FUEL INJECTION SYSTEM

DESCRIPTION AND OPERATION

The function of the fuel 'PUMP INJECTOR'
is to:
(a) raise the pressure of the fuel
sufficiently for it to open the integral
injector nozzle valve and spray a
predetermined amount of atomised fuel
into the combustion chamber,
(b) deliver an equal amount of fuel to each
cylinder,
(c) inject the fuel at precisely the correct
moment for the most efficient
combustion, and
(d) vary the amount of fuel injected in Key
accordance with the requirement of the (Fig. 1P)
engine at all conditions of load and 1 Fuel supply
speed. 2 Rocker box
The pump injectors are individual units 3 Cylinder head
mounted in the centre of each cylinder head 4 Fuel return
and secured in position by a forked clamp.
Each unit performs the function of pump and Adjustment of the injector pressure setting is
injector. The pump control plunger helix is varied by fitting shims of the correct
operated from the engine governor, mounted thickness at the top of the injector spring, ail
at the front of the engine, via transverse and enclosed within the lower housing. Shims
longitudinal linkages. are supplied in various thickness from 0.011"
Each pump injector is cam and rocker lever to 0.080" (0.28 to 2.03 mm).
operated giving a constant stroke, with The injector is fitted with a nozzle with eight
facility for setting the point at which the 0.30 mm (0.0118") diameter holes.
spring plunger assembly starts the pumping Fuel from the rail enters the rocker box via a
stroke (which determines the point of drilling which lines up with another drilling in
injection), using the timing pin fitted to the the cylinder head and into the fuel pump
element housing. chamber. From the pump chamber, fuel
NOTE: The plungers and element housings enters the bore of the pump via a drilling in
are manufactured to extremely fine limits the unit injector body.
and the working surfaces are tapped The fuel flow to each cylinder is regulated by
together. For this reason plungers and the control arm and the helix on the pump
element housings are not interchangeable. plunger. The excess fuel is returned out of
This also applies to injector nozzles and the body back into the pump chamber via a
needles. hole in the body. Fuel is then returned to the
The element housing is lubricated internally rail via a drilling in the cylinder head (see Fig.
with fuel. i p ).
The pump injector enclosed within the
cylinder head is arranged for a through flow
of fuel, thus keeping the operating
temperatures down and allowing for a more
consistent supply of fuel over a wide range of
engine loads and speeds.

4012/16 Diesel, February 1997 Section P1

From the library of Barrington Diesel Club
FUEL INJECTION SYSTEM

WARNING BATTERIES OR
A
ANY OTHER
MEANS OF STARTING THE ENGINE
WHEN WORKING ON THE FUEL
INJECTION SYSTEM.

REMOVING THE INJECTOR

Remove the rocker box cover by taking out
the 4 slot head screws Fig. 2P. Rotate the
engine, watching the injector rocker,
stopping the engine rotating when the
injector rocker is on minimum lift i.e. injector
at its uppermost travel.
Remove the nut and capscrew from the
rocker shaft then lift off the rocker assembly
taking care not to drop the hardened cup
between the injector rocker arm and the
injector Fig. 3P. Take out all three push rods,
plus the inlet and exhaust rocker bridges,
marking them for reassembly in the same
order.
Loosen the fuel feed and return union nuts
thereby allowing fuel to drain from the fuel
rail Fig. 4P.
Disconnect the governor mechanism from
the control arm Fig. 5P. Take care not to
drop the capscrew or collar between the ball
joint and control arm.

Key
(Fig. 3P)
1 Capscrew
2 Hardened cup

Section P2 4012/16 Diesel, February 1997

From the library of Barrington Diesel Club
 FUEL INJECTION SYSTEM

Finally, remove the capscrew from the

injector clamp. Then, using ciawfoot tool Part
No. T6253/145, under the clamp, gently
lever the injector out. Fig. 6P.
NOTE: The injector should not be pulled
upwards by the spring mechanism, as this
will only lift the plunger from the barrel.
When the injector is out of the cylinder head
discard the copper washer. Fig. 7P. Remove
copper washer from bottom of injector tube, if
it does not come out with injector.
NOTE: On removal of injector, fuel left in the
gallery of the cylinder head will unavoidably
run down into the cylinder bore. To avoid
serious damage caused by ‘hydraulic-ing1it
is essential to remove as much of this
unwanted fuel as possible. Rotate the
engine to top dead centre on the cylinder in
question and using a length of plastic tube
siphon off the excess fuel which has
accumulated in the piston bowl. Later, when
the engine is being prepared for start-up,
rotate the engine on its starter for 10
seconds with the governor lever in the stop
position as an added precaution. Fig. 6P

WARNING do n o t ro ta te
AON STARTER
WITHOUT THE ROCKER ASSEMBLY
FITTED AS DAMAGE TO THE CAM
AND PUSH ROD MAY OCCUR.

STRIPPING AND CHECKING A PUMP

INJECTOR
IMPORTANT Pump injector dismantling,
servicing and testing should only be carried
out where suitable test equipment is
available. Pump injector dismantling and
assembly must be carried out under dust
free conditions on a bench used specifically
for this purpose. The bench should be (Fig. 7P)
covered with zinc or linoleum and be 1 Copper sealing washer
provided with a suitable vice equipped with
copper or zinc grips.

NOTE: FOR THE PURPOSE OF THIS

TEXT, WHETHER THE PLUNGER
ASSEMBLY IS SEPARATED FROM THE
ELEMENT HOUSING AND NOZZLE OR
NOT, THE UNIT IS REFERRED TO AS THE
INJECTOR.

4012/16 Diesel, February 1997 Section P3

From the library of Barrington Diesel Club
FUEL INJECTION SYSTEM

NOTE: it is advisable to work on one injector

at a time so as to eliminate the possibility of
the plungers being assembled into the wrong
element housing.

TO DISMANTLE
NOTE: Before dismantling pump injectors
which are in a very dirty condition seal off the
fuel spill ports and wash in clean fuel.
Brush the nozzle externally with a brass wire
brush to remove all the carbon deposits.
Remove the plunger spring assembly from
the injector using a small screwdriver to prise
up the spring plate locating collar over the
spring dowel and withdraw the plunger
spring assembly from the element housing
Fig. 8P.

NOTE: THE PLUNGER SPRING

ASSEMBLY AND ELEMENT HOUSING ARE
A MATCHED PAIR AND COMPONENTS
CANNOT BE INTERCHANGED. THE
PLUNGER SPRING ASSEMBLY AND
ELEMENT HOUSING ARE NON-
SERVICEABLE ITEMS. IF EXCESSIVELY
WORN OR DAMAGED, SERVICE
EXCHANGE UNITS ARE AVAILABLE i.e.
VISUALLY INSPECT FOR SCORES,
SCRATCHES, RUST, CHIPS, BROKEN
SPRINGS (INNER AND OUTER).

Place in a bath of CLEAN fuel or calibration

fluid.
Remove the timing pin Fig. 9P.
With the injector clamp Part No. T6253/146
only held in a strong vice, slot the injector
into the clamp (Fig, 10P). Using a suitable
torque wrench and a long 27 mm socket,
unscrew the nozzle nut (8) (Fig. 13P) from
the nozzle (7).

Key
(Fig. 10P)
1 Fuel feed adaptor
2 Injector clamp

Fig. 10P

Section P4 40.12/16 Diesel, February 1997

From the library of Barrington Diesel Club
 FUEL INJECTION SYSTEM

NOTE:
(1) If the injectors have been in service for
some time carbon deposits around the
nozzle and nut may make these
components stick together. It is
therefore advisable to soak the unit in
fuel or calibration fluid to soften the
carbon and avoid possible damage to
the dowels in the transfer block as the
nozzle nut is unscrewed. See Fig. 13P.
(2) If time will not permit soaking the unit,
spray the nozzle nut with 'Plus Gas' or
similar releasing fluid to break down the NOTE: The nozzle body and needle valve
carbon more quickly. DO NOT allow are matched pairs and components cannot
releasing fluid to come into contact with be interchanged. For this reason it is
'O' rings as this may cause rapid recommended that only one nozzle
deterioration. assembly is dealt with at a time.
It will now be possible to lift off the Wash and clean all parts of the element
nozzle and needle (6 and 7), transfer housing assembly with clean fuel paying
block (location adaptor) (5), and thrust particular attention to the nozzle clamping
cap (spring locator) (3) and place in a shoulder. Remove any carbon deposit with a
bath of clean fuel oil or calibration fluid. scraper. Care must be taken not to scratch
Release the injector clamp from the the shoulder.
vice and suspending the remaining part Examine the mating faces of the nozzle
of the assembly over the bath, invert body, element housing and transfer block.
the body to allow the spring (2) and These must be perfectly clean, flat and
shims (1) to be removed and placed in smooth. If any signs of staining or fretting are
the bath with the other parts. Check apparent, the faces must be lightly lapped on
that all shims (1) are removed from the a lapping plate, or if the performance of the
element housing. injector is suspect, the injector should be
tested as described in Sections P9 to P11.
TO CLEAN AND CHECK
The special tool kit (Part No. T6253/202 Fig.
11P) designed to enable quick and safe
servicing of the nozzle assembly MUST
always be used. On no account should tools
other than those described here be used or
serious damage to the nozzle body and
needle valve may result.
Abrasives and metal polish must not be
used on the nozzle body and needle valve.
Before commencing cleaning operations it is
essential to see that the bench is perfectly
clean and that ample supplies of clean fuel
are available.

4012/16 Diesel, February 1997 Section P5

From the library of Barrington Diesel Club
FUEL INJECTION SYSTEM

Allow the needle valve and nozzle body to

soak in clean fuel oil for a short period. Key
Withdraw the needle from the nozzle body (Fig. 12P)
and examine the guide surface. This should 1 Plunger spring assembly
be bright and free from high spots, scratches 2 Spring dowel
and dull areas. Lightly brush the valve 3 Spring plate locating collar
seating with a brass wire brush until bright 4 Element housing
metal is visible over the whole area. 5 Timing pin
If the needle valve is discoloured or high
spots, scratching or dull areas are visible,
the complete pump injector should be
returned to an approved agent for
examination and reconditioning.
The needle lift in the nozzle body, measured
with needle gauge (Part No. T6253/203),
should be from 0.4 mm to 0.6 mm for new
assemblies. If the lift is greater than 0.75 mm
a new nozzle assembly should be fitted.
Examine the nozzle body joint face. This
should be perfectly clean, flat and smooth.
Examine the needle valve bore in the nozzle
body. This should be bright and free from
high spots, scratches and dull areas. Check
the needle valve slides smoothly in the bore.

Section P6 4012/16 Diesel, February 1997

From the library of Barrington Diesel Club
 FUEL INJECTION SYSTEM

Clean out the fuel passages in the nozzle

body with brass wire of suitable diameter.
Insert the fuel chamber scraper (4) (Fig.
11P) into the nozzle body until the nose
locates in the fuel gallery. Press against the
side of the gallery and rotate to clear any
carbon or other deposits,
Insert the seat scraper (2) (Fig. 11P) and
clean all carbon from the valve seat by
rotating and pressing the tool into the seating.
Prick out the holes in the end of the nozzle
body with a short piece of wire 0.3 mm
(0.0118") diameter, holding it by means of
wire holder (3) (Fig. 11P). Extreme care must
be taken to avoid the danger of the wire
breaking in the hole as such particles are
almost impossible to remove. If difficulty is
experienced cleaning out the holes due to the
hardness of the carbon, it is recommended
that the complete pump injector is returned to
an approved agent for attention.
When using the wire holder, the cleaning wire
should be fitted to the tool chuck so that it only
protrudes for about 1.5 mm to 2 mm (V to
W )* thus giving maximum resistance to
bending. Insert the wire into the spray hole
pushing and rotating gently until the hole is
cleared.

WARNING
A WHEN TESTING
INJECTORS,
CARE MUST BE TAKEN TO PREVENT
SKIN CONTACT WITH THE SPRAY,
SINCE THE WORKING PRESSURE
WILL CAUSE THE FLUID TO
PENETRATE THE SKIN,
NECESSITATING IMMEDIATE
HOSPITAL TREATMENT. THE SPRAY
IS ALSO HIGHLY FLAMMABLE.

NOZZLE MULTICLEAN EQUIPMENT (Fig, 13P)

Thoroughly wash away all carbon from the 1 Shims
interior of the nozzle body using nozzle 2 Spring
'Multiclean1 equipment (Fig. 14P) Part No. 3 Spring locator
T6253/204 then blow clean. Wash the body 4
backwards through the spray holes with 5 Location adaptor
clean fuel oil under pressure from the test 6 Needle
pump. Examine the seat closely under a 7 Nozzle body
strong light to ensure that all traces of foreign 8 Nozzle nut
matter have been removed.

4012/16 Diesel, February 1997 Section P7

From the library of Barrington Diesel Club
FUEL INJECTION SYSTEM

TO REASSEMBLE
Thoroughly wash all parts in clean fuel and
bring together without wiping. Carefully
reassemble the injector (Fig. 13P), taking
extreme care to ensure the dowels in the
transfer block (location adaptor) enter the
nozzle and element housing correctly and
the fuel feed and return holes are not
obstructed.
With the injector clamp Part No. T6253/146
held in a vice, slot the injector into the clamp.
Apply a light coating of grease to the nozzle
body clamping shoulder. This will lubricate
the clamping shoulder of the transfer block
(location adaptor) and nozzle body whilst
tightening the nozzle nut. Tighten the nozzle
nut by hand as far as possible, then using a
suitable torque wrench and a long 27 mm
socket, tighten the nozzle nut to the required
torque and test as described in Sections P9
to P11. (See Torque Settings pages 38-
40).
If the spray from the nozzle is defective
check under 'Injector Troubles' Section P9
and replace if necessary.
If the nozzle opening pressure is not within
the range specified, shims may be added or
taken away from above the injector spring to
increase or decrease the pressure.
Shims are supplied in various thicknesses
from 0.01 V to 0.80" (0.2794 mm to 2.0320
mm), so by careful selection small
adjustments in loading can be achieved e.g.
0.002" (0.0508 mm) increase in shim
thickness will give approximate pressure
increase of 5.2 bar (5.1035 atm) (75 lbf/in2)
5.273 kgf/cm2).
After testing as described in Section P10 to
P11 remove the injector from the fuel feed
adaptor and injector clamp (Fig. 10P), and
assemble the spring plunger assembly (Fig.
12P) to the element housing, ensuring that
the spring dowel (2) and timing pin (5)
engage with the spring plate locating collar
(3) as shown.

Section P8 4012/16 Diesel, February 1997

From the library of Barrington Diesel Club
 FUEL INJECTION SYSTEM

INJECTOR TROUBLES

SYMPTOMS POSSIBLE CAUSES REMEDY

Operating pressure too high or too low Wrongly set Readjust shims to obtain correct
operating pressure

Damaged or worn injector needle or Renew

nozzle

Incorrect needle or nozzle seating Renew

angles, giving incorrect seating line or no
angular difference

Restricted needle lift Renew nozzle assembly and/or thrust

spindle and upper spring

Nozzle holes clogged with carbon Clean nozzle or renew

Form of spray distorted Nozzle dirty and coated with carbon Clean

Damaged or eccentric seats Renew nozzle assembly

Out of true joint, faces between transfer Dismantle injector, clean and check joint
block, nozzie and element housing faces. Lap faces to obtain good even
caused by foreign matter between joint contact or renew components
faces or by fretting

Needle valve slack due to wear Renew nozzle assembly

Spray holes eroded Renew nozzle assembly

Needle valve damaged Renew nozzle assembly

Nozzle drips Carbon on valve seat Clean or replace with spare unit

Damaged or eccentric seats Renew nozzle assembly

Nozzle blueing Faulty fitting, tightening or cooling Renew nozzle assembly. Check cylinder
head coolant passages for scale deposits

Excessive leak-off (Pressure drop Needle valve slack Renew nozzle assembly
time less than 8 seconds)
'O' ring on fuel feed adaptor worn Check and renew 'O' ring

Foreign matter between face of nozzle Clean

body and transfer block or element
housing

Insufficient leak-off (Pressure drop Needle valve lacquered Clean nozzle assembly
time greater than 60 seconds)
Needle valve damaged Renew nozzle assembly

Fuel system gassing-loss of injection Faulty copper sealing washer allowing Renew copper sealing washer
to cylinder combustion gases to blow into fuel
system

Built up carbon not properly cleaned from Clean injector sleeve renew copper
bottom of injector sleeve preventing sealing washer and injector 'O' rings.
copper sealing washer seating

Nozzle needle sticking Clean thoroughly after inspection and

retest.

NOTE: Always test the injector immediately after cleaning the assembly.

4012/16 Diesel, February 1997 Section P9

From the library of Barrington Diesel Club
FUEL INJECTION SYSTEM

TO TEST AND SET THE INJECTOR

SETTING UP INJECTOR FOR TESTING
WHEN TESTING Ensure the reservoir of the nozzle
WARNING
A INJECTORS,
CARE MUST BE TAKEN TO PREVENT
'Testmaster' is filled with calibration fluid to
the correct level, which is half way up the
sight tube.
SKIN CONTACT WITH THE SPRAY,
SINCE THE WORKING PRESSURE
WILL CAUSE THE FLUID TO Key
PENETRATE THE SKIN, (Fig. 15P)
NECESSITATING IMMEDIATE 1 Illuminated spray chamber
HOSPITAL TREATMENT. THE SPRAY 2 Light switch
IS ALSO HIGHLY FLAMMABLE. 3 High pressure pipe
4 Clock
TEST OILS: The recommended test oils are 5 Pressure gauge
Shell Calibration fluid 'C' or 'B' or equivalent 6 Fuel control valve
fluids (Viscosity 38 Redwood No. 1 at 100°F/ 7 Gauge isolator
37.8°C). DO NOT use diesel fuel. 8 Switch for extractor fan on/off
9 Filler cap
To enable the operator to test the injector a 10 Fuel outlet
special tool assembly Part No. T6253/146 is 11 Hand lever
used. This consists of an injector clamp and 12 Sight tube
fuel feed adaptor (Fig. 10P) which is used in 13 Tank drain
conjunction with the recommended nozzle 14 Inclined support
Testmaster1(Fig. 15P) Part No. T6253/208. 15 Quick action clamp

Fig. 15P

Section P10 4012/16 Diesel, February 1997

From the library of Barrington Diesel Club
 FUEL INJECTION SYSTEM

Slot the injector into the injector clamp Part PRESSURE SETTING (REFER TO FIG. 15P)
No. T6253/146A with dowel fitting NOTE: A tolerance of ± 5 bar is permissible
uppermost. Grease the oil seal Part No. when adjusting the injector pressure setting
T6253/146B on the fuel feed adaptor and fit with shims (Refer to Section P8 for shim
the adaptor with a rotating pushing motion to data).
avoid damaging the oil seal, through the (a) Close the gauge isolator.
clamp into the element housing and lock in (b) Open the fuel control valve one full
position with the knurled nut (see Fig. 10P). turn.
NOTE: Oil seal Part No. T6253/146B usually (c) Switch on the extractor fan.
requires changing after 10/15 injector tests. (d) Operate the hand lever smartly until all
air is expelled from the injector.
Place the injector for testing loosely in the (e) Close the fuel control valve and set the
jaws of the quick action clamp (15) (Fig. gauge pointer to 'ZERO', then open the
15P) and connect the high pressure pipe (3) valve the minimum amount that will
to the fuel feed adaptor (Fig. 10P). Adjust allow the injector to operate when
the clamp on the inclined support (14) (Fig. pressing down hard on the hand lever.
15P) to position the injector nozzle tip inside Note reading on the scale.
the spray chamber (1). Tighten the clamp (f) Open the gauge isolator. Depress the
and ail pipe connections. hand lever and note the highest
pressure on the gauge before the
NOTES: nozzle 'pops', indicating needle valve
(1) The fuel control valve when closed opening. Adjust as necessary to 234
completely isolates the injector from bar (231 atm) (3400 lbf/in2) (23400
the hand pump. The degree of opening kPa), by adjustment of the shim
restricts the amount of test oil which thickness as described in Section P7.
can be delivered to the injector. (g) With the gauge isolator open, raise the
(2) The gauge isolator, when closed, pressure to approximately 220 bar (218
isolates the pressure gauge from the atm) (3200 lbf/in2). Release the hand
high pressure circuit, which eliminates lever and allow the pressure to fall
the damping effect of the gauge and naturally, timing the drop of the gauge
will prevent damage to- it when testing needle from 207 bar (204 atm) (3000
for atomisation and chatter. If pressure lbf/in2) (20700 kPa) to 138 bar (136
should become trapped in the gauge, atm) (2000 lb/in2) (13800 kPa). For a
release the gauge isolator a very small nozzle in good condition, this time
amount to let the pressure fall slowly. should be between 8 and 60 seconds
Only fingertip pressure is required to with the test oil at a temperature of
operate both this control and the fuel 68°C - 70°C (20°C - 21 °C).
control valve.

4012/16 Diesel, February 1997 Section P11

From the library of Barrington Diesel Club