The electric torch device (EFD) is designed to facilitate starting a cold engine at ambient temperatures up to -30 ° С

Conventionally, the system of an electric torch device can be divided into two interconnected ones: fuel and electric.

The fuel system also provides the dosage of diesel fuel for combustion.

EFU Kamaz Candle

It is connected to the engine fuel supply system.

The main element of the electric torch device is torch candles.

They are installed in the intake pipes of the engine so that a uniform supply of heated air and fuel vapors to all cylinders is ensured.

The body 1 of the flare candle (Fig. 1) is of a non-separable design, has a lower threaded part for screwing into the inlet pipeline and fixing it with a lock nut 6.

Heating element 2 is made in the form of a pin candle and is a metal casing, inside of which a spiral is pressed in a special filler.

The filler has good thermal conductivity and electrically insulates the coil from the casing.

The heating element heats the spark plug to operating temperature, which ensures the evaporation and ignition of diesel fuel.

Fuel comes from the power system to the fitting, where it is cleaned by filter 7, and then enters the annular cavity formed by the surface of the heating element and evaporator 5. The amount of fuel is dosed by jet 8.

To increase the evaporation surface, a three-dimensional mesh 4 is used, surrounded by a screen 3 with two rows of holes.

The screen protects the flame from being blown away by the air flow sucked into the engine cylinders.

The principle of operation of an electric torch device is as follows

Before starting the engine, an excess fuel pressure is created using a manual fuel priming pump, which is maintained by the fuel pump during the crankshaft cranking period.

The jet valve of the fine filter and the injection pump bypass valve, blocking the drain fuel lines, provide fuel supply to the flare candles 13 with a minimum time delay at a pressure of 20...40 kPa.

At this pressure, the minimum time for the formation of a flame is provided. Increasing or decreasing this pressure leads to a delay in the formation of a flame and, accordingly, to an increase in the start-up time.

The fuel passes through the solenoid valve 11 and enters the pre-heated torch candles, where it is dosed, heated and evaporated.

The ignition of the fuel and the formation of a flame torch occur due to the fact that at this moment the engine crankshaft is rotated by the starter and an air flow appears in the intake pipes, blowing the torch candles.

Particles of unburned fuel in the intake pipes in the form of vapors enter the cylinders together with heated air, where they ignite and contribute to the ignition of the main fuel injected through the nozzles.

To reduce the time for the engine to reach a stable mode, it is possible to combine its operation with the operation of an electric torch device. This ensures stable retention of the flame in the intake pipes when the engine is idling.

Technical characteristics of EFC products

Torch candle:

  • - rated voltage, V - 19
  • - current consumption at rated voltage, A 11-11.8
  • - fuel capacity, cm3/min 5.5-6.5

Thermal relay:

  • - rated voltage, V - 24
  • - rated current Ampere - 22.8
  • - time from the moment the current is turned on to the closing of contacts, s 50-65
  • - time of the closed state of the contacts after the current is turned off, s > 45

Solenoid valve:

  • - rated voltage, V - 24
  • - turn-on (open) voltage, V >12
  • - disconnection (closing) voltage, V >6
  • - current consumption at a voltage of 12 V, A <1.1

Wiring diagram

The EFU is powered by the vehicles batteries and includes torch candles 6 (Fig. 2), thermal relay 5, which is used to turn on the electromagnetic fuel valve 7, and the control lamp of the block 8, which indicates that the candles are sufficiently heated and power is supplied to solenoid valve; relay 4, designed to turn on the candles for maximum heating; relay 18 for turning off the excitation winding of the generator for a period of workoty EFU.

To activate the EFU, you need to press the button 14 of the remote start of the ground, then press the button 9 and hold it in this position until the lamp in block 8 lights up, then turn on the starter by turning the switch key 19 to the second position, without releasing the button 9.

The EFU is powered by batteries by turning on button 14 along the circuit: “+” batteries - starter terminals 17 - starter relay 12 - ammeter - instrument switch 19 and starter - heater motor relay 13 - button 14 - switch winding -15 mass - "-" batteries.

Switch 15 is activated and connects the “-” of the batteries to the vehicle ground.

It should be borne in mind that the button 14 must not be kept pressed for more than 2 s, otherwise the electromagnet winding of the switch 15 may overheat.

The normally closed contacts of the relay 13 of the cabin heater electric motors are used to supply current to the solenoid coil of the switch 15. This is done to prevent the possibility of disconnecting the batteries

Simplified EFU connection diagrams (to make it easier to understand how an electric torch device works):

Simplified EFU Wiring Diagrams

Simplified EFU Wiring Diagrams

Possible malfunctions of the EFU and methods of elimination


- Cause of failure


Voltmeter pointer at the bottom of the scale

- Closing the spiral of a thermal relay or electrical wires

If the candles are in good condition, disconnect the wire from the thermal relay that connects it to the power button of the EFU.

The absence of a change in the readings of the arrow indicates the closure of the thermal relay spiral. In this case, replace the thermostat.

If the coil of the thermal switch is intact (determined by touch) and the position of the arrow does not change when the wires are disconnected from the candles, this indicates a short circuit in the electrical wires.

Remove the short.

- Closing the spark plug to ground

Disconnectthe wire from the output of the left candle, eliminating the contact of the tip with the ground, and turn on the EFU again. When the arrow goes beyond the scale, disconnect the wire from the output of the right candle.

The absence of the arrow going beyond the scale indicates the closure of the right candle. Replace failed spark plug.

After the short circuit is eliminated, it is recommended to check the condition of the insulation of the electrical wires, the operability of the thermal relay and the EFU switch-on relay, and if the short circuit occurred when the engine was started, the operability of the shunt relay

Voltmeter reading does not change

- Thermal relay coil burnout

Turn on the EFU and check the voltage at the thermal relay outputs. The absence of voltage at the terminal on the side of the plug connection, while there is voltage at the other terminal, indicates a burned out spiral.

Replace thermostat

- Burnout of candles or lack of contact in the circuit

Turn on the EFU and check for voltage at the terminals of each EFU item, starting with the flare plugs. The presence of voltage at the output of the right candle indicates the burnout of the candles. Replace the spark plug and reconnect

- Burnout of one of the candles

Turn on the EFU for 10-15 seconds, then change the cold plug

No candle torch

- Lack of fuel supply to the spark plug

Loosen the fuel inlet fitting on the spark plug.

Turn on the EFU and, after the indicator lights up (opening the solenoid valve), turn the crankshaft using the starter.

If the fuel does not seep through the loose fitting threaded connection when the valve is open, repair the fuel supply system malfunction

- Fuel not passing through the spark plug

Unscrew the spark plug from the manifold.

Rinse and blow out jet, fuel filter and fuel cavities with compressed air.

Check for torch flame

- Leakage of the fuel supply system

Fix leaks

Checking EFP operation

The operation of the EFU should be checked with good and charged batteries in the following order:

  • - check the serviceability of the signal EFU generator on the instrument panel in the cab (by pressing the control button);
  • —turn on the EFU and determine the time of the moment when the EFU is turned on before the signaling device lights up.

For the first inclusion of the EFU, it should be 50-70 seconds at an air temperature above zero, and 70-110 seconds at a temperature below zero.

When the EFU is turned on again, the signaling device’s ignition time is reduced, therefore, in order to obtain a reliable value, it is necessary to allow the thermostat to cool down to the ambient temperature:

  • - check for the presence of a torch flame in the intake manifolds.

Torch test requires:

  • - unscrew the candles from the collectors, connect fuel pipes and electrical wires to them;
  • - ensure a reliable connection of the candle bodies to the mass and make sure that the terminal is isolated from the mass;
  • —turn on the EFU and, after the signaling device lights up, use the starter to turn the crankshaft.

If there is no flame, then replace the faulty candle.

Determine the performance of relay 4 for turning on the EFU in the following order:

  • - disconnect any wire from the output "K" of the additional starter relay;
  • - press the EFU power button and two or three times for no more than 1 s turn the instrument and starter switch key to position II (rightmost position). With a working relay, characteristic clicks should be heard;
  • - turn off the EFU and connect the wire to the "K" terminal.

Define the operation of the OVG shutdown relay as follows:

  • - press the EFU button and start the engine with a starter. The ammeter needle, when changing the engine speed over the entire range, should show a discharge current of about 30 A. Stop the engine and only then release the EFU button;
  • - Start the engine again and make sure the alternator is charging.

Note. When preparing the car for the first winter operation, additionally check the fuel supply to the EFU candles and the throughput of the candles.

EPS repair

The products of the electric torch device are not subject to repair; if a product failure is found, replace it.

To check the fuel supply to the spark plugs, disconnect the fuel line from the spark plug and bleed the engine supply system with fuel with a manual fuel priming pump.

Then open the electric valve by applying voltage to the valve plug from the plug of the engine compartment lamp wire.

Fuel should emerge from the disconnected fuel line.

Determine the throughput of the candle on domestic stands SDTA-3 (KI-22201) or NC-108-1318 of the company "Mogra1" Czechoslovakia and others, which allow you to smoothly adjust the fuel pressure.

With an overpressure of diesel fuel of 73.6 kPa (0.75 kgf/cm2) and a temperature of 15-25°C, the throughput of the candle should be 5.5-6.5 cm3/min.

Measurement should be done after pre-filling the spark plug with fuel for 20-30 seconds.

Checking EFD operation

In the absence of the indicated stands, assemble the installation according to the diagram in fig. 5.

To determine the amount of current consumed by a candle assemble a circuit (Fig. 6) that allows you to have a DC output voltage of 19 V.

Checking EFD operation

Maintain the voltage with a rheostat 2. At this voltage, the current consumed in a minute after turning on the candle should be 11-11.8 A.

Checking EFD operation

To check the thermal relay parameters assemble the circuit shown in fig. 7.

Install the thermal relay on a horizontal surface with the protective screen up.

Set and maintain the rated current of 22.8 A through the relay with rheostat 2.

Determine the time until the contacts close and keep them in the closed state by the ignition of the control lamp 4. To do this, connect one wire of the control lamp to the thermostat plug, and the second to a DC source (battery).

The time from the moment the current is turned on to the closing of the thermal relay contacts (lighting of the control lamp) at an ambient temperature of 15-25 ° C should be 55-65 seconds, and the hold time I contacts (burning of the control lamp) after switching off - at least 45 seconds.

Check the tightness of the solenoid valve by supplying compressed air at a pressure of 147 kPa (1.5 kgf/cm2) to the valve inlet.

When the valve is immersed in water, no air bubbles should be released


For service "C" (in autumn):

  • — wash the spark plugs and free the EFU fuel lines from summer fuel (after replacing the fuel in the power supply system with winter fuel);
  • - check the operation of the EFU.

EFU spark plug maintenance

When washing the EFU candles, clean the protective sleeve 1 (Fig. 10) and grid 2 from deposits, then rinse them with gasoline.

To release the EFU fuel lines from summer fuel after replacing it with winter fuel in the electric motor power system:

  • - start the engine and let it run at an average crankshaft speed until the rest of the summer fuel from the power system is completely exhausted;
  • - stop the engine and disconnect the fuel lines from the spark plugs;
  • - open the solenoid valve by applying voltage to its plug from the plug of the engine compartment lamp wire. The weight of the vehicle must be included. The opening of the valve is accompanied by a characteristic click;
  • — bleed the engine power system with a manual fuel priming pump until summer fuel is drained from the EFU fuel lines;
  • —connect the fuel lines.