A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ System of an exhaust
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and channels of absorption
- System of injection
+ System of injection of Motronic
- System of injection of MPI and MPFI
Additional functions
Knots of system of injection
Functioning
Adjustment with the help a lambda probe
Violations in work and self-diagnostics
Self-help
Visual control
Check of knots
Dismantle of separate details
Cable of a butterfly valve
Inlet collector
Idling adjustment
Check of exhaust gases
The help at malfunctions
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ System of ignition
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics
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Check of knots
In the following sections checks of elements of system of injection, possible with use of amateur means are described.
Injection valves
If there is a suspicion that one of valves of injection does not function, you can easily find out it by means of the LED indicator of tension and an exact ohmmeter.
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- Dismantle an engine cover.
- Disconnect sockets of valves of injection.
- In the beginning check of tension: connect the LED indicator of tension (not a control lamp) to contacts of the socket. Start the engine: the light-emitting diode in the indicator of tension has to flash if is not present, then tension does not move or the control unit connecting weight is faulty. This inspection cannot be carried out the measuring device.
- Check of resistance: disconnect sockets of valves of injection, connect an ohmmeter to both contacts of the valve: if the engine cold, the device shows 13,5–17 Ohms.
- If size is not tolerant, replace the valve (if measurement was taken precisely).
- Tightness check: dismantle a distributive tube of fuel together with injection valves.
- Sockets of valves of injection are disconnected, fuel-supply lines remain connected.
- Let your assistant several times will turn the engine a starter in order that earned the fuel pump and there was fuel pressure.
- Observe injection valves: each of them has to let out at most 1-2 drops of fuel a minute. Otherwise replace the corresponding valve.
- Irrespective of it it is possible to check a stream of injection and amount of the fuel injected by the valve if it is necessary because of violations in operation of the engine.
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Potentiometer of a butterfly valve
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- Disconnect the socket of a potentiometer of a butterfly valve.
- Measure by an exact ohmmeter resistance between contacts of a potentiometer.
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Provision of a butterfly valve
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Measurement between contacts
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Nominal size (kOhm)
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| Does not matter |
1 and 2
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1,5–2,6
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| Idling |
2 and 3
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0,75–1,3
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| Full gas |
2 and 3
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at most 3,6
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Having disconnected the socket (1), it is possible to measure giving of tension on valves of injection (2) by means of the LED indicator of tension. When the engine is turned by a starter, light-emitting diodes in the indicator of tension have to flash. If is not present, then tension does not move. |
Measuring instrument of mass of air
Only MPI
On the right: in the photo are shown the measuring instrument of mass of air (1) engine with a working volume of 2,8 l and the triple-pole socket (2).
At the left: the scheme of an arrangement of contacts of the triple-pole socket is used for check of the measuring instrument of mass of air.
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- Measurements are performed at a butterfly valve in the situation "idling" and "full gas" at the idle engine.
- The following nominal sizes have to be received:
- Shift a rubber tip on the socket of the measuring instrument of mass of air back, the socket remains connected.
- Connect the exact voltmeter to contacts of the socket behind as it is described below:
- Measurement 1: connect measuring wires to contacts "2" and "3".
- Include ignition.
- The voltmeter has to show 12–14 Century. If is not present, then defect in giving of tension.
- Check a safety lock 32 if it is necessary, check a wire from a safety lock 32 to contact "3" sockets of the measuring instrument of mass of air.
- Or check connection from the mass of the engine to contact "2".
- Measurement 2: connect measuring wires to contacts "1" and "2".
- Include ignition.
- The voltmeter has to show 0,3–1,1 Century.
- Start the engine (the wire remains connected). Switch off everything consumers, the fan of a radiator should not work
- l Consistently force to hesitate engine turns between idling and 4000 rpm.
- The voltmeter has to show (depending on number of turns) from 1,5 to at most 3,4 Century. If is not present, then the measuring instrument of mass of air is faulty. Replace it.
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Idling stabilization valve
Only MPI
With a working volume of 2,8 l the valve of stabilization of idling is in the engine on the right on a branch pipe of a butterfly valve.
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- Disconnect the socket of the valve of stabilization of idling and connect an exact ohmmeter to both contacts of the socket of the valve.
- The measuring device has to show 7–11 Ohms, otherwise the valve is faulty.
- Deeper check of working capacity: dismantle the idling stabilization valve; the socket remains connected.
- Put a rotor in air pass of the valve in situation "is open" or "closed" (do not use the metal tool for this purpose).
- Include ignition and observe a rotor: it has to fluctuate approximately on average situation.
- Check ease of the course of a rotor: it has to move due to the tolchkoobrazny movement of the dismantled valve.
- Besides, on it there should not be jags or attritions.
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Idling stabilization valve
Only MPFI
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In the photo the valve of stabilization of idling (shooter) in the engine with a working volume of 2,6 l is shown. |
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The valve of stabilization of idling (1) with a working volume of 2,8 l is in the six-cylinder engine near the regulator of pressure of fuel (2) as you can see in this photo. |
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Attention! The valve of stabilization of idling of the engine with a working volume of 2,6 l cannot be dismantled in a house workshop as right after installation so-called main adjustment of system of injection has to be carried out that it is possible to make only by means of the device for reading of malfunctions of V.A.G 1551 in Audi workshop.
If the socket on the valve of stabilization of idling is disconnected within 1/2 hours after the last switching off of the engine, malfunction "defect of the valve of stabilization of idling" will be kept in memory of the computer (that, maybe, was not made before). |
In this valve only the winding is checked:
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- Disconnect the socket on the idling stabilization valve.
- Measure by an exact ohmmeter resistance between contacts of the 1 and 4 socket, and also "2" and "3" valves.
- If the valve in working order, the device has to show 45–60 Ohms, otherwise the valve should be considered defective.
- Other inspections by own efforts cannot be carried out.
- If the workshop replaces the valve, at once carries out the mentioned main adjustment.
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Sensor of temperature of cooling liquid of system of ignition/injection
At the left: behind on the engine screwed up in a tube of supply of cooling liquid there is a combined sensor of temperature of cooling liquid (1) system of ignition/injection and the indicator of temperature. Here the socket (2) is disconnected for check of the sensor. Contacts of the 1 and 3 socket belong to system of injection.
On the right: the chart shows, at what temperature what size of resistance this sensor has to show.
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Attention! If the socket on the sensor of temperature of cooling liquid in the engine with a working volume of 2,6 l is disconnected within 1/2 hours after the last switching off of the engine, malfunction "defect of the sensor of temperature of cooling liquid" will be kept in memory of the computer (that, maybe, was not made before). |
General provision: the reason can be in the sensor of temperature of cooling liquid if in the certain ranges of temperature there are shortcomings of operation of the engine. Check:
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- Disconnect the socket on the sensor of temperature of cooling liquid.
- Measure by an ohmmeter resistance between contacts of the 1 and 3 socket of the sensor.
- The measured resistance is compared depending on engine temperature to the chart of nominal size below. If size is at considerable distance out of curves, replace temperature sensor.
- In summary here it is necessary to call two more approximate sizes of resistance: at a temperature of cooling liquid of 20 °C the ohmmeter has to show about 2,5 kOhm, at 80 °C – about 330 Ohms.
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The sensor of temperature of the soaked-up air
Only MPFI
On the right: the sensor of temperature of the soaked-up air (3) is only in the engine with a working volume of 2,6 l. It is on the right behind on the engine near the valve of stabilization of idling (1) and the regulator of pressure of fuel (2).
At the left: on this chart sensor resistance size depending on temperature of the soaked-up air is shown.
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Attention! If the socket on the sensor of temperature of the soaked-up air is disconnected within 1,5 hours after the last switching off of the engine, malfunction "defect of the sensor of temperature of the soaked-up air" will be kept in memory of the computer (that, maybe, was not made before). |
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- Disconnect the socket of the sensor of temperature of the soaked-up air.
- Measure by an exact ohmmeter resistance between two contacts of the socket of the sensor.
- Compare the measured resistance depending on engine temperature to nominal size in the chart below. If size is at considerable distance out of curves, replace temperature sensor.
- In summary here the approximate size of resistance is specified: at 20 °C (room temperature, the engine cold) the device has to show about 6,3 kOhm.
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