | |
N93 | Central gateway (CGW) | C | Default | |
N118 | Fuel system control unit (FSCU) | D | Optional |
Function requirements for fuel supply, general points
Circuit 15 (ignition ON)
Circuit 87 (Engine management ON)
Fuel supply, general points
The fuel supply supplies filtered fuel out of the fuel tank in adequate amounts under all operating conditions at an adequate pressure to the fuel injectors (Y76).
Function sequence for fuel supply
The function sequence for fuel supply is described in the following steps:
Function sequence for fuel pump actuation
Function sequence for fuel low-pressure circuit
Function sequence for fuel system high-pressure circuit
Function sequence for safety fuel shutoff
Function sequence for fuel pump actuation
To switch on the fuel pump with fill level sensor (M3/3), the CDI control unit (N3/28) sends the "fuel pump ON" signal to the fuel system control unit (FSCU) (N118). This signal is sent redundantly from the CDI control unit as a CAN signal via the drive train CAN (CAN C) and as a direct ground signal. Then, the fuel system control unit (FSCU) actuates the fuel pump with fill level sensor (M3/3) with a direct signal. The fuel system control unit (FSCU) also receives the CAN signal "Fuel specified pressure" from the CDI control unit.
Function sequence for fuel low-pressure circuit
The fuel low-pressure circuit consists of the following components:
Fuel tank
Fuel pump with fill level sensor
Fuel lines
Fuel filter
Quantity control valve (Y94)
Fuel system high pressure pump, low-pressure side
Fuel temperature sensor (B50)
The fuel system control unit (FSCU) evaluates the current fuel pressure, compares it with the specified pressure of the fuel and actuates the fuel pump with fill level sensor (M3/3) correspondingly so that the actual pressure corresponds to the specified pressure.
During actuation, the fuel pump with fill level sensor (M3/3) suctions the fuel out of the fuel delivery module and pumps it through the fuel filter to the fuel high-pressure pump. Depending on the fuel requirements, the fuel pressure is regulated to approx. 5.0 bar via the pressure limiting valve integrated into the fuel high-pressure pump.
The quantity control valve also regulates the supply of fuel to the fuel high-pressure pump (feed quantity) depending on the engine operating point in order to keep the fuel temperature low.
Any fuel not required flows back into the fuel tank through the return line.
Function sequence for fuel system high-pressure circuit
The fuel high-pressure circuit consists of the following assembly parts:
Fuel system high pressure pump
Rail
High-pressure lines
High pressure fuel pressure sensor (B4/6)
Fuel injectors
The fuel system high pressure pump pumps the fuel into the rail as a function of the signal from the accelerator pedal module (B37/4), the engine rpm and the fuel temperature.
From the rail, the fuel flows through the high-pressure lines to the fuel injectors. The fuel injectors spray fuel in a fine atomized form. The CDI control unit calculates the injection quantity selectively for each cylinder based on a characteristics map for the respective operating condition. The injection quantity depends on the fuel pressure in the rail and the actuation time of the fuel injectors.
The fuel pressure in the rail is controlled by the high pressure fuel pressure sensor. The effectively adjacent fuel pressure in the rail is recorded by the high pressure fuel pressure sensor. The fuel temperature is detected over the fuel temperature sensor. Both pieces of information are passed on permanently to the CDI control unit.
Function sequence for safety fuel shutoff
The safety fuel shutoff system is designed to ensure traffic and occupant safety.
The CDI control unit controls the safety fuel shutoff on the basis of the following signals:
Crankshaft Hall sensor (B70), engine speed
Supplemental restraint system control unit (SRS) (N2/18), direct crash signal
Supplemental Restraint System control unit (SRS), indirect crash signal via chassis CAN (CAN E)