13B-8V4 MR-372-J84-13B000$020.mif
13B
DDCR INJECTION
Vdiag No.: 44, 48
System outline
The DDCR injection system used on the K9 engine is an electronically managed high pressure injection system.
The fuel is compressed by a high pressure pump then stored in a rail that feeds the injectors. Injection occurs when
a current pulse is applied to the injector holders. The injected flow is proportional to the rail pressure and to
the applied pulse length, and the start of injection is phased with the start of the pulse.
The circuit comprises two subsystems, which are distinguished by the fuel pressure level.
– The low pressure system includes the tank, diesel fuel filter, transfer pump and injector holder return pipes.
– The high pressure circuit contains the high pressure pump, the rail, the injector holders and the high pressure tubes.
Finally, there are a certain number of sensors and regulating actuators for controlling and monitoring the entire
system.
Functions provided
Function: Fuel supply management (timing, flow and pressure).
Quantity of fuel injected and injection timing adjustment
The injection checking parameters are the quantities to be injected and their respective timing. These are calculated
by the computer using signals from the following sensors:
• Engine speed (Crankshaft + Cam for synchronisation)
• Accelerator pedal
• Turbocharging pressure and air temperature (Turbocharger pressure)
• Coolant temperature
• Air temperature
• Air load (Flow and Pressure)
• Rail pressure
• Flowmeter
• Turbocharging solenoid valve
The quantities to be injected and their respective timing are converted into:
• a reference tooth
• the time between this tooth and the start of the pulse
• the time for which the supply to the injector holder is on
An electrical current (pulse) is sent to each injector holder according to previously calculated data. The system
makes one or two injections (1 pilot injection, 1 main injection). The general principle is to calculate an overall
injected flow which will then be divided into a main injection flow and a pilot injection flow, to help the combustion
process work properly and to reduce pollutant emissions.
An accelerometer is used to monitor some of the fuel injection deviation. This has several roles:
• Protecting the engine by detecting injection leaks (disabled on the basic vehicle).
• Checking the pilot quantity by measuring deviation and dispersion
• By changing both the duration and timing of the injection, the quantity of fuel injected and the mixture ignition timing
can be adjusted.
DIESEL INJECTION
Fault finding – System operation
13B-155V4 MR-372-J84-13B000$120.mif
DIESEL INJECTION
Fault finding – Tests13B
DDCR INJECTION
Vdiag No.: 44, 48
TEST 8 Injector return flow
NOTESSpecial note:
Certain faults make it impossible to carry out this test - deal with these first.
Does the engine start?
Command AC029 also checks the return volume of each injector to detect an internal injector leak.
Be careful with any objects (tool or other) on the engine housing during the four cycles of the operation
(possible vibrations).
Tooling required
–Mot. 1711 Injector flow measuring kit.
Or: Use four pipes with internal diameter 4mm and approximately 50 cm in length, and four graduated measuring
cylinders.
Procedure
– Ensure that the engine coolant temperature is above 60°C,
– switch off the ignition,
– disconnect the return pipes from the four injectors,
– cap the pump venturi tube to prevent the low-pressure circuit from depriming,
– connect the four transparent tubes in place of the return pipes,
– put the other ends of the four pipes into four graduated measuring cylinders.
– After finishing these preparations, start the engine and let it idle for 2 minutes.
Note: This idle time must be respected for the test results to be interpreted correctly.
–Run command AC029 High pressure circuit sealing check
.The engine will automatically carry out a cycle of four accelerations to increase the rail pressure and measure the
internal injector leaks under these conditions.
–Once the cycle is complete, run command AC029 again to obtain a correct reading of the return volume of
each injector.
– Switch off the engine at the end of the cycle.
NOA
YES
DDCR_V44_TEST08/DDCR_V48_TEST08
