Rover's Vikingship Fuel Injection Rover's Vikingship

The EFi (Electronic Fuel injection) system for the Rover SD1 is actually the well known Bosch L-jetronic system adapted by Lucas. Most components are manufactured by Boschje itself (As you can see by the "made in Germany" labels.......already a sign for the German BMW connection?).

Fuel injection first appeared in Diesel engines back in 1927. Off course this was a Bosch system. This German company can be seen as the main force behind all modern EFI systems. The first 4-stroke production car equipped with fuel injection was the 1952 Mercedes Benz 300 SL which had direct injection into the cylinders. Later on more advanced systems were developed by Bosch. Shown below is a short overview.

Mercedes Benz 300SL  (21,0 kB)

SystemPrincipleBuilt into
Mechanical injection Direct injection, Mechanical Mercedes 300 SL
D-jetronic (1967)
D=Druck (Pressure)
Electronic system, fuel quantity based on manifold pressure BMW 3.0Si (early types)
Citroen DS/SM
Jaguar XJS/ XJ12
Mercedes 250E
VW type 3/4
K-jetronic (1973)
K=Kontinu (Continuous)
Electronic system based on air flow, continuous fuel injection Mercedes 300SEL
Saab 99
Volvo 142, 144, 145
L-jetronic (1973)
L=Luft (Air)
Electronic system based on air flow, intermittent fuel injection Alfa Romeo GTV 2.5/Spider
BMW 628/630 Csi
Jaguar XJ6
Lancia HPE
Opel Senator/Monza

Thriumph TR5 PI  (16,9 kB)

Lucas had its own Fuel injection system, based on Bosch, built into a Jaguar D-type back in 1957. Later the Maseratis 3500GT, Sebring 109, 5000GT and 107 were also equipped with the Lucas system. The real break through for Lucas came with the mechanical fuel injection system built into the Thriumph 2.5PI range and the TR5/6.

The Triumph injection was developed by Lucas after the first wave of U.S. anti-emissions regulations. However it soon became clear the injection system would need extra environmental controls and that a carefully set Zenith-Stromberg carburetor could also do the job. For extra power though the Lucas injection proved to be very good. So this is how Europe got the Injection first and the U.S. had to do with carburetors for that time! You can find the schematic for the mechanical Lucas system below.

Mechanical injection (Lucas)  (6,5 kB)

For the SD1's on the U.S. and Australian market an injection system based on Bosch L-jetronic components was used. Thanks to the emission regulations power for the SD1 was down to 133 bhp respectively 150 bhp for the Australian EFi, against 155 bhp for its European counterparts equipped with two SU HIF 6 carburettors. The 22 bhp went into the catalytic converters (not fitted on the Australian SD1's), the Oxygen sensor and a rather restrictive plenum chamber. The U.S. cars could still reach 117 mph though, opposed to 126 mph for the Euro versions

When Rover became involved in motorsports in the early 80's the management and the Competition department soon found eachother in creating a powerful SD1 for the upper market. The Australian injection system was used as a basis with a better plenum chamber, a revised air-flow meter, ECU, and a different distributor characteristic. Coupled with the additional compression increase to 9.75:1 the power of the Vitesse as the car was called, went up to a healthy 190 bhp. This EFi system was used in the same form in the Vandenplas EFi and in a somewhat detuned form in the Range Rover line-up.

These pages will introduce you into the basics of the Bosch/Lucas L-jetronics system. Whether for an SD1 or a Range Rover.

Lucas/Bosch L-Jetronic...the basics

Click on the map for a description of the selected part

Fuel is drawn from the tank to a high pressure pump which pushes the liquid gold through a fine mazed filter to the fuel pressure regulator. The excess fuel is drained back into the tank. The fuel is then transported through a fuel rail to the injectors and the cold start injector. The air is drawn in from the air filter through the air flow sensor which incoporates a temperature sensor. From there the air flows through the plenum chamber into the engine. The injectors are opened for a short time.

The duration is calculated by the ECU and depends on:

  • Air flow measured by the air flow sensor
  • Air temperature
  • Engine temperature
  • Position of throttle butterfly

The tank can be as standard as on a carburetted car. However it is even more important to avoid tankvacuum because the fuel pump has greater suction power which can suck the tank inwards! In the Range Rovers the fuel pump is built into the tank. On the SD1 the fuelpump is located under the car.


The fuel pump is operated by an electric motor which is cooled by the fuel itself. Don't worry of the pump bursting into flames as the pump never contains an ignitable mixture. The pump has two stages. A low pressure vane typepump which is able to suck in the fuel even after the tank was totally empty. And a high pressure roller type pump which is not capable of transporting air and therefore is relying on the vane pump to prime it after a totally empty tank . To prevent too high fuel pressures there is a relief valve incorporated which also guarantees fuel flow when there is little need for fuel from the engine. (The pump needs to be cooled even when the engine is idling).


Fuelpump 2,4 kB

The filter is a 2 micron filter to prevent all kinds of foreign particles damaging the injectors or the internals of the engine. It should be replaced every 40,000 miles. On the SD1 it is mounted on the inner front wing, on the Range Rover it is located on the chassis forward of the fuel tank. An arrow on the filter shows the direction of the flow.


The amount of fuel delivered depends on two parameters: Opening time of the injectors and the fuel pressure. To ensure that the required amount of fuel is injected is only dependend on the opening time of the injectors it is very important the fuel is delivered at a constant pressure difference with the manifold pressure.

When the fuel pressure is low the spring holds the valve against the fuel return pipe and no fuel flows back to the tank. Under low manifold depressions......Full throttle!! There is also a great need for fuel from the engine and so no fuel will drain back into the tank. This is important because with high manifold pressures fuel is sucked in more easily from the nozzle. To ensure an equal amount of fuel is injected the fuel pressure therefore needs to be reduced depending on the manifold pressure.

When the manifold pressure is high.....idling or overrun...the diapragm valve is drawn against the spring and fuel is drained back into the tank. Fuel pressure drops consequently and prevents to much fuel being sucked in.


Fuel pressure regulator 3,7 kB
There are eight of these little beauties on your Rover..... No single point injection here!! The injectors are needle valves which are opened by the electrical solenoid. When current is flowing through the coil the valve opens against the spring pressure. The duration time which the injector is open is determined by the ECU. The injectors don't operate one after the other. They are switched in two banks. The injectors on the right cylinder bank are numbered 1, 3, 5, 7 The left bank accordingly 2, 4, 6, 8. All injectors of one bank inject simultanuously. When loosening the connectors on these parts, be careful because the connectors tend to become very brittle with age. When uprating your engine it should be checked if your injectors have enough capacity.... otherwise you have to install bigger sized injectors.


Injector 5,2 kB

The resistors are connected in series with every injector and reduce the 12V Voltage to 3V, measured over the injectors when they are energised.


The cold start injector

This injector is located in the top of the plenum chamber. As its name indicates it injects additional fuel when the engine is cold and the engine is being cranked. The cold start injector injects continuously and not intermittently like the other injectors. The injector gets its signal directly from the Thermo Time Switch and is not switched or controlled by the ECU.


The thermo time switch controls the operation of the cold start injector. It is basically a pair of contact points, one of which is mounted on a bi-metal strip. A heater coil is fitted around the strip. The system works when the ignition switch is in the "crank" position. Whenever the bi-metal is cold the points are closed and the injector is operated. During the time the contacts are closed the current is heating up the strip. After max.12 secs (depending on ambient temperature) the bi-metal opens the points and injection stops. When the engine is already hot the bi-metal strip prevents the injector to operate during cranking. Notice that the extra air valve uses the same basic principle of a heated bi-metal strip.


Thermo-time switch 2,1 kB
This sensor is located at the front of the inlet manifold in the coolant gallery.It can be mistaken for the Thermotime switch but this one is less bulkier. It gives a signal to the ECU for engine temperature so that the ECU can inject more or less fuel depending on engine temperature. It does not affect the cold start injector!


Coolant temperature sensor 1,1 kB
The Extra Air valve allows additional air to by pass the Throttle butterfly. This is giving the engine a somewhat higher rpm on idle when the engine is cold. This to prevent a stalling engine. When the fuel pump is running current will be passing through a heating coil in the valve. The bi-metal is heated and slowly closes the valve. Once the valve has closed the heat generated by the engine itself will ensure it does not open again until the engine has cooled down. On worn egines this valve can sometimes stick because of oil residues, resulting in difficult starting because the engine won't idle properly. The coil is connected to terminal 87 of the fuel pump relay and earthed at pin 34 of the ECU. In the next picture you can see how the pipe connections to the EAV run.

Plenumpiping 3,9 kB


Extra air valve 4,1 kB
This screw controls a by pass over the Throttle valve. By passing more air around the throttle butterfly the engines rpm increase when idling. It can be set with a simple screwdriver and changing the setting does not have any effect on CO


The CO screw

This screw lets you bypass more or less air without the airflow meter measuring it. If you bypass more air without injecting more fuel your mixture will be leaner, thus giving a lower CO reading. Be careful with setting the CO level too low. The mixture can get lean resulting in an overheating engine. Good results for checking your CO level can be had by installing a colortune plug. This plug is transparant and gives you a look into the combustion chamber. By turning the CO screw you can directly see which effect it has.


The Throttle potentiometer

The position of the throttle butterfly and its rate of movement is detected by a potentiometer connected to the pivot axis of the butterfly. The potentiometer then gives its signal to the ECU. The position of the potentiometer is adjustable. To set it properly:

  • ignition on
  • connect Voltmeter (setting on 10V!! not higher) between red and green leads
  • Reading should be 325 +/- 35 mV
  • If incorrect slacken the two screws and turn potentiometer
  • tighten screws and recheck voltmeter

The Air Flow Meter

The air flow meter is together with the ECU one of the most important parts of the injection system that is why we've got a separate page for it here. Defenitely recommended


The Electronic Control Unit (ECU)

The brains of your V-8!! All the data from the sensors and the airflow meter are fed into this little black box. Then it computes how long and how fast the injectors have to do their work....inject! Interested in the functioning of this device??..... check out this page! It's worth it


The distributor sends a signal to the ECU. From this signal the ECU knows the engine speed and is able to calculate when the injectors must inject. Being an 8 cyl. engine the ignition reluctor inside the distributor has off course eight 'points'. Only four are used to signal inject. Remember that the injectors are switched on/off simultaneously in two banks!. So for every revolution of the distributor every injector injects two times. Because the distributor turns at half the speed of the engine this means that every injector injects one time per revolution of the crank.

Strange isn't it?? one injection per revolution.....We have a four stroke so there is one spark for every two revolutions of the crank....but two injections?! Well besides avoiding a costly split into four banks of two injectors, this solution is also chosen to give the fuel time to evaporate properly. Furthermore the injector size can be smaller and reactions on changing conditions are just that bit faster


The distributor 2,4 kB
Well unless you have a diesel engine it won't go an inch without electrics.....and this is even more so if your carriage is equipped with injection. So it is very wise to keep this box in tip-top shape. If the voltage drops the injector current is also declining. This means less fuel being injected. To compensate for this the ECU makes sure the total amount of fuel injected is independend of the system voltage. This is done by increasing the duration of injection when the Voltage drops, Look up the ECU info for a more detailed description




SD1 injection......The airflow Meter     SD1 injection......The ECU

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