Injector control

In the last five years, automotive manufacturers have mostly...

abandoned traditional diesel engines. More modern mechanics, equipped
very sophisticated injection technologies replace them. As a result, in vintage
equal, some models are found second-hand alongside their counterparts.
classic diesel engines and sold at slightly higher prices. The temptation to
launching into new concepts is great. But here we are, the beginnings of a career of
these engines have been marred by worrying and sometimes costly incidents.
flaws that do not encourage the purchase of the first generations. The most
recently show better morale. But it's better to make sure before doing the
check.
Reminder of techniques
1The traditional
Indirect injection
It is the oldest technology. Diesel is injected into a pre-chamber.
located in the cylinder head, before the cylinder. Despite good performance, it is the
less sober and the most polluting. But its reliability is not to be questioned. In
testify the numerous models that display more than 250,000 km, without having
met with major troubles.
Direct injection
It first appeared in the late 1980s, on the Fiat Croma.
diesel is injected directly into the cylinder. More fuel-efficient than
the indirect injection, it is also more efficient. Only complaint: it is
noisy when cold.
The moderns
Common rail injection
Alfa Romeo inaugurated it with the 156 JTD at the end of 1997. It is a direct injection system.
high pressure (1,600 bars), more efficient and more economical than Diesel injection
traditional. But it has sometimes faced youth reliability issues.
The pump injectors
The Volkswagen group (Audi, Seat, Skoda, VW) opted for a system with injectors-
pumps (one per cylinder), offering even higher pressures (2,000 bars).
From excellent performance and very low consumption. Good reliability
together
How to recognize them
Traditional diesel
Modern diesel
Citroën and Peugeot TD turbo Diesel
indirect injection
HDi turbo diesel injection
high pressure Common
rail
Fiat, Alfa Romeo and TD
turbo Diesel at
JTD turbo Diesel injection
high pressure Common
rail
Lancia
indirect injection
Ford
TD turbo Diesel to
indirect injection
TDCi turbo Diesel with injection
high pressure Common
rail
TDdi turbo Diesel
direct injection
average pressure
Mercedes
Opel
TD turbo Diesel in
indirect injection
CDI turbo diesel injection
high pressure Common
rail
TD turbo Diesel
indirect injection
DTI turbo Diesel with injection
(2001 high pressure Common
rail
DI Diesel injection
direct without turbo
DTI turbo Diesel
(-> direct injection
2001) medium pressure
Renault
Toyota
dT turbo Diesel to
indirect injection
turbo injection Diesel dCi
high pressure Common
rail
dTi turbo Diesel
direct injection
average pressure
TD turbo Diesel to
indirect injection
D4-D turbo Diesel injection
high pressure Common
rail
Volkswagen, Audi, SDI Diesel injection
Seat and Skoda direct without turbo
TDI turbo Diesel injection
2001 high pressure injectors
pumps
Diesel injector control
(source Peugeot)
During the injector check, care must be taken to ensure that the fuel spray does not arrive
not on the hands,
because the fuel would penetrate the skin due to the high pressure and could
cause serious injuries.
Characteristics to note:
Brand;
Injectors;
Injector nozzle holder;
Setting pressure.
IMPORTANT
The installation of an injector or injector holder that does not match the
type of pump for which they are intended causes a consumption
abnormal, smoke in the exhaust and leads to rapid destruction of
the injector and even that of the engine
INJECTION CONTROL
Use the calibration pump equipped with a connecting tube featuring an Ermeto fitting.
Precaution for use:
Before disconnecting a controlled injector holder, turn off the valve (2) to
isolate the manometer.
When the injector connector is unplugged, gradually open the valve.
(2) for the manometer needle to descend slowly to its stop.
Any sudden drop in pressure could distort the manometer.
Have the accuracy of the manometer periodically checked using a holder
injector calibrated at 120 bars.
REMOVAL OF INJECTOR HOLDERS
Clean the top of the cylinder head.
Drop the injection pipes.
Unplug the return line.
Submit:
the brides,
the injector holders,
copper joints,
the wavy discs (flame barriers).
NOTE. Never disassemble an injector holder before checking its
operation on the control device.
DESCRIPTION OF THE INJECTOR HOLDER
AND THE INJECTOR
Injector holder
2 - Cap nut
3 - Adjustment washers
4 - Adjustment spring
5 - Push rod
Injector needle
Nipple
8 - Injector nozzle
9 - Nozzle Nut
10 - Arrival channel
11 - Return Canal
OPENING PRESSURE CONTROL
Pressure gauge valve closed:
Actuate the pump lever several times to purge the injector to be checked.
Open manometer valve:
Gradually push the pump lever and increase the pressure
until the injector opens.
Adjust the setting pressure if necessary by inserting a washer.
adjustment between the spring (4) and the cap nut (2).
Greater thickness = increases injection pressure.
Thinner thickness = reduces injection pressure
An increase in preload of 0.05 mm raises the injection pressure by 5.
bars around.
Remark
When refurbishing ground injectors, the pressure must be adjusted.
injection to the value for new injectors.
CONTROL OF THE INJECTOR OPERATION
Jet shape:
Shutoff valve (2) of the pressure gauge.
This control cannot be effectively carried out at the calibration pump.
However, for a pumping rate of 1 stroke per second, the injector will be
considered bad if there is never any repetition.
Even an irregular jet repetition cannot be a criterion to dismiss the injector.
Spraying:
Only judge the quality of the spraying when the injector 'repeats' but do not
consider an injector defective if it shows a non-homogeneous or poor spray
distributed around the nipples (slightly deviated from the axis of the injector).
Operational noise:
The nipple injector with a choke is characterized by a noise of
function called "snoring".
snoring verification is only possible at a speed of 1 to 2
lever movements per second.
As you accelerate, the humming disappears.
This rumbling is a good sign of the injector's functioning.
WATERPROOFING
Raise the pressure on the manometer to 10 bars below the pressure.
opening for 10 seconds.
No drop should fall from the injector's nose (there should be no moisture)
not be a disqualifying criterion.
DISASSEMBLY OF THE INJECTOR HOLDER AND INJECTOR
Tighten the injector holder in lead jaws.
Disassemble in the order of the diagram: 2-3-4-5-6.
Immediately immerse the disassembled parts in clean diesel.
CLEANING OF THE INJECTOR
In any case, the refurbishment of an injector should be limited to some
cleaning operations.
The use of an abrasive product for grinding as well as for the finishing of
Seats of the injector body or the needle should be avoided.
Decarbonize the injector nozzle with a wooden spatula.
Clean each injector individually to avoid mismatching
needles and the nozzles.
The needle must slide freely and descend into the nozzle by its own.
weight
REASSEMBLY OF THE INJECTOR AND INJECTOR HOLDER
Wash the needle and the nozzle of the new injectors in diesel.
Always soak the parts in clean diesel before assembly.
Check the sliding of the needle.
Place the needle in the injector nozzle on the injector holder and screw it on.
the fixing nut
Tightening torque ... m.daN
Insert the push rod, the spring, the washer or screw on the nut of
setting.
Tighten the cap nut (1) with its copper washer to ... m.daN.
Check the calibration
Injector Holder Rest
Replace the copper seal and the waved washer.
Coat the injector holder with the bracket. without tightening.
Manually screw the injection pipe connections onto the pump, then onto the
injector holder to center the tips.
Tighten moderately, max ... m.daN, the connectors on the pump then on the door-
injector.
Tighten the two nuts of the flange: ... mdaN.
Connect the return pipe.
NOTE
In case of a leak from a fitting, do not tighten further. Unscrew the fitting.
and screw it back in.
Diagnostic
CASES
DEFAULTS
CONSTITUTES
REMEDIES
PROPOSES
Cleaning in the
"trichlore" with a
wooden spatula
Deposit of scale at the level of
the orifice
Deflected jet
and
jet parasites
Stripes on the nozzle seat
Needle in poor condition
Replace the injector
Foreign body stuck between the seat
of the buzzard and the needle
Clean
Missing
sealing
Deformed buzzard seat
traces of seizure
Replace the injector
excessive tightening of the
bitch on her seat
Torque couple of the
1.5 mdaN (1)
near the cone
injector bride too
tight
copper joint not
Replace the seal at
each intervention
to the part
median
replaced
Needle
with the flu
excessive tightening of the torque
bride
1.5 mdaN (1)
or in progress
of jamming
excessive tightening of
Torque couple of
the seat nut on the seat nut 6 to 7
to the part
superior
injector sleeve
copper joint no
replaced
mdaN (specific tool)
Replace the seal at
each intervention (1)
Drain and rinse the
power supply circuit
(in these 4 cases,
Water in the diesel fuel
replace the injector