Nozzles (VW Golf 3)

To a certain extent, the injectors are the last stage of the engine injection system. Their task is to inject fuel under high pressure and finely atomized into the swirl chamber. Initially, when the fuel pressure exceeds the set injection pressure, the nozzle needle rises from its seat and can enter the swirl chamber. The injection pressure of the nozzle is 130-138 bar for a 47 kW suction diesel engine, and 150-158 bar for a turbodiesel.

However, if the high spring force prevents the spray needle, the ignition pressure returns back to the fuel system. In the case where the needle remains in a "hung" state, the corresponding nozzle attracts attention with an excessively loud knock.

Cooling and lubrication of the spray needle is provided by fuel, since all the incoming fuel can never be injected completely. Then it flows back into the tank through the return line.





The set time between the start of injection and ignition reaches 0.002 sec. Here, even the slightest inaccuracy is a reason for incorrect operation. Irregular and unprofitable fuel supply, poor mixing with air, uncontrolled ignition (in a gasoline engine we can talk about detonation) will be the consequence of this. The driver should notice poor engine performance and/or a harsh engine noise - the so-called "nails".

"Nails"

The typical diesel hard combustion noise, which sounds like hammering nails, is already noticeably reduced in our diesel engine. Only during the cold engine phase can this noise not be eliminated completely. When a warm engine produces "nail-like" sounds, the cause lies mainly in the slowing down of the ignition process, i.e. the time between the start of injection and the spontaneous ignition of the mixture is too long.

There may be the following reasons:

• Pinched spray needles.
• Inappropriate diesel fuel, such as summer diesel fuel, which is used at low temperatures and has a tendency to wax (paraffin separation).
• Too much load at low RPM.
• Compression pressure too low.

Among the circumstances that can help eliminate this, there may be an "internal cleaning" that uses fuel with a fuel system cleaning additive, which is sold in special stores. A quick drive on the autobahn often helps as well.

Are the injectors faulty?

Some injector defects can be found on a running engine, when the nuts that cover the fuel lines on the injectors are loosened and tightened one after another on all the injectors. If the engine speed remains unchanged when the fuel line on one of the injectors is loosened, then that is the problem.

The following effects may indicate faulty injectors:

• Defective spark plugs glow continuously or for a short time.
• Thick black smoke from the exhaust pipe.
• High fuel consumption.
• Engine overheating.
• Loud knocking.
• Power loss.
• Uneven engine operation.

Self-repair of the injection system

Below are some types of work that still make sense to do on your own initiative. Naturally, more can be done. We believe that the leakage of the current fuel injection pump, a defect that often occurs in the control lever (the "gas" lever), is best eliminated at the Volkswagen or BOSCH service center.

Removal the injector

Buy a new heat-insulated gasket for the injector being removed.

Remove the high pressure fuel line to avoid changing its bent shape.

Remove the return pipe.

Unscrew the injector using a 27 mm open-end wrench or socket.

Remove the heat-insulating pad using a plastic or wire hook.

The text is copied from this portal [VWmanual.ru]

For installation, install a new (!) heat-insulating gasket.

Tighten the injector to 70 Nm, the high pressure pipe to 25 Nm.



Important point when disassembling: the injector should not lie open, but immediately be installed on the engine and it should work for some time. The injector parts are subject to rust. Tightening torque of the upper/lower part of the injector: 70 Nm.

Note: The workshops have a test device with which the injection pressure can be checked. The adjusting washers necessary for adjustment are also available there.

Is the stopping device faulty?

To turn off the engine, the stop device closes the fuel supply to the injectors. If it is faulty or clogged, it should no longer be used. The stop device is suspected when no flashes occur in the engine, despite a working pre-heating system and a sufficiently full tank. Here is the procedure for checking the device:

Disassembling the injector

Only in exceptional cases (pollution) it is worth disassembling the injector. For independent repair, however, it makes sense to completely replace the injector; accurate testing of the injector or adjustment of the injection pressure cannot be carried out in amateur conditions.

First of all, check if the wire to the stopping device is in good condition.

While the assistant turns the ignition key, listen to the device to see if it makes a distinct click when the ignition is turned on.

If this does not happen, the voltage supply or the engine stop device itself is faulty.

Check the power supply: turn on the ignition and connect the test lamp to the contact of the stop device.

If it lights up, then the ignition cut-off wire to the device is faulty. The fuse has nothing to do with it.

Driving with a faulty stopping device

If the stop device is faulty or there are problems with the voltage supply, you can still continue driving. To do this:

• Remove the cable from the engine stop device.
• Remove the stop device from the high-pressure fuel pump.
• Remove the piston with the valve from the stop device.
• Tighten the housing back to a torque of 40 Nm.

The engine now starts as usual, but to stop it you need to turn it off with the gear engaged (slow down).

In vehicles with automatic transmission, to stop the engine, you must operate the mechanical stop device installed only on the front side of the injection pump.