5.5.5. Fuel supply
TNVD of distributive type
Fig. 4.88. Supply of fuel at distributive TNVD: 1 – fuel tank; 2 – fuel heat exchanger; 3 – heated fuel; 4 – fuel filter of rough cleaning; 5 – fuel filter of thin cleaning; 6 – pump of high pressure; 7 – fuel on nozzles; 8 – nozzles; 9 – return fuel-supply line
|
The fuel pump at TNVD of distributive type soaks up fuel via the fuel heat exchanger and the fuel filter (fig. 4.88). For removal of air the throttle serves in a pump casing. For reliable work of diesel fuel in winter conditions (it is, as a rule, air temperature to –25 °C) it heats up previously. The system of heating consists of the fuel heat exchanger with the thermostat on a head of cylinders. The thermostat works as follows: full heating — if fuel temperature to +18 °C, the mixed mode — from + 18 to + 30 °C (fuel temperature).
The fuel filter consists of the metal case in which the paper filter is inserted (with very small time). The filter of rough cleaning is located sideways.
The fuel pump is bladed the pump which is built in TNVD. The casing of the pump is located eccentric to a drive shaft. Volume under blades is not identical. The largest volume of fuel arrives through an entrance opening. Fuel is forced out in the output union by the pump blade. If the motor rotates with a speed more than 5000 min.-1, then giving pressure by means of the valve of adjustment of pressure with pistons and springs is limited approximately on 8 bars. Pressure of giving has to be as the highest, and constants that various hydraulic knots of the pump were correctly supplied. At start of the engine air independently is removed from a fuel supply system thanks to operation of the pump and a throttle. At start of the engine the starter has to rotate without interruption, the engine will not be started yet, otherwise there will be no production of air.
Line TNVD
Fig. 4.89. Supply of fuel at line TNVD: 1 – fuel tank; 2 – fuel heat exchanger; 3 – heated fuel; 4 – fuel filter of rough cleaning; 5 – fuel filter of thin cleaning; 6 – TNVD; 7 – electrohydraulic switch (ERE); 8 – fuel pump; 9 – a throttle with the returnable valve; 10 – fuel lath (ERE); 11 – pipeline of high pressure; 12 – nozzle; 13 – return fuel-supply line
|
The fuel pump is installed on flanges (fig. 4.89). It soaks up fuel via the fuel heat exchanger and the fuel filter. For removal of air the throttle with the returnable valve serves in a zone of absorption of TNVD.
PREVENTION
Treatment of fuel
It is dangerous to work with fuel. Therefore work carefully if you serve or you repair a fuel supply system. Be especially careful at plum of fuel from a tank.
1. Disconnect the accumulator, be convinced that cables cannot concern accumulator poles.
2. Merge fuel from a tank not indoors. For this purpose you need the corresponding device (for example, a hose with the contracting pear). Do not merge fuel through an opening of the sensor of a reserve of fuel at all or sucking away fuel a mouth through a hose — poisoning with highly toxic additives is possible.
3. Near at hand there has to be a carbon dioxide or foamy fire extinguisher.
4. Do not merge fuel in a hole. The gases which are emitted from fuel it is heavier than air and will accumulate at the bottom of a hole. Consequences: poisoning with gases and danger of explosion.
5. Make sure that in a zone and near a zone of work there are no switched-on electric devices, the dug-out fire, sources of heat and sparks.
6. Merge fuel in densely closed special capacity with protection against ignition and the valve of alignment of pressure.
7. In the merged tank there are fuel vapors. They are also very dangerous. Therefore work with extra care.
|
The system of preliminary heating of fuel turns on the fuel heat exchanger with the thermostat installed on a head of the block of cylinders. For reliable work of diesel fuel in winter conditions it has to be previously heated. The thermostat works as follows: full heating — if fuel temperature to + 18 °C, the mixed mode — from + 18 to + 30 °C. The fuel filter consists of the metal case in which the paper filter is inserted.
Check of a fuel supply system on tightness
If in a zone of the parking of the car smells of diesel fuel, so fuel somewhere comes to light. For search of leaky connections deliver to Mercedes for the night on the parking on the dry, pure place.
SEQUENCE OF WORKS
|
"30 000 km"
1. Check whether spots under the car appeared.
2. If there are no spots, start the engine and let's it work several minutes.
3. Kill the engine. Again check whether spots appeared.
4. If there are no spots, check all tubes and knots of a fuel supply system for a characteristic smell of diesel fuel.