Checking and adjusting the GM «Multec SPI» fuel injection system (Opel Kadett E)

Checking the engine idle speed

The engine crankshaft speed at idle is maintained automatically within 720-880 rpm by the idle speed regulator in response to commands from the electronic control unit (ECU). The carbon monoxide (CO) content in the exhaust gases, which should be less than 0.4%, is automatically regulated by the ECU based on information from the oxygen concentration sensor in the exhaust gases. Thus, neither the idle speed mode nor the CO content need to be adjusted during operation.

The engine idle speed test is performed on an engine warmed up to normal operating temperature, with the spark plug electrode gap and ignition timing correctly set, with an installed air filter with a clean filter element, with a fully charged battery in good condition, and with all current consumers switched off.

If the idle speed is not within the norm, check the operation of the idle speed control valve.

If the CO content does not correspond to the required value, check the tightness of the engine air supply system, the serviceability of the system elements and electrical circuits.

Checking the throttle opening

The throttle valve opening is set at the factory and cannot be adjusted during operation.

Note: During operation, it is prohibited to change the position of the idle speed adjustment screw, located on the top of the throttle body next to the idle speed regulator (see picture).

Checking the fuel supply pressure

[Original article on the web portal: opelbook.ru]

Make sure the ignition is off. Disconnect the fuel pump relay connector. Crank the engine with the starter for less than 5 seconds to relieve pressure in the injection system.

Attach the pressure gauge to hose 1 (see picture) fuel supply through a tee.



Connect the fuel pump relay connector.

Start the engine at idle speed and check the fuel supply pressure using the pressure gauge, which should be within 0.7-0.8 kg/cm².



If the fuel supply pressure is below 0.6 kg/cm², check the serviceability of the fuel pump, fuel filter, fuel pressure regulator and fuel drain hose.

Checking the fuel pressure regulator

The fuel pressure regulator is installed in the injector body and is not subject to adjustment. Before removing the pressure regulator, relieve the pressure in the injection system. Each time the cover fastening screws are loosened or removed, replace the diaphragm 1 (see picture). Tighten the regulator cover mounting screws to a torque of 0.25 Nm.

Checking the throttle position sensor

Make sure the ignition is off. Disconnect the throttle position sensor connector.

Connect an ohmmeter to terminals "A" (black and white wire) and "B" (brown wire) sensor pads and measure the resistance, which should be within 4-9 kOhm.

Connect an ohmmeter to terminals "B" and "C" (blue wire), close the throttle valve and measure the resistance, which should be 1-3 kOhm.



Gradually opening the throttle valve, monitor the resistance, which should smoothly increase to 5-10 kOhm with the throttle valve fully open.



Connect the voltmeter to terminals "A" and "C" of the sensor block.

Turn on the ignition and check the sensor supply voltage with a voltmeter, which should be within 4.7-5.1 V. If the voltage is not normal, check the circuit between the sensor connector and the ECU terminals.

Checking the vacuum sensor

Check the vacuum hose connecting the intake manifold to the vacuum sensor for sharp bends, cracks, or blockages. If necessary, repair or replace the hose.

Make sure the ignition is off. Without disconnecting the sensor connector, connect the voltmeter to the terminals "C" (black and white wire) and "A" (brown wire).



Disconnect the vacuum hose from the sensor block.

Turn on the ignition and check the voltage using a voltmeter, which should be within 4.7-5.1 V, then turn off the ignition.

Connect the voltmeter to the "B" terminals (green wire) and "A" (brown wire) sensor pads. Connect the vacuum hose to the sensor. Disconnect the vacuum hose from the inlet pipe, connect the vacuum pump to the hose and the pipe fitting.

Turn on the ignition and, creating a pressure of 0.2, 0.6 and 0.8 kg/cm² in the sensor using the pump, check the voltage using a voltmeter, which should be within 3.5-3.9, 1.3-1.7 and 0.3-0.7 V, respectively.



If the voltage values do not match the data, check the wires and their connections between the sensor and the ECU. After checking, connect the vacuum hose to the intake manifold.

Checking the coolant temperature sensor

Make sure the ignition is off. Disconnect the coolant temperature sensor connector. Release residual pressure in the engine cooling system. Unscrew the sensor.

Place the sensor in a tank with water or coolant that can be heated. Turn on the water heating and measure the resistance of the sensor at different temperatures in the tank, which should correspond to the values specified in the subsection "Design and technical characteristics"

After checking, put the sensor back in place and connect the connector to it.

Note: The coolant temperature sensor can be tested on the engine at the appropriate coolant temperature.

Checking the idle speed control valve

To check the regulator on a vehicle, do the following:

• make sure the ignition is off;
• disconnect the regulator connector;
• connect an ohmmeter to terminals "A" and "B" of the connector and measure the resistance, which should be 50-65 Ohms;
• connect an ohmmeter to terminals "C" and "D" and measure the resistance, which should be within the same limits.

Connect an ohmmeter between the regulator body and each of its terminals in turn. In both cases, the ohmmeter should show R=∞.



The removed regulator is checked as follows:

• connect the regulator connector;
• turn on the ignition;
• lightly pressing on the end of the head of valve 1 (see picture), check the smoothness of its movement.

If the regulator does not meet any of the listed requirements, it must be replaced. Before installing the regulator, measure the distance between the end of the valve head and the mating surface of the regulator, which must be at least 28 mm.

Checking the injection nozzle

Remove the air filter. Make sure the ignition is off.

Disconnect the injector connector, connect an ohmmeter to its terminals and check the winding resistance, which on a cold engine should be within 1.4-1.8 Ohm. When measuring on a hot engine 5 minutes after stopping, the resistance of the injector winding should be 1.6-2.0 Ohm. After checking, connect the injector connector and put the air filter back in place.



The fuel spray cone and injector tightness are checked as specified in the subsection "Fuel injection system "LE-Jetronic"".

Checking the oxygen concentration sensor in the exhaust gases

Make sure the ignition is off. Disconnect connector 1 (see picture) sensor and connect a voltmeter to its terminals.



Turn on the ignition. The voltage on the voltmeter should be within 0.30-0.55 V.

If the voltage does not match this value, check the integrity of the circuit between the ECU and the sensor.

Connect the voltmeter to the sensor block and to ground.

Start the engine and allow it to run at a crankshaft speed of 1300 rpm to warm up the sensor, then switch the engine to idle speed. In this case, the voltage on the voltmeter should vary within 0.05-0.95 V.

Briefly increase the engine crankshaft speed: the voltage on the voltmeter should be 0.7 V.

If the sensor does not meet the specified requirements, it must be replaced.