Checking the single-point injection system (Renault 19)

Self-check

Many types of injection system testing are not available to amateur motorists, as they cannot be done without the necessary control and measuring instruments.

The control device cannot be tested at home. In practice, this device is very rarely faulty.

Sensors, switches and wire connections are much more likely to fail. Therefore, if there is a malfunction, it is advisable to proceed as follows:

1. Make sure the ignition is OK.

2. Check the power supply system.

3. Conduct an external inspection of the injection system components.

4. If you are unable to detect the fault in this way, study the "Troubleshooting" table at the end of the chapter or have the injection system checked at a workshop that has all the necessary equipment.

Visual inspection check

1. Are the engine ventilation air hoses clogged, dirty or swollen?

2. Are there any signs of fuel leakage on the fuel lines?

3. Check the pressure regulator for leaks.

4. Check the return flow of fuel from the pressure regulator.

5. Is the injector gasket damaged?

6. Have the wire connectors been disconnected and reconnected repeatedly? Corrosion or improper connection may be the cause of poor contact.



7. Carefully inspect the contact connections in individual elements of the injection system design. Do not bend the contacts, but only treat them with a special cleaning aerosol.

Search for leaks

A leak in the intake system allows so-called "erroneous" air to enter, i.e. air that is not taken into account in the control device's calculations and that disrupts the preparation of the combustible mixture. As a result, the working mixture becomes uncontrollably leaner. The easiest way to recognize this malfunction is at idle by fluctuating engine speed.

1. Check the low-pressure hoses for cracks and tightness of connection with the pipes. It is necessary to check all hoses that are connected to the injection system or to the intake manifold (pressure sensor, brake booster, intake air preheater, fuel mixture preparation system).

2. Warm up the engine and, leaving it idling, open the hood.

3. Spray the launch fuel spray (for example, " launch pilot" "Startpilot") injection device in the flange to the intake manifold, gaskets between the flanges of the intake channels and pipelines to the controlled reduced pressure housings (in order to disconnect the lambda probe connector).

4. If the engine speed changes when processing a certain area, it means that there is a leak there.

Checking individual elements

Below is a description of how to check individual elements of the injection system at home.

Recommendation: When working on the injection system, you should remember that the system remains under pressure for a long time after the engine is turned off. Therefore, always have a rag ready when unscrewing bolts and pipes to prevent gasoline from splashing.

Checking the throttle position controller

• Disconnect the connector from the throttle position controller.
• Bendix servo motor: to pin "2" (counted from left to right) connect the "ground" and 12 V to contact "3".
• Bosch servo motor: connect a maximum of 6 V to both upper connection contacts of the servo motor (for example, using a 4.5V battery); "–" minus up.
• Both motors: The pushrod should extend fully.
• Change the poles of the connecting wire.
• The plunger should retract fully.
• If everything happens as described, then the throttle position controller is working properly. If not, it needs to be replaced.

Left: On the Bendix single-point injection system, opposite the idle speed limiter for the throttle valve (2) is the limiter for the full-load switch (1). The adjustment of the tappet (3) of the throttle positioner (4) must be carried out in a workshop. Right: Here it is the same for the Bosch single-point injection system: opposite the idle speed limiter (1) of the throttle valve is the limiter (2) of the tappet (3) of the throttle positioner (4). After disconnecting the contact connection (5), the engine operation must be checked.

Checking the functionality of the idle switch

• Disconnect the throttle position controller connector.
• Bendix servo motor: Connect an ohmmeter to the servo motor terminals.
• The resistance with the pusher contact disconnected should be 5 kOhm.
• With the pusher contact connected, the resistance should be 0.15 ohms.
• Bosch servo motor: Connect an ohmmeter to the idle switch terminals.
• For this purpose, use contacts "1" and "2" on the five- and seven-pin connector, counting from the right.
• Idle switch pressed: resistance 0 ohms.
• Idle switch not pressed: resistance tends to infinity.

Testing the Bendix Full Load Switch Regulator

• Disconnect the switch connector.
• When the switch is closed, the resistance should tend to infinity.
• In the maximum fuel supply position (pressed switch) the resistance should be 0.15 Ohm.

Checking the throttle potentiometer of the Bosch injection system

• Disconnect the throttle potentiometer connector.
• According to the table, connect the ohmmeter to the two contacts indicated.
• If the specified values are not achieved, the throttle potentiometer is faulty. It cannot be replaced separately. The lower part of the injection system housing must be completely replaced.

terminals		Verification conditions	Resistance
Manual transmission	Automatic transmission
1 + 5	1 + 7	—	520—1300 OHM
1 + 2	1 + 2	From fully closed to 1/4 throttle position: resistance increases, then becomes constant.	600—3500 ohms
1 + 4	1 + 6	From fully closed to 1/4 throttle position: resistance then increases.	600—6600 ohms

Checking the injector

1. Disconnect the pipes and remove the air filter.

2. Start the warm engine and let it idle.

3. Look at the fuel stream from the injector. It should be uniform and directed towards the throttle valve.

4. Stop the engine to check the valve for leaks.

5. When the engine is not running, no more than 2 drops of fuel per minute can flow out of the injector.

6. You carry out further testing if the engine fails to start.

7. Check the electrical relay of the system.

8. Disconnect the pipes and remove the air filter.

9. Turn the engine over with the starter.

10. You should see the injector injecting fuel.

11. If not, disconnect the connectors on top of the injection system.

12. Connect the ohmmeter to both connecting contacts.

13. At an ambient temperature between +15°C and 30°C, the resistance should be about 1.2 Ohm (Bosch) and 1.4 Ohm (Bendix), otherwise the injector is faulty. Unscrew the TORX bolt and replace the injector.

14. Check for contact in the electrical circuit of the injector if it does not inject fuel despite the required resistance.

15. Connect the LED voltage tester, without using any other devices, to both contacts on the removed connector.

16. Turn on the starter: the LED should blink; if not, then there is a break in the wire somewhere or the control device is faulty.

Checking the fuel supply cut-off during engine braking

1. Disconnect the pipes and remove the air filter.

2. Start the engine, let it run for a while at over 3000 rpm and close the throttle valve sharply.



3. At this point, the fuel flow from the injector should be interrupted for a short time. In this case, everything works fine.

4. If not, check the throttle switch and control unit yourself or at a car repair shop.

Checking temperature sensors

1. Intake air temperature sensor (bosch throttle body): Disconnect the connector from the top of the injection system.

2. Connect an ohmmeter to both contacts.

3. Coolant temperature sensor (type "F" engine) or intake manifold temperature sensor (type "C" engine): Disconnect the connector from the two-pole sensor.

4. Connect an ohmmeter to the sensor contacts.

5. Both types of sensor: determine the resistance value and compare it with the table below.

6. If the measurement results match the data in the table, the sensor is working normally.

7. Coolant temperature sensor or intake manifold temperature sensor and mixture temperature sensor: expose the "+" contact of the sensor (wire color, see. Electrical diagrams). The pin header remains on.

8. Connect the voltmeter: place the thin test tip on the bare contact, and connect the other to ground.

9. Start the cold engine and let it warm up.

10. Observe the voltmeter arrow - the value should constantly increase.

11. If the arrow does not move, the temperature sensor is faulty.

Temperature measurement	0±1°C	20±1°C	40±1°C	80±1°C	90±1°C
Intake Air Temperature Sensor 1.8L Engine	5.29—6.49 kOhm	2.4—2.6 kOhm	1.07—1.27 kOhm	—	—
Mixture temperature sensor 1.4-/1.7-liter engine	7.47—11.97 kOhm	3.06—4.04 kOhm	1.29—1.65 kOhm	—	—
Intake Manifold Temperature Sensor 1.4L Engine	—	3.06—4.04 kOhm	1.31—1.60 kOhm	0.30—0.37 kOhm	0.21—0.27 kOhm
Coolant Temperature Sensor 1.7-/1.8L Engine	—	3.06—4.04 kOhm	1.31—1.60 kOhm	0.30—0.37 kOhm	0.21—0.27 kOhm

Checking fuel pressure

1. Fuel pressure can only be accurately determined using a special measuring device (in the auto repair shop).

2. If you suspect incorrect fuel pressure, disassemble the pressure regulator: unscrew the 4 TORX bolts (bolt with rolled thread for socket, star key).

3. Check if the membrane is damaged or if dirt has accumulated.