Contents: Visual inspection of fuel injection… ↳ Determining the location of a leak… ↳ Checking the idle speed ↳
As already noted, the majority of repair and maintenance work on the fuel injection system must be carried out at a service station. Only a specialist has special control and measuring devices and the relevant knowledge. In case of damage to the electronic engine control units, various tests must be carried out in a strictly defined sequence to identify defects. This is the only way to prevent damage to electronic components and eliminate indirect damage that leads to expensive repairs. However, it should be borne in mind that faults in the electronic control units of the Fiesta are very rare.
Visual inspection of fuel injection system components
Check the condition and tightness of the following hoses from time to time.
1. Vacuum hose connected to the absolute pressure sensor.
2. Vacuum hose connected to the brake booster.
3. Condition of the crankcase ventilation hoses. Make sure that the hoses are not clogged, dirty or swollen.
4. Reliability of fastening of fuel lines.
5. Reliability of the pressure regulator connection.
6. Fuel return line from the pressure regulator.
Fig. 8.9. Locations for checking the reliability of the connection of the contacts of the EVR valve (1), EVAP valve (2) and DPFE sensor (3) connectors
7. When working in the engine compartment, it is necessary to disconnect various connectors, which may result in the contact connections becoming loose. If this happens, spray the contacts with a special aerosol for contacts and, if this does not help, carefully bend the contacts (Fig. 8.9).
Determining the location of a leak in the air intake system
A leak in the air intake system results in additional air entering the engine. This interferes with the operation of the control unit and causes erroneous results, for example, when preparing the fuel mixture: the injectors supply less fuel to the engine, which leads to a leaner fuel mixture. This is most clearly determined by a change in the engine crankshaft speed at idle.
SEQUENCE OF WORKS
1. Check the vacuum hose for cracks and the reliability of its fastening. Check the condition and reliability of fastening of all hoses that are connected to the throttle assembly and intake manifold (absolute pressure sensor, brake booster, fuel mixture preparation system, etc.).
2. Start the engine and let it idle. Open the hood and disconnect the connector from the oxygen sensor.
3. Spray standard cold engine starting spray onto the injection system components, all hose connections and gaskets one by one. The place where the engine speed increases when spraying the spray is a leak.
Checking the idle speed
The idle speed is constantly adjusted by the control unit and the idle actuator motor depending on the switched-on consumer, such as headlights, air conditioning or power steering (when turning the steering wheel). The idle speed of the crankshaft for gasoline engines of the Fiesta is 900 min⁻¹, for diesel engines - 850 min⁻¹. To check the idle speed, you must use an accurate tachometer or engine tester. If the idle speed does not correspond to the required values, it cannot be adjusted separately, it is necessary to determine the malfunction in the engine. For example, if the wires were disconnected from the battery terminals, the engine control unit must spend some time on the road to restore the engine control modes.
For more information, please visit the website: FORDBOOK