The Rover V-8 EFI system is very sensible for leaking vacuum connections which can result in a bad idling and/or a rough running engine. Therefore carefully inspect all the vacuum pipes for leakage and check the conditions of the clamps!. On the SD1 most piping is at least 13 years old by now so the rubber can be hardened or become porous.

An indication for a vacuum leak can be noticed because the engine is running rough on idling and low rpm. The rough running then slowly disappears with increasing rpm. This can be explained because at idle and low rpm the throttle valve is almost closed. This gives a high vacuum in the plenum chamber and thus a high vacuum in the vacuum piping. So a lot of outside air is sucked in directly instead of going through the air flow meter, as a result the air/fuel mixture is too lean resulting in a poor running engine, and yes..those white noses on your plugs. With wider throttle openings the vacuum becomes less and thus less air is leaking in.

A simple test if you have a rough running engine at low rpm is to disconnect the filter and manually (with a screwdriver for instance) open the flap of the airflow meter a bit with the engine idling. This way you make the EFI system injecting more fuel. If the engine starts to run smooth there is almost certainly a leakage in your vacuum piping.

Excessive fuel consumption and black smoke can be caused by a perforated diaphragm from the fuel pressure regulator. To check this remove the vacuum pipe. If there is fuel coming out of the regulator's vacuum connection, the diaphragm is at fault and the regulator should be replaced.

If the problem wasn't in the hose connections or in the ignition then the following tests can help you locating the fault in your EFI system.

The reading should be 11 to 12.5 Volts

If below 11 Volts or 0 Volts check:

• State of the battery
• Earth connections
• Positive connections to main relay (Brown wire (N))

The reading should be 0 Volts
If above 0 Volts renew the main relay

Turn ignition ON
Main relay can be heard by a click and voltmeter should read 11 to 12.5 Volts If below 11 Volts or 0 Volts check:

• All the white wire connections (W) to the relays and steering module
• Earth connections at terminal 86 and both relays
• Good connection of brown&orange wire (NO) at main relay terminal 87
• Good connection of blue&yellow wire (UY) at main relay terminal 87 and ECU pin 10.

If OK continue with Test 3

Manually open the flap of the meter.
Listen for the fuel pump and relay operation.
Voltmeter should read 11 to 12,5 Volts

If below 11 Volts check:

• All wiring connections as shown in this diagram.

If the voltmeter reads correctly but the relay or pump don't operate
Subsitute steering module and then pump relay.

If pump still isn't operating
Suspect a faulty fuel pump.

If OK continue with Test 4

Ignition ON and cranking
The reading should be 8 to 12 Volts

If no reading but the starter motor operates check:

• White&red (WR) wiring
• connections to ECU pin 4 via the steering module and the wiring loom multiplug.

• Battery and starter motor

• Black & orange (BO) wiring, connections and starter circuit

Ignition ON
Listen for operation of fuel shut-off relay

If relay does not operate check:

• White wiring (W) and connections
• earth connection 86 from relay
• the vacuum switch and the connection hose, subsitute if necessary

If higher than 9 Volts or lower than 6 than check:

• electronic ignition system

Ignition ON
Listen for operation of fuel shut-off relay

If relay does not operate check:

• White wiring (W) and connections
• earth connection 86 from relay
• the vacuum switch and the connection hose, subsitute if necessary

If higher than 9 Volts or lower than 6 than check:

• electronic ignition system

Air flow meter flap closed. The voltmeter should read 1.55 +/- 0.1 Volts

If reading is incorrect

• peel back the rubber covering at the flow meter and connect voltmeter to terminals 8 and 9
• Measure readings again

If OK leave the ECU connections exposed and continue with Test 7

Voltmeter should read 4.3 +/- 0.2 Volt.

If Voltmeter reads 0 check:

• All wiring and connections seen in the diagram above

If voltmeter reads lower check:

• The wiring for high resistance (corrosion)

The Voltage should gradually decrease to 1.6 +/- 0.1 Volts

If the results are not within the specifications the potentiometer is at fault. Take the cover of the air flow meter and check the potentiometer for corrosion, etc.

If OK refit the ECU multiplug cover and continue with Test 8

• Peel back rubber boot covering at airflow meter and repeat the test at the air flow plug and then at the air flow meter socket

• the potentiometer is at fault. Take the cover of the air flow meter and check the potentiometer for corrosion, etc.