Function: fuel supply Citroen Jumper II

Schematic diagram

Key

• "A" high pressure fuel circuit
• "B" fuel return circuit
• "C" low pressure fuel circuit
• "D" electrical links

Control of the injection

The engine ECU receives the requests from the driver, or from the vehicle (ABS, ESP, automatic gearbox, BSI), converting them into information on the necessary torque required of the engine

The engine ECU determines the quantity of fuel that is necessary to provide the engine torque that is required

Depending on the quantity of fuel calculated, the engine ECU determines the following parameters

• Fuel pressure in the fuel high pressure common injection rail
• Fuel injection time

To comply with the pollution norms, to limit the noise of combustion, and to improve the driving quality, the engine ECU determines the following parameters

• Fuel injection advance necessary (start of injection)
• Number of fuel injections per engine cycle
• Time of each injection of fuel during an engine cycle

Fuel pressure in the fuel high pressure common injection rail

When the engine speed and engine load are low, the engine does not require the maximum fuel injection pressure

The high pressure fuel sensor measures the pressure in the fuel high pressure common injection rail

The high pressure pump provides a maximum injection pressure of 1800 bars

To reduce the injection pressure, the engine ECU operates the following components

• Fuel flow regulation valve
• Fuel high pressure limiter

The excess fuel is then sent back to the fuel tank via the fuel return circuit

The injection pressure required is calculated as a function of the following parameters

• Intake air temperature
• Engine speed
• Engine load
• Coolant temperature
• Diesel fuel temperature

Injection time

Fuel injection pressure being equal, a longer (or shorter) injection time allows more (or less) fuel to be injected

When there is a large engine load need, fuel injection pressure being equal, the fuel injection time is extended to obtain the maximum engine torque

The fuel injection time is calculated as a function of the following parameters

• Intake air temperature
• Engine speed
• Engine load
• Coolant temperature
• Diesel fuel temperature
• Fuel pressure in the fuel high pressure common injection rail

Engine starting

On starting, the accelerator pedal position sensor signal is not taken into account

The injection flow and time are based solely on the temperature of the coolant using a special map

When the engine speed is sufficient, the accelerator pedal position sensor signal is again taken into account

Engine cold

A special map is used if the temperature of the coolant is insufficient (engine cold)

The engine management ECU makes the following corrections

• Increasing of the injection pressure
• Increasing of the injection time
• Increasing of the injection advance

Idling speed

The engine management ECU acts on the following parameters to maintain the engine speed at 800 rpm

• Injection pressure
• Injection time
• Point of injection (depending on the temperature of the coolant)

Compensation for fuel injector drift

The repeated injection cycles cause wear of the fuel injectors and a drift of the quantity of fuel injected

The drift in the quantity of fuel injected results in combustion noise and increased pollution

The following parameters allow the engine ECU to calculate the drift in the quantity of fuel injected

• Engine torque
• Engine mixture measured by the proportional lambda sensor

The engine management ECU checks the regularity of the engine torque and adjusts the injection time for each cylinder

The engine management ECU calculates the nominal engine mixture and compares it with the signals from the oxygen sensor and the mass air flow sensor

The engine ECU compensates for the drift in the quantity of fuel injected by applying a correction to the injection time

Fuel injection

Point of injection

"E" top dead centre

"F" crankshaft angle

"f" fuel pilot injections

"g" fuel main injections

"h" fuel post-injections

The fuel injected into the combustion chamber requires time to ignite

The engine ECU injects the fuel before top dead centre to compensate for the delay in the fuel igniting

There is one moment of injection for each injection of fuel in an engine cycle

• The fuel pre-injections are positioned in the range "f"
• The main fuel injections are positioned in the range "g"
• The fuel post-injections are positioned in the range "h"

The engine ECU determines the moment of injection as a function of the following parameters

• Information from the camshaft sensor
• Information from the engine speed sensor
• Engine load
• Air temperature
• Engine coolant temperature
• Vehicle speed
• Atmospheric pressure

In the engine starting phase: the engine ECU increases the injection advance so as to facilitate engine starting and reduce pollutant emissions

During the particle emission filter regeneration phase

• The engine ECU retards the injection (post-injections)
• The combustion terminates in the catalytic converter, which increases the temperature of the exhaust gases

Number of fuel injections per engine cycle

"E" top dead centre

"F" crankshaft angle

"j" first pre-injection

"k" second pre-injection

"l" first main injection

"m" second main injection ("split" injection)

"n" first post-injection

"p" second post-injection

"q" third post-injection

Pilot injections

Pre-injections inject a small quantity of fuel prior to the main injection, in order to increase the temperature in the combustion chamber

The increase in temperature in the combustion chamber permits faster and less sudden igniting of the diesel than during a main injection without pilot injection

The pilot injection reduces the noise linked with the fuel combustion

The pilot injection is deactivated when the engine speed is higher than 2200 rpm

Main injection

The majority of the fuel quantity is injected in the main injection; the combustion produced by the diesel fuel igniting generates the movement of the piston (creation of torque)

The main injection can be separated, giving rise to a second main injection called "Split injection"

The "split" injection causes an increase in the temperature of the exhaust gas, which brings the catalytic converter up to temperature and reduces emissions of nitrogen dioxide (NOx)

Post-injection

Post-injection is used during regeneration of the particle filter and consists of injecting a quantity of fuel after the top dead centre of the piston in the exhaust phase

The excess fuel is burnt up inside the exhaust manifold close to the catalytic converter and the particle filter

The number of post-injections during regeneration of the particle filter is dependent on engine load and on the temperature of the particle filter

• 1 post-injection under heavy engine load
• 2 post-injections under medium engine load
• 3 post-injections under light engine load

The increase in the temperature of the exhaust gases enables the destruction of the particulates that are retained in the particle filter

Injection flow reduction strategies

The engine management ECU can apply several injection flow limitation strategies in the event of a fault in a component of the injection system

The flow limitation strategies authorise the engine to operate but with a limited engine speed and torque, the severity of the limitation depending on the fault

The injection flow limitation strategies are applied in the event of a fault in a component of the injection system

If the temperature of the diesel exceeds 75°C, the engine management ECU reduces the injection flow and pressure (the injection time does not vary)

If the temperature of the diesel reaches 90°C, the engine torque is reduced by 40%

The engine ECU acts on the fuel flow regulation valve and on the injectors to reduce the flow of fuel injected

When the injection flow limitation strategies are applied, the following functions are deactivated

• Exhaust gas recycling (EGR)
• Assistance with the regeneration of the particle filter

Diesel fuel injection stop (in the event of a collision)

An inertia switch permits stopping of the supply to the fuel circuit in the event of an impact, earthing the electric scavenge pump located at the fuel tank

The inertia switch is located under the fascia panel, on the passenger side

The engine management ECU cuts off the injection when it receives the booster pump earthing information

The inertia switch is connected by wire to the built-in systems interface

The built-in systems interface carries out the following actions if an impact is detected by the inertia switch

• Unlocking of the doors
• Switching on of the interior lights

The inertia switch is reset by pressing the push button located on its upper section