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1-13TX / TXH / TXB 180S - 400L (Rev. 4/23/07)TX / TXH / TXB 180S - 400L (Rev. 4/23/07)
Engine Engine TTroubleshootingroubleshooting
The following chart includes some of the problemsThe following chart includes some of the problems
that an operator may encounter during the servicethat an operator may encounter during the service
life of a life of a Cummins diesel Cummins diesel engine. engine. Always checkAlways check
the easiest and obvious things first, such as thethe easiest and obvious things first, such as the
master disconnect switch, the neutral start switch,master disconnect switch, the neutral start switch,
an empty fuel tank, closed fuel shut off, dead bat-an empty fuel tank, closed fuel shut off, dead bat-
tery or tery or corroded terminals. corroded terminals. Study the Study the problemproblem
thoroughly before starting to work on the engine.thoroughly before starting to work on the engine.
Ask yourself Ask yourself the following the following questions.questions.
1.1. WhaWhat wert were the we the warnarning sing signigns pres precedceding ting thehe
trouble?trouble?
2.2. Has tHas the enhe engingine beee been subn subjecjected tted to reco recentent
repair or maintenance?repair or maintenance?
3.3. Has a Has a simsimilailar tror troubluble occe occurrurred beed beforfore?e?
4.4. If tIf the engihe engine stne still rill runs, uns, is it is it safe safe to coto continuentinue
operation of the engine in an effort to diag-operation of the engine in an effort to diag-
nose the trouble?nose the trouble?
Check the items most easily and inexpensively cor-Check the items most easily and inexpensively cor-
rected before proceeding to the more difficult, timerected before proceeding to the more difficult, time
consuming and expensiconsuming and expensive itemsve items. . After a After a malfunc-malfunc-
tion has been corrected, locate and correct thetion has been corrected, locate and correct the
cause of the trouble to prevent recurrence of thecause of the trouble to prevent recurrence of the
same trouble.same trouble.
Engine Noise Diagnostic Procedures – GeneralEngine Noise Diagnostic Procedures – General
InformationInformation
NOTE:NOTE: When diagnosing When diagnosing engine noise engine noise problems,problems,
make sure that make sure that noises caused by noises caused by accessories,accessories,
such as the such as the air compressor and air compressor and power take–off,power take–off,
are not mistaken are not mistaken for engine noises. for engine noises. Remove theRemove the
accessory drive belts to accessory drive belts to eliminate noise caused eliminate noise caused byby
these units. these units. Noise will Noise will also travel also travel to other mto other metaletal
parts not related to parts not related to the problem. the problem. The use of aThe use of a
stethoscope can stethoscope can help locate help locate an engine an engine noise.noise.
Engine noises heard at the crankshaft speed,Engine noises heard at the crankshaft speed,
engine rpm, are noises related to the crankshaft,engine rpm, are noises related to the crankshaft,
rods, pistons, rods, pistons, and piston and piston pins. pins. Noises heard Noises heard atat
the camshaft speed, one–half of the engine rpm,the camshaft speed, one–half of the engine rpm,
are related to are related to the valve the valve train. train. A handheld digitalA handheld digital
tachometer can help determine if the noise istachometer can help determine if the noise is
related to components operating at the crankshaftrelated to components operating at the crankshaft
or camshaft speed.or camshaft speed.
There is not a definite rule or test that will positive-There is not a definite rule or test that will positive-
ly determine the source of a noise complaint.ly determine the source of a noise complaint.
Engine–driven components and accessories, suchEngine–driven components and accessories, such
as gear–driven fan clutches, hydraulic pumps,as gear–driven fan clutches, hydraulic pumps,
belt–driven alternators, air–conditioning compres-belt–driven alternators, air–conditioning compres-
sors, and turbochargers, can contribute to enginesors, and turbochargers, can contribute to engine
noise. noise. Use the followUse the following information as ing information as a guide toa guide to
diagnosing engine noise.diagnosing engine noise.
Main Bearing NoiseMain Bearing Noise (Refer to Problem 40.)(Refer to Problem 40.).. TheThe
noise caused by a loose main bearing is a loud,noise caused by a loose main bearing is a loud,
dull knock heard when the engine is pulling adull knock heard when the engine is pulling a
load. load. If all mIf all main bearings are ain bearings are loose, a loud loose, a loud clatterclatter
will be heard. will be heard. The knock The knock is heard regularly is heard regularly everyevery
other revolution. other revolution. The noise The noise is the is the loudest whenloudest when
the engine is the engine is lugging or under lugging or under heavy load. heavy load. TheThe
knock is knock is duller than duller than a connecting a connecting rod noise. rod noise. LowLow
oil pressure can also accompany this condition.oil pressure can also accompany this condition.
If the bearing is not loose enough to produce aIf the bearing is not loose enough to produce a
knock by itself, the bearing can knock if the oil isknock by itself, the bearing can knock if the oil is
too thin or if there is no oil on the bearing.too thin or if there is no oil on the bearing.
An irregular An irregular noise can noise can indicate worn crankshaftindicate worn crankshaft
thrust bearings.thrust bearings.
An intermittent, sharp An intermittent, sharp knock indicates excessiveknock indicates excessive
crankshaft crankshaft end clearance. end clearance. Repeated clutcRepeated clutch disen-h disen-
gagements can cause a change in the noise.gagements can cause a change in the noise.
Connecting Rod Bearing NoiseConnecting Rod Bearing Noise (Refer to Prob-(Refer to Prob-
lem 39.)lem 39.).. Connecting rods with excessive clear-Connecting rods with excessive clear-
ance will knock at all engine speeds under bothance will knock at all engine speeds under both
idle and idle and load conditions. load conditions. When the When the bearingsbearings
begin to become loose, the noise can be con-begin to become loose, the noise can be con-
fused with pistfused with piston slap or on slap or loose piston pins. loose piston pins. TheThe
noise increases in volume with engine speed.noise increases in volume with engine speed.
Low oil pressure can also accompany thisLow oil pressure can also accompany this
condition.condition.
Piston NoisePiston Noise (Refer to Problem 41.)(Refer to Problem 41.).. It is difficultIt is difficult
to tell the difference between piston pin, connect-to tell the difference between piston pin, connect-
ing rod, and ing rod, and piston noise. piston noise. A loose A loose piston pinpiston pin
causes a loud double knock that is usually heardcauses a loud double knock that is usually heard
when the when the engine is engine is idling. idling. When the When the injector toinjector to
this cylinder is cut out, a noticeable change will bethis cylinder is cut out, a noticeable change will be
heard in the heard in the sound of sound of the knocking the knocking noise. noise. Howev-Howev-
er, on some engines the knock becomes moreer, on some engines the knock becomes more
noticeable when the vehicle is operated on thenoticeable when the vehicle is operated on the
road at a steady speed.road at a steady speed.
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