The switch is defective
The switch blocks the flow of fuel to the injectors. When the switch is faulty, the system does not work. If the engine does not start despite the glow plugs being in good condition and the tank is full, there is a suspicion that the switch is faulty. It is checked as follows.
First of all, check: is the wire leading to the switch in good condition?
While the assistant turns the ignition key, listen for a short metallic sound (click) from the switch when the key is turned. If there is no sound, the switch itself is defective or there is a fault in the wiring.
Next, check the wiring. To do this, turn the key in the lock and bring the test lamp to the switch contact.
If the light is on, the wiring is OK.
If the bulb does not light, then the wire leading from the ignition switch is defective. The fuse is not involved.
The illustration shows a disassembled switch; it is taken from a high-pressure fuel pump from Bosch. The switch consists of a housing (1) and a piston (2)
Driving with a faulty switch
If the switch is faulty or there is something wrong with the wiring, you can still continue driving. To do this:
- disconnect the wire from the switch;
- unscrew the switch from the fuel pump;
- remove the valve piston from the switch;
- screw the switch housing back in (tightening torque is 40 Nm);
- the engine is started as usual; to stop the engine, you need to apply the handbrake, engage the gear and, without adding "gas", release the clutch;
- in a car with an automatic transmission, to stop the engine, you need to press the mechanical switch located at the front of the pump.
Note: Leaks near the fuel pump feed control lever can be eliminated by replacing the sealing ring. To do this, remove the pump cover: readjust the fuel pump. This work should be performed by a workshop.
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