Preheater PZhD-30 of Kamaz car

Electrical devices of the preheater are designed to perform the following functions: induction coil 2 (figure) with a transistor switch generates a high voltage

and creates a spark in spark plug 3:

  • button 6 turns on the fuel heater in the power circuit; heater 5 heats the fuel entering the nozzle;
  • Solenoid fuel valve 4 turns the fuel supply to the injector on and off;
  • electric motor 1 drives the pump unit.

The electric motor 1 of the pumping unit, which consumes high current, is powered through the contactor 8. This allows the use of a low-current switch 7, which has relatively small overall dimensions.

The heater is started in the following sequence: the batteries are connected to the network by pressing the remote ground switch-off button, then the switch handle 7 is moved to position III and the button 6 is pressed.

This turns on the electric motor 1 (purge mode) and energizes the electric fuel heater 5.

Battery power is supplied to the contactor through the circuit: "+" batteries - AM and VK terminals of switch 7 - contactor winding 8 -  "-" batteries.

In this case, the contactor 8 is activated, providing the passage of current through the windings of the electric motor 1, along the circuit:

  • "+" batteries
  • — terminal AM of switch 7
  • — closed contacts of contactor 8
  • — motor windings 1
  • — "—" batteries.

When the electric motor is switched on, the heater boiler is purged with air.

Electric heater 5 is powered by the circuit: "+" batteries - AM terminal of the switch 7 - closed contacts of the contactor 8 - closed contacts of the button 6 - heater 5 - "-" of the batteries.

Button 6 is kept pressed depending on the ambient temperature: for 30 s at -30 °C, 60 s at -40 °C and up to 90 s at -50 °C.

The switch handle is then moved to position I (start mode). This will turn on the electric motor 1, the electromagnetic fuel valve 4, the transistor switch 2 and the spark plug 3.

Valve 4 power supply circuit: "+" batteries - terminals AM and short circuit of switch 7 - valve winding 4 - "-" batteries.

Valve 4 opens and passes fuel to the injector.

Power circuit of transistor switch 2:

  • "+" batteries
  • — terminals AM and CT of switch 7
  • - Switch 2
  • — "—" batteries.

The commutator generates a high voltage current, which is fed to candle 3. Sparks form in the candle

The fuel pump pumps fuel through the open valve 4 into the injector.

The atomized fuel mixes with the air entering the burner through the swirler and ignites from the candle.

A hum is heard when fuel burns.

The switch handle 7 is held in position I for no more than 30 s.

As soon as a hum appears in the boiler, it is released and it will automatically take position II - the main mode of operation of the heater.

This will turn on the electric motor / and valve 4, the electrical circuits of which were discussed earlier.

The ignition of the combustible mixture in position II of the switch handle 7 occurs from the flame.

Kamaz heater wiring diagram

Heater wiring diagram

Kamaz preheater


Scheme of operation of preheater Kamaz

Scheme of operation of preheateri

Heater specifications

Type: PZhD-30

Heat output, kJ/h (kcal/h): 108857(26000)

Fuel: used for the engine

Fuel consumption, kg/h: 4.5

Ignition of fuel: with an electric spark plug from a transistor switch with an ignition coil TK107

Candle operation time, s: 30

Fuel pre-heater: 200W pin electric spark plug

High-voltage candle: CH-423, electric spark

High voltage switch: TK 107, transistorized

Solenoid valve: MKT-4

Heater motor: ME 252, power 180 W

Motor circuit contactor: KT 127

Fuel heater relay: 11.3704.000

Operating mode switch: VK354

Fuse: one for 30 A, PRZ thermal bimetallic. Protects the power supply circuits of the electrical equipment of the preheater

Seasonal maintenance of pre-heater (service C) in autumn:

Fix the pump unit, heat exchanger, pipes, outlet pipe of the preheater.

Seasonal preheater maintenance (C service) in autumn

  • The tightening torque of the pump unit mounting bolts is 44-53 Nm (4.5-5.4 kgf-m);
  • The tightening torque of the heat exchanger mounting bolts is 44-53 Nm (4.5-5.4 kgf-m);
  • The tightening torque of the M10 bolts of the pipe is 44-53 Nm (4.5-5.4 kgf-m); exhaust pipe bolts - 15-25 Nm (1.5-2.5 kgf-m).

Seasonal preheater maintenance (C service) in autumn

Rinse the channels and filters of the solenoid valve, heater fuel tank valve, preheater injector, clean the preheater plug electrodes, combustion chamber and heat exchanger flue, check the operation of the preheater, troubleshoot (in autumn).

Before flushing, disassemble the heat exchanger, remove carbon deposits.

Wash the filters of the solenoid valve in kerosene, the nozzle in acetone, and the rest of the parts in diesel fuel.

Normal operation of the preheater is determined by the uniform hum of combustion in the heat exchanger and the exit of exhaust gases without smoke and open flame.

If necessary, adjust the fuel flow with the fuel pump pressure reducing valve by doing the following:

  • - unscrew the cap nut on the fuel pump; loosen the adjusting screw locknut;
  • - by turning the adjusting screw to the right (fuel supply increases) or to the left (fuel supply decreases), adjust the heater operation mode.

After adjusting, lock the adjusting screw with a lock nut and screw on the cap nut.

To ensure normal operation of the heater, adjust the fuel supply when the ambient temperature is below zero.

After washing the car or crossing the ford in the cold season, remove the water that has entered the air path of the fan by turning on the pump unit for 3-4 minutes (set the switch to position III, after disconnecting the wire going to the electric fuel heater)

Possible malfunctions of the preheater and methods of elimination


- Cause of malfunction


Heater wont start

- There is no voltage in the power supply circuit of the heater, the polarity of the battery connection is reversed

Check fuses, wiring, polarity

- Faulty collector or brushes of the fan motor

Replace motor or brushes

- Open circuit of the electric motor of the circulation pump

Check the operation of the pump by connecting it directly to the battery

No ignition, control unit turns off automatically

- Lack of fuel

Fill fuel

- Fuel "frozen" in pipelines (at low temperature)

Pour in the recommended fuel.

Blow out the pipelines, clean the filter

- The fuel pump does not supply fuel

Check drive, replace pump

- Solenoid valve does not open

Check the electrical connections of the valve, replace the solenoid valve. Check thermal fuse (for press his button)

- Nozzle clogged

Replace nozzle

- No ignition voltage

Check wiring and plug connections.

Replace the control unit.

Replace high voltage power supply

- Leakage of pipelines (the pump sucks in air)

Tighten fuel line connections

- Incorrectly installed ignition electrodes

Adjust gaps between electrodes and nozzle

- Too much combustion air

Adjust the air supply with the air intake damper

The heater does not provide good combustion

- Excess fuel, nozzle clogging

Replace nozzle

Soot forms on the exhaust

- Lack of combustion air (the heater smokes "thickly").

Clean the suction air inlet.

Adjust the position of the air intake damper

- Poor fuel atomization

Replace nozzle

Fix undervoltage, replace brushes, replace motor

- The exhaust pipe for exhaust gases is bent or displaced, clogged with soot, dirt

Fix or clean the outlet pipe, clean the heat exchanger (flame tube and heat exchanger inner tube)

Blue smoke coming out

- Lack of fuel. Nozzle or filter clogged

Clean or replace the nozzle. Clean the filter.

- Too much combustion air.

Adjust the position of the air intake damper

Heater cut off by thermal fuse

- Lack of coolant in the cooling system

Fill the circulation system with coolant and eliminate air pockets

- Faulty remote thermostat

Replace thermostat

- No or little coolant circulation

Check whether the circulation pump is connected and working properly

The heat output of the heater is insufficient

- Soot in the combustion chamber and heat exchanger

Clean combustion chamber and heat exchanger

- Scale has formed in the heat exchanger


The heater makes a lot of noise during operation

- The fan impeller touches the housing

Adjust the gap between the housing and the impeller and fix it

- Faulty fuel pump

Replace pump