diesel fuel injection pumps.docx
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Diesel Fuel Injection Pumps
Automotive diesel engines use two types of fuel injection pumps. One is an inline
cam-operated pump. It has a plunger for each engine cylinder. The other is a rotary
distri!utor-type pump. One or two plungers supply the fuel for all injection no""les.
Inline – Plunger Injection Pump
Figure F# shows an inline-plunger pump on a si$-cylinder diesel engine. The
pump has a !arrel-and-plunger assem!ly for each cylinder. An injection line or tu!e
connects each !arrel-and-plunger assem!ly to an injection no""le.
The construction of a !arrel-and-plunger assem!ly is shown in Figure F%. &ow-
pressure fuel from the fuel supply pump flows through the inlet port into the space
a!ove the plunger.
The plunger has a roller that rides on a cam on the camshaft. This is li'e the
roller tappets used in some engine valve trains. (hen the cam lo!e comes up under the
plunger the lo!e raises the plunger. This applies high pressure on the fuel trapped
a!ove the plunger.
The fuel is forced through the tu!e to the injection no""le in the cylinder where
the piston Is reaching TD) on the compression stro'e. The fuel sprays out and ignites
from the heat of the compression. The amount of fuel injected is varied !y varying the
effective stro'e of the plunger.
This is shown in Figure F%. The control rod connects !y lin'age through thegovernor to the accelerator pedal. As the driver depresses the pedal the lin'age causes
the control rod to move. This turns the plunger in its !arrel. The plunger has a groove
and an inclined heli$ machined into it
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Inline * Plunger Injection Pump
Turning the plunger for more fuel rotates the heli$ so a wider section faces the
inlet port. This closes the port for a longer time increasing the effective stro'e of the
plunger. Fuel delivery !egins when the top edge of the plunger closes off the inlet port.
Fuel delivery stops when the heli$ opens the inlet port.
The fuel-injection pump has a speed-advance mechanism. It advances the time
of injection as engine speed increases. This gives the fuel the necessary time to ignite
!urn and produce high pressure. (ithout injection advance wea' power stro'es result
at higher engine speeds.
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+otary Distri!utor Injection Pump
The distri!utor has two controls. One controls timing and the other controls the
amount of fuel injected. The timing device connects to the internal cam ring. This is the
cam on which the rollers roll. As engine speed increases the cam ring moves ahead.This causes the two plungers to move out and in earlier advancing the start of injection.
At the same time the internal governor regulates the amount of fuel delivered to the
cylinders.
Install , +emove the injection pump
&a!el the vacuum hoses and disconnect them from the
injection pump
&oosen the fuel filter union !olts and remove the one
connected to the injection pump.
+emove the delivery pipes connectedto the injection
pump delivery valvesand injection no""les.
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&oosen the !olts on the injectionpump cover. These !olts also
holdthe injection pump.
old and support the injection pumpwhile removing the
!olts.
Pull out the injection pump from the cover.
et the injection timing
+emove the timing mar' cover.
Find the mar's on the idler gear andthe injection pump gear.
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+eturn the injection pump and align the timing mar's of the injection
pump gear and the idler gear.
Inspect the position of the injection pump gear timing mar'. It must !e
!etween the idler gear timing mar's.
Install the !olts holding the injection pump and tighten.
+eturn the timing mar' cover.
Timing Device
The timing device usually consists of an aluminum casting (ith /ounting flanges
at !oth ends. A !ore in the housing guides and supports the spider assem!ly. A timing
opening with a cover is located in the top of the housing and is used to o!serve the
position of the timing pointer in relation to the timing mar' on the timing device hu!
during injection pump timing procedures.
The timing device hu! with e$ternal left-hand helical spines for engaging the
internal helical spines of the sliding gear has a tapered !ore and 'eyway. The hu! is
secured to the camshaft e$tension !y a woodruff 'ey nut and setscrew. The hu! is
usually counter !ored to receive the timing device springs. The springs oppose the
flyweight forces of the weight and spider assem!ly.
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The weight and spider assem!ly has e$ternal right-hand helical spines which
mesh with the internal helical spines of the sliding gear. The splinted end is machined to
receive the end play spacer. Three flyweights are pinned to a flange adjacent to the
splints. The weight and spider thrust plate located !etween the flange and the timing
device housing carries the !ac' thrust of the flyweights and prevents housing wear.
Operation
%. As the engine rotates the weight and spider assem!ly centrifugal force opensthe flyweights from their collapsed position against the force of the three timing devicesprings.
0. As the flyweights swing out the sliding gear isforced toward the timing devicehu!.
1. The longitudinal movement of the sliding gear on its helical splint causes a slight
change in the rotational relationship of the injection pump to the engine causinginjection to !egin slightly earlier in the power stro'e.
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Timing the Fuel Injection Pump
2ote3 4nless major repair wor' is done on the engine timing should not !e
re5uired.
Four cylinder firing order - % - 1 - 6 - 0
Procedure:
%. +emove fuel lines from injector pump fittings on injector pump.0. Pull the decompression lever so that it will remain in the decompression position.
2o decompression lever on /odel-%01. Open throttle fully.6. 7nergi"e the electric fuel pump and turn engine over with starter to ensure that
fuel is coming out of each injector pump opening. ave clean rags around opening tosoa' up fuel.
8. (ipe off any fuel on injector pump !ody and the top of each injector opening.9. Turn cran'shaft over !y hand !eing careful not to damage splint on end of
cran'shaft. 7ngine rotation will !e cloc'wise. TOP I//7DIAT7&: at the first sign offuel movement in the injector pump fuel fitting for whichever injector pump is !eingchec'ed. ;2o. % injector pump is the closest to the . +emove the cover from flywheel timing mar' inspection hold located inside of leftengine mount.
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?. )hec' alignment of mar' on flywheel with the timing pointer on the wall of theinspection hole. The %-Fl mar' on the flywheel represents fuel injection of 2o. %cylinder. 0-Fl represents 2o. 0 cylinder etc.
@. If timing pointer and the flywheel mar'ing %-Fl is aligned then 2o. % cylinder isproperly timed for fuel injection and should re5uire no adjustment. The same will !e
true for 2o. 0 2o. 1 and 2o. 6 cylinders if the a!ove steps are followed.%#. In order to determine if timing is off or if the injection pump is faulty it isnecessary to rechec' the timing for each cylinder two or three times.
%%. If there are variations in repeata!ility in the alignment of pointer and timing mar'a faulty fuel injector pump may !e suspected.
%0. If timing mar's repeat to same location !ut are off 1,%9 or more a!ove or !elowthe pointer this indicates that the engine must !e retimed.
If alignment of the timing mar' is not within 1,%9 a!ove or !elow the pointer the
a!ove steps must !e ta'en to time the engine. If the timing is found to !e satisfactory
then reconnect all fuel lines and fittings and tighten. The fuel system must !e !led
!efore the engine will operate properly.
)hec'ing the Injection 2o""le
2ote3 2ever remove an injection no""le from the engine e$cept for service or
replacement.
The following indicate injection-no""le trou!le3
B One or more cylinder 'noc'ing.
B &oss of power.
B mo'y !lac' e$haust.
B 7ngine overheating.
B 7$cessive fuel consumption.
Procedure:
%. One way to chec' injection no""les is to run the engine at fast idle.0. &oosen the connector at each no""le in turn one at a time.
1. (rap a cloth around the connection !efore you loosen it to 'eep fuel from
spurting out. If loosening the connector causes engine speed to drop the no""le is
pro!a!ly wor'ing normally. If the engine speed remains the same the no""le is not
wor'ing properly. )logged holes are preventing fuel delivery or causing an improper
spray pattern. ome manufacturers recommend a spray test of the detached
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injection no""le. This re5uires a no""le tester which is a special hydraulic pump and
pressure gauge.
6. Attach the no""le and apply pressure. The fuel should spray in an accepta!le
pattern when the specified pressure is reached.
8. +eleasing the pressure should stop the spray a!ruptly without any drip from the
no""le.
Caution: Direct the spray from the no""le into a suita!le container. Do not allow
the spray to hit your s'in. The pressure is high enough to force fuel oil through the s'in.
:ou can !e seriously injured !ecause the oil could cause an infection. If the engine
misses at all speeds and produces a puff of e$haust smo'e each time it misfires an
injection no""le is pro!a!ly stic'ing open. The no""le can !e disassem!led and
cleaned. omemanufacturers recommend replacing a faulty no""le.
Caution: If you disassem!le a no""le do not damage the tip or enlarge the
holes. This can cause lea'age and other trou!les
Cleeding the Fuel ystemIt is necessary to !leed the fuel system to achieve a steady air free flow of fuel if
any of the following has occurred3
• +unning out of fuel.
• If fuel shut off valve is left closed and engine runs out of fuel.
• +eplacing fuel filter.
• Fuel injector no""le or injector pump repair.
• After repairing or replacing any fuel line.
•Cefore putting engine !ac' into service in the spring if fuel system has !een
drained.
• +eplacement of electric or mechanical fuel pump.
• Any time air is permitted to enter the fuel system..
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Cleeding Procedure
Ce sure to have some means availa!le to catch or a!sor! any fuel escaping
during the !leeding process so that it will not accumulate in the engine compartment or
!ilge.
%. Ce sure there is a sufficient supply of fuel in the fuel tan'.
0. Open the fuel shut-off valve at the tan'.
1. tart the electric fuel pump !y turning the ignition 'ey to the O2 position
onmodels %? 0# 08 1# 8# all models after %@?9.
6. /odel %8 has a mechanical fuel pump. Therefore with decompression on
turnengine over with starter. )ran' at %# second intervals while doing steps 8 and
>.
8. lowly loosen the air !leed plug on the fuel filter letting air escape until an air
free flow of fuel is evident. .
9. At this time tighten the air !leed plug on the filter.>. lowly loosen the air !leed plug on the injector pump letting air escape until an
air free flow of fuel is evident. 4nits with a self !leed return valve open for a short
period then start engine as soon as engine runs smooth close valve. /odel-%0 has
continuous fuel !leeding.
?. At this time tighten the air !leed plug or 'nurled 'no! on the injector pump.
@. The fuel system should now !e properly !led and ready for operation. +efer tvo
starting instructions !efore attempting to start the engine after !leeding the fuel
system.