1 - hose fitting
2 - adjusting washer
3 - atomizer spring
4 - atomizer body
5 - spray needle
To a certain extent, injectors are the last stage of the engine injection system. Their task is to inject high-pressure and finely atomized fuel into the vortex chamber. Initially, when the fuel pressure exceeds the set injection pressure, the atomizer needle rises from its seat and can enter the swirl chamber. The injection pressure of the atomizer is 130-138 bar for a 47 kW suction diesel, 150-158 bar for a turbodiesel.
However, if the high spring force obstructs the atomizer needle, then the ignition pressure returns back to the fuel system. If the needle remains in «hung» condition, the corresponding nozzle draws attention with too loud knocking.
Cooling and lubrication of the atomizer needle is carried out by fuel, since never all the incoming fuel can 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 work. Irregular and unprofitable fuel supply, poor mixing with air, uncontrolled ignition (in a gasoline engine, you can talk about detonation) will be a consequence of this. The driver should notice poor engine performance and/or harsh engine noise - so-called «nails».
«Nails»
The harsh combustion noise typical of a diesel engine, which sounds like hammering in nails, has already been noticeably reduced on our diesel engine. It is only during the cold engine phase that this noise cannot be completely eliminated. When a warm engine emits «nail-shaped» sounds, the reason lies mainly in the slowing down of the ignition process, therefore, the time between the start of injection and the self-ignition of the mixture is too long.
There may be the following reasons:
- Clamped spray needles.
- Inappropriate diesel fuel, such as summer diesel fuel, which is used at low temperatures and has a tendency to wax (release of paraffin).
- Too much load at low speed.
- Compression pressure too low.
Among the circumstances contributing to the elimination of this may be «internal cleaning», which uses fuel with a fuel system cleaning additive, which is sold in specialty stores. A quick trip on the Autobahn often helps too.
Are the injectors faulty?
Some injector defects can be found with the engine running, when the nuts are loosened and re-tightened on all injectors in sequence, covering the fuel lines on the injectors. If, when the fuel line at one of the injectors is loosened, the engine speed remains unchanged, then this is the point.
The following effects may indicate faulty injectors:
- Faulty spark plugs glow constantly or for a short time.
- Thick black smoke from the exhaust.
- High fuel consumption.
- Engine overheating.
- Strong knocks.
- Power drop.
- Uneven engine operation.
Self-repair of the injection system
Below are some of the types of work that it still makes sense to carry out on your own initiative. Naturally, more can be done. We believe that the leakage of the current injection pump, a defect that is often found in the control lever (lever arm «gas»), it is better to fix in the service «Volkswagen» or «BOSCH».
Removing the nozzle
Buy a new heat-insulated gasket for the removed nozzle.
Remove the high pressure fuel line so as not to change its bent shape.
Remove return pipe.
Unscrew the nozzle using a ring wrench or a 27 mm socket.
Pull out the thermal insulation using a plastic or wire hook.
Install a new one to install (!) heat insulating pad.
Tighten injector to 70 Nm, high pressure pipe to 25 Nm.
Top part (8.22 mm) screwed into the bottom (1.27 mm). The following items are inside
2 - atomizer body
3 - spray needle
4 - needle holder assembly
5 - pressure bolt
6 - atomizer spring
7 - adjusting washer
An important point during disassembly: the nozzle should not lie open, but is immediately installed on the engine and it should work for some time. Nozzle parts are subject to rust. Tightening torque for top/bottom connection: 70 Nm.
Note: Workshops have a tester with which the injection pressure can be checked. There are also adjusting washers necessary for adjustment.
Faulty stop device?
To turn off the engine, the stop device blocks the flow of fuel to the injectors. If it is defective or clogged, it should no longer be used. A stop device is suspected when the engine, despite a good pre-glow system and a sufficiently full tank, does not have any flashes. Here is the procedure for checking the device:
Nozzle disassembly
Only in exceptional cases (pollution) it is worth disassembling the injector. For self-repair, however, it makes sense to completely replace the nozzle; an accurate injector check or injection pressure adjustment cannot be carried out in amateur conditions.
First of all, check if the wire to the stop device is good.
While the assistant turns the ignition key, listen to the device to see if it emits when turned on "ignition" clear click.
If this does not happen, then the voltage supply or the engine stop device itself is faulty.
Check the current supply: switch on the ignition and connect a test lamp to the contact of the stop device.
If it is on, then the ignition cut-off wire to the device is faulty. The fuse is nothing.
Driving with a faulty stop device
If the stop device is faulty or there is a problem with the power supply, you can still drive. For this:
- Remove the cable from the engine stop device.
- Unscrew the stop device from the injection pump.
- Remove the piston with valve from the stop device.
- Screw the housing back with a torque of 40 Nm.
The engine now starts as usual, but to stop it must be turned off with the gear engaged (slow down).
On vehicles with automatic transmission, the mechanical stop device installed on the front side of the injection pump must be actuated to stop it.
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