This part of site is an attempt to organize and add to the web resources for the Rover SD1
to form a cohesive and easily usable guide for those of us without easy access to
expert repair and/or advice. It is not offered in any way as a definitive source
and we take no responsibility for any errors that may exist.
the webmaster Rene Winters.
Lucas EFi |
Legislation in many countries requires a reduction in level of noxious exhaust gasses.
For many years this has been achieved by using an oxidising catalyst to remove any unburnt
hydrocarbons and carbon monoxide and exhaust gas recirculation, EGR to reduce the
formation of nitrogen oxides.
However stricter legislation for the 80's is demanding even lower levels of these harmful
To satisfy the requirements, a new type of catalyst, the three way catalyst, has been
developed. It not only removes hydrocarbons and carbon monoxide, but simultaneously
breaks down nitrogen oxides to nitrogen and oxygen two harmless gasses, but for the process
to work efficiently, the engine must be supplied with a stoichiometric, or chemically
correct, air/fuel mixture, under all driving conditions.
That is, in the proportion of fourteen volumes of air to each volume of atomised fuel.
Such precise control is not possible with conventional carburettor systems and has led to
the introduction of fuel injection on many of our cars.
On this page "The Lucas EFi", we are going to introduce you to the new digital L-Jetronic
system, incorporating "closed loop'' mixture control.
This is now standard equipment on Rover SD1 and Triumph TR8 vehicles destined for certain
markets. Although we will be looking at a North American Rover SD1 V8.
L-JETRONIC FEATURES |
L-Jetronic does however have more to offer than just a clean exhaust. More accurate
fuelling means improved engine performance and economy. It even accounts for engine
cylinder manufacturing tolerances and wear during service.
The function of "closed loop" mixture control is to maintain the stoichiometric air/fuel
mixture under all driving conditions.
The injection system comprises a fuel supply circuit an electronic control unit, or ECU
and several devices that continuously monitor engine condition. Information from these
devices is processed by the ECU and used to determine the fuel supply to the engine.
The main determinants are engine air intake, engine speed and exhaust oxygen level.
Provision is also made for cold-start and warm-up enrichment.
FUEL SUPPLY |
Lets have a closer look at the system. We will start with the fuel supply. The pump is
located under the floor and is driven by an electric motor.
The pump has a rotor fitted with several metal rollers positioned in notches around its
circumference. When the motor is running the rollers form sealed cells which force fuel
through the pump housing.
In the event of excessive pressure build up, a safety valve short circuits the suction and
discharge sides of the rotor. A non return valve in the outlet union prevents a pressure
leak from the fuel lines after the pump stops running and aids restarting the engine.
From the pump, high pressure fuel is filtered. then passed to a fuel rail, which supplies
the injectors, one for each engine cylinder.
The rail encircles the plenum chamber. a special air collection chamber, between the
throttle plate and the inlet manifold branches.
Pressure in the rail is determined by this regulator. Excess fuel is returned to the tank.
The regulator is divided into two chambers by a spring loaded diaphragm. Fuel pressure in
the lower chamber depresses the diaphragm against the spring, thus allowing fuel to return
to the tank.
To ensure that the amount of fuel injected depends only on the opening time of the
injectors, the spring chamber is connected, by a hose to the inlet manifold.
As the vacuum signal varies, so does the load on the diaphragm. This arrangement causes
fuel pressure to vary with manifold depression.
The injectors are located in the inlet manifold branches, just ahead of each inlet valve.
They have a solenoid operated valve, and a specially designed nozzle to ensure complete
The solenoids are energised via a power resistor pack. It has a separate resistor for each
injector. Its purpose is to prevent damage to the ECU in the event of a short circuit.
On the V8 engine the injectors operate in banks of four, the two banks operating
alternately, twice each engine cycle.
A cold-start injector is also connected to the fuel rail. It sprays finely atomised fuel
into the plenum chamber during cranking.
Its operation is controlled by a thermal time switch, located in the coolant, where it can
sense engine temperature.
To end this first section of the programme, study this diagram of the fuel system.
You should now be able to identify each component.