TM 9-4910-677-14&P

TECHNICAL MANUAL

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE MANUAL INCLUDING REPAIR PARTS LIST

FOR

TESTER, INTERNAL COMBUSTION ENGINE MODEL 27-12 (CENTURY TOOL COMPANY, INC.) (NSN 4910-00-255-8673)

HEADQUARTERS, DEPARTMENT OF THE ARMY

MAY 1980

TM 9-4910-677-14&P

Technical Manual HEADQUARTERS DEPARTMENT OF THE ARMY No. 9-4910-677-14&P Washington, DC, 9 May 1980

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE MANUAL INCLUDING REPAIR PARTS LIST FOR TESTER, INTERNAL COMBUSTION ENGINE MODEL 27-12 (CENTURY TOOL COMPANY, INC.) (NSN 4910-00-255-8673)

REPORTING OF ERRORS

You can help improve this manual by recommending improvements using, DA Form 2028 (Recommended Changes to Publications and Blank Forms) or DA Form 2028-2 located in the back of this manual. Mail your form direct to Commander, US Army Armament Materiel Readiness Command, ATTN: DRSAR-MAS, Rock Island, IL 61299. A reply will be furnished direct to you.

NOTE

This manual is published for the purpose of identifying an authorized commercial manual for the use of the personnel to whom this tester- is issued.

Manufactured by: CENTURY TOOL COMPANY, INC. Hilton Street Easton, PA 18042

Procured under Contract No: DAAA09-76-C-6699

This technical manual is an authentication of the manufacturers’ commercial literature and does not conform with the format and content specified in AR 310- 3, Military Publications. This technical manual does, however, contain available information that is essential to the operation and maintenance of the equipment.

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TESTER, INTERNAL COMBUSTION ENGINE

Pairs of cylinders can be placed under load by shorting out the plugs of the other cylinders after opening the throttle valve and locking it in place. If two cylinders are able to run the engine against the compres- sion of the others, it indicates that the ignition is not missing, that the carburetor high speed and power circuits are working and that com- pression must be at least in fair condition. Compare the vacuum readings while running on different pairs of cylinders.

The vacuum gauge is an accu- On 4 cylinder engines, set the rate means of adjusting ignition throttle so the engine will run about timing. With the motor at a fast 900 RPM with all cylinders operating. idle, advance the ignition timing so Then run on the following pairs with as to get the highest possible steady the other cylinders grounded out. reading on the vacuum gauge. Now Run on cyl. 1 and 4. Run on cyl. 2 and 3 retard so that the needle on the gauge just begins to drop. Now the question of detonation or ping On 6 cylinder engines fix the enters the picture. If the cooling throttle at about 1000 RPM with all system is functioning properly, the cylinders operating Then run on spark plugs are not too hot, the com- the following pairs with the remain- bustion chamber is not insulated by ing cylinders grounded out. a carbon mixture, the carburetor Run on cyl. 1 and 6 Run on cyl. 2 and 5 mixture is right, and the mixture from the carburetor has the proper Run on cyl. 3 and 4 turbulence in the combustion chain. ber, this is the proper timing posi- On 8 cylinder- engines fix the tion. Unfortunately, in many in- throttle at about 1500 RPM running stances, one or more of the above on all cylinders. Then run on the mentioned conditions exist, and we following pairs with the other cyl- must set the ignition timing to com- inders grounded out. pensate for them. To do this, short Run on cyl. 1 and 8 Run on cyl. 3 and 6 out the cylinders by clipping the dif- ferent leads to the spark plugs until Run on cyl. 2 and 7 Run on cyl. 4 and 5 the motor is working on two cyl- inders. We are now able to dup- The manufacturers of V-8 en- licate a load tendency of the gines use several different methods motor to detonate or ping. Re- of numbering the cylinders. To tard the timing till the motor does decrease the confusion a lettering not ping, and the timing is now system (see illustration) has been set to eliminate detonation. developed

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which applies to all V-8 engines re- 4. It the pointer is unsteady and if gardless of which cylinder the manu- the sweeps of the pointer increase facturer has designated as number with increases in speed, the trouble one. On V-8 engines, ground out all is weak or broken valve springs. If the other cylinders and run on the the sweeps get smaller but more following pairs. rapid on increasing the speed, the Run on cyl. A and F Run on cyl. D and G trouble is in intake system leaks. If the pointer steadies on increasing Run on cyl. Band H Run on cyl. C and E speed, the trouble is ignition, faulty distributor weights, or carburetion.

5. This is a normal reaction when the throttle valve is opened and closed. If the pointer does not re- spond with wide sweeps, it is an in- dication that leakage exists. If the possibilities of leakage through poor1y seating valves, manifolds, gaskets, etc. have been exhausted, 1. When the pointer is low but then the piston rings are not seal- steady, the trouble is something ing properly. which affects all cylinders alike. This could be late ignition timing, 6. (1) When the distributor is ad- late valve timing, or loose tappets. vanced to the highest steady reading Such troubles can be responsible for and then retarded so the pointer is the reading being anywhere from1/4 1/4 to1/2 inch below the highest steady to 2 inches low. Intake system leaks reading, and (2) if the pointer is (warped intake manifold, leaky within specifications and holding manifold gasket, leaky carburetor steady after making this adjustment flange gasket, poorly seating intake and (3) if the ignition is in time after valves and leaky intake guides) can checking with a timing light after be responsible for the reading being making this adjustment, the engine anywhere from 1/4 to 16 inches low can be considered to be in time. depending on the size of the leak. Allow one inch less for each 1000 feet of elevation. 2. When the pointer pulses regu- larly, the trouble is something which NORMAL REACTIONS affects one particular cylinder con- sistently; for instance, one exhaust, 18 to 22 inches is usually referred valve which does not seat, one ex- to as the normal range for a warmed haust tappet which is too tight, or up engine at idle speed, but with one sticky valve, or one dead spark greater and greater degrees of valve plug. The pulses of the pointer are overlap, this range is becoming much greater if they are caused by meaningless. Some car manufac- some form of leakage such as ex- turers are now specifying 15 inches haust valve not seating, rather than as a noamal vacuum reading during something which, only slows the pis- engine idle. The specifications for tons such as a dead spark plug. the car under test should be checked. If with proper tune-up a particular 3. An unsteady pointer may be engine could be adjusted to 21 inches caused by defects occuring irregu- of vacuum, it would be considerably larly and in several or all of the cyl- out of time if the vacuum were ad- inders. Other defects which are justed to only 19 inches; despite the responsible for an unsteady pointer fact that 19 is within the so called are loose distributor governor normal range. springs, rich carburetor mixture, extremely advanced or retarded To adjust ignition timing with a spark, wide spark plug gaps, igni- vacuum gauge, loosen the distributor tion points not synchronized, or in- setscrew and advance to the highest take valves shifting on their seats. STEADY reading. Then retard 2 TM 9-4910-677-14 & P

enough so the reading is 1/4 to 1/2 inch Just as a vacuum gauge may be below the highest steady reading. used to adjust ignition timing, it An intake system leak will also lower may also be used, in much the same the reading but it may be so small manner, to adjust the idle screw in a that the pointer may still be within carburetor by richening the mixture the so called normal range. More to the highest steady reading. Thus, will be said about intake system a faulty carburetor adjustment will leaks and timing later, but at the affect the vacuum reading. moment, we wish to emphasize (1) that the higher the vacuum gauge Valve timing too, affects vacuum reading, the better; provided the ig- gauge readings. Valve timing can be nition is not so far advanced that the late because of improper installation engine pings under normal accel- of timing gears but more common eration and (2) that an engine is not than this, tappets are set too loose necessarily in perfect working order causing the valves to open late (and just because the vacuum reading is close too early). This condition within the so called normal range on would reduce power considerably. the gauge. Consequently, the speed of the pis- tons would be slowed and this would Normal steadiness of the gauge be still another reason why the vac- pointer varies according to the num- uum gauge reading might be low. ber of cylinders in the engine. On four cylinder engines, the intake Speed of the pistons will be slowed strokes do not overlap. The vacuum by anything that reduces power, such gauge responds to this with an even as shorted spark plugs, leaky igni- rippling motion of the pointer. On tion wires, or any of a number of six cylinder engines, there is only ignition difficulties which may a faint trace of this rippling and on ground out a cylinder. To learn the 8 cylinder engines, it is almost non- effect of a dead cylinder, connect existent, except on engines which the vacuum gauge to an engine and have overlapping valve timintg. The short out first one, then two spark best way to become familiar with a plugs, etc. and study the effect. You normal steady reading is to connect may be surprised by the small re- the gauge to engines known to be in duction in speed and vacuum at idle good operating condition and then to speed by shorting out only one cyl- study the readings. inder, especially on an 8 cylinder engine. The reduction is greater on Responses of the gauge to move- a 6 cylinder engine and quite notice- ments of the throttle valve are much able on a 4 cylinder engine. more exaggerated in a driving test than in a floor test, but in either REACTION TO LEAKAGE case, the vacuum will fall off when It should be understandable that the throttle is suddenly opened and a leak in any of the passageways be- it will rise when the throttle is sud- tween the carburetor and the cyl- denly closed. In a floor test, it is inders will interfere with the flow of normal for the pointer to oscillate air and fuel from the carburetor to between approximately 3 and 25 the cylinders. Defects of this nature inches as the throttle is suddenly affect the speed of the pistons too; opened and closed. If the vacuum but much more directly they inter- gauge does not respond in this way, fere with the actual creation of the it is an indication that leakage exists vacuum. A leak in the manifold either in the form of poorly seating gasket (depending on its size) can be valves or in the form of poorly seal- responsible for a reading anywhere ing piston rings. from slightly above zero to slightly REATION TO SPEED CHANGES below normal. Leakage into the manifold has much more effect on A low reading on the gauge may the gauge reading than defects that indicate late ignition timing. A high affect speed only. A very tiny leak unsteady reading may indicate ad- will lower the vacuum reading con- vanced timing: siderably.

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(Leakage leans the mixture. When it is fairly wide sweeps. Other defects excessive, it burns the valves and spark which DO NOT affect all cylinders plugs prematurely. Even in its mildest equally are a worn exhaust valve form, it causes an engine to ping. It should be noted that compensation can be guide, a piston ring that does not made in mild cases of leakage by re- seal, a leaky spark plug gasket, etc. tarding the spark. When this is done, the engine will not develop quite as much UNSTEADY POINTER power or have quite as good mileage as when the leakage is corrected and the If the pointer moves in wide timing advanced to where it should be. When adjusting the ignition timing with sweeps of 3 or 4 inches, the trouble a vacuum gauge as explained previously, could be a blown head gasket between leakage is automatically compensated two cylinders or ignition cross firing for. Or looking at it another way; if the because of insulation breaking down vacuum gauge setting is later than the either in the distributor or in the timing light setting it usually indicates spark plug cables. The trouble that intake system leakage exists. There could also be weak valve springs. are other reasons, however, why it is sometimes necessary to retard the spark To determine whether or not the from the timing light setting to prevent a trouble is due to cross firing, one ping. Sometimes it is because of low plug at a time may be shorted out to octane gasoline or because of com- determine which is firing its cyl- pression being too high). inder at the wrong time. The sweep- ingaction will stop when the offend- Intake system leakage is not only ing plug is shorted out. found in the form of a leaky manifold gasket. It might be in the form of a Distributor governor weight warped or loos e intake manifold, movements are sometimes very leaky carburetor flange gasket, worn critical at low engine speeds because throttle shaft, one or more poorly there is no spring tension on them; seating intake valves (for any rea- and often they cause a continual but son including a tight tappet), one or very slight change in engine speed by more worn intake valve guides, or moving in and out. This action causes leaks in any of the lines or fittings a continual advance and retard of the to any vacuum operated units such as spark, in turn, causing the pointer windshield wipers, etc. All of these on the gauge to be unsteady. The defects affect all cylinders equally pointer may react much the same so all of them cause the vacuum way if the spark is advanced beyond. gauge to give a low but steady read- the highest steady reading. ing. How low the reading depends on the size of the leak. An unsteady action of the pointer may also be caused by unevenly or There are other types of leakage widely spaced spark plug gaps or by which DO NOT affect all cylinders spark plugs that are carbonized from alike and therefore DO NOT give a a rich mixture or from oil; or just steady reading on the vacuum gauge. because they are too cold for the A poorly seating exhaust valve, for engine. An unsteady pointer may al- instance, would affect the intake only so be the result of small inconsistent for one cylinder. Every time the in- intake system leaks, such as intake take valve for that cylinder would valves shifting on their seats be- open (on the intake stroke of the pis- cause of worn guides or such as a ton) exhaust gas would be drawn into worn throttle shaft in a carburetor. that cylinder. This momentary re- Ignition points that are not synchron- duction in vacuum would react on the ized, insufficient tappet clearance, gauge as a large pulse of 2 to 4 inches weak valve springs and sticky valves and much larger than the pulses also cause the pointer of the gauge to caused by shorting out a cylinder. be unsteady. Of course, the size of the pulse de- pends on the size of the leak and Often the trouble may be isolated where more than ore cylinder is con- by adjustment of the timing and the cerned, the pulses change to an carburetor and a check of the ignition erratic wandering of the pointer in circuit including inspection of the

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plugs. If further isolation is nec- horn (after removing the alr clean- essary, the engine speed should be el.). A vacuurrj gauge reading during increased to what would be about 12 cranking of at least 17 inches irldl- or 15 MPH. The higher speed re- cates the Intake system to be fairly duces the effect of a rich mixture, well sea~d, but the higher the read- puts tension on the governor weights ing, the better if” the reading is and decreases the effect of small low, it should IJC det., rrnined whether Intake system leaks. At the same the leak is Lrlthe ,a~’luretor or ln the time, it increases the effect of bad engine. To do this, the carburetor valve action. should be rt, moved and the test made again, but this time with the mouth (A) On this faster engine speed, of the manifold cover edwlth the hand if the pointer steadies, the trouble or with some kind of a stopper. If is ignition, car buretion, faulty dis- a h~gher reading is obtained by the tributor weights or advanced latter test, then the leak is in the timing. car buret(,, P(,sslblya worn throttle shaft, a poor vacu,~lm llr]e, a leaky (B)If the sweeps get larger with flange gasket or a cracked casting further increas es in speed, the woul(i b(, the sourct, of the trouble. trouble is definitely weak or brokerl With the engine ru~ning, Intake sys- valve springs. tem leaks may be detected by squirting oil around w he r e leaks (C)When the sw eeps becon]e could exist. If a leak is present, the shorter and more rapid on the 111- oil disapp[,ars :r]to the leak. A leak creased engine speed, the trouble between the intake and exhaust manif- could be slight intake sjstcm leaks. olds ~rl the heat rl~cr 1s difficult to Such leaks could b e duc iu sticky i[~catc kjy any othtf m e t h od than valves or insufficient tappet clear- (,lirr~lr~atlc)[l of {)th[~l pc~ssi billties or ance. Tappet clearances can k>e by direct [,xamlllatlon. checked and sticking valves car] b~ eliminated in most cases, at least If t}iv t~(,ubl< c.~rlnot IIP !ocated temporarily, by the intr-oductlon of witl, the rt, asonlng of the previous oil through the intake system or by paragra}>hs a]ded by your previous applying Lt directly t o t h e guides expcrlence, in a kf a cylinder bal - where possible. ancf test tc is elate the trouble further. A cyllnder balance test is LOW READING also useful In detf, rmlning the gener- al condition of an englrre. A low reading can often be ccr - rected too, Ly adju:, ting the lgnltion timing. If it cannot be corrected in this manner, concentrate on finding COLD ENGINE TESTING an intake system leak. Head gasket leaks to the outside atmosphere can T o make a satisfactory engine be located by running the engine and analysis with a vacuum gauge, the listening for the escape of the burned engine must be at operating temper- gases. If the escape is suspected to ature because there area great many be through the spark plug, the plug defects p r e s ent in a cold engine should be examined closely for which correct themselves after op- streaks. If the head gasket is blown erating temperature is reached. An between two cylinders or if the ex- engine which is cold must be capable haust valves do not seal properly, a of developing a t least 7 inches of compression gauge test will reveal vacuum in the intake manifold while the cylinders at fault. cranking t o guarantee a sufficient flow of f ue 1 into the cylinders to T o determine i f intake system start the engine. Sometimes, an leaks are present, the ignition should engine cannot develop vacuum and be shut off and the engine cranked will not start because of lack of oil with the starter while the hand is around the piston rings or because of held tightly over the carhl]retor air a large intake system leak.

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VACUUM BOOSTER PUMP LIFT TEST Disconnect both sides of the pump With the ignition switch in the and connect the vacuum gauge on the Off position, the throttle closed wiper side. The reading should be tightly, use the starting motor to steady between 7 and 12 inches. A turn the motor and note the indicator ruptured diaphragm may cause high reading. It should read between 8 oil consumption, poor engine idle or and 14 inches. Failure to do so in- fouling of spark plugs on one side of dicates an open intake due to the the engine. butterfly not closing properly, a leaky intake manifold gasket or CHOKED MUFFLER burnt heat risers. Accelerate the motor quickly several times in rapid succession. CHOKE TEST With a clear muffler the indicator Open throttle, close the choke, needle has a quick return to nor- and step on the starter. The gauge mal each time while with a clogged should read, at least, 2 inches, or muffler, the indicator needle will as high as 6 inches depending on the have a tendency to be sluggish and, type of choke. If you cannot get the in severe cases, will not raise be- desired reading, the choke valve is yond 8 inches and will show excess- not closing properly which usually ive vibration. causes hard starting. FUEL PUMP TESTER PRESSURE TEST If these readings are not obtained, To make a fuel pump pressure pump repairs are necessary. test, remove the gas line from the pump to the carburetor at the fuel FUEL FLOW TEST pump. Remove the 1/8" pipe fitting To determine if gas line or gas from the pump. Insert the 1/8" pipe tank is clogged, connect T fitting fitting supplied with the analyzer and between fuel pump and line to gas fasten the hose from the pressure tank. Attach hose from gauge to re- gauge to it. Make sure the fittings maining nipple of tee. Operate the are all air tight. Operate the motor motor at 10 to 15 miles per hour. If at 10 to 15 miles per hour. The gas line and tank cap are clear, the reading on the gauge should be not gauge reading will fluctuate between less than 2, and not more than 3-1/2 0 and 1 inch of vacuum, and steady pounds; and not less than 1/2 pound reading above one inch of vacuum on wide open throttle. If these read- indicating partially or wholly ob- ings are not obtained, pump repairs structed gas line or tank cap. are necessary. On late model Olds- mobile - 6 cylinder - specifications MUFFLER BACK PRESSURE TEST call for 4-1/2 pounds maximum. On To make a muffler back pressure the 8 cylinder, 3-1/4 pounds maximum. test, it is necessary to drill and tap for 1/8" pipe fitting in the exhaust VACUUM TEST manifold, as near the muffler pipe To make a fuel pump vacuum test, flange as possible. Insert the 1/8" remove the gas line from the pump pipe fitting and attach the hose lead- and, using the proper adapter sup- ing to the pressure gauge. Start the plied, attach the hose of the vacuum motor. If a pressure of 3 pounds or gauge. Operate the motor to 10 to more s shown, the muffler must be 15 miles per hour. The reading on replaced. Motor speed to be approx- the gauge should be 8 or more inches. imately 50 miles per hour. ALTITUDE COMPENSATOR FOR VACUUM GAUGE Altitude From Atmospheric Vacuum Gauge Sea Level Pressure Reading - Normal Motor Sea Level 14.7 18 1000 Feet 14.1 16 2000 Feet 13.6 14 3000 Feet 13.1 13.5 4000 Feet 12.5 13 5000 Feet 12.3 12.5

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PARTS LIST MODEL NO. 27-12 VACUUM TESTER

DESCRIPTION QTY. REQUIRED VACUUM GAGE 1 ea. HOSE, 50” LONG, V4 “ I.D. 1 ea. ADAPTER SET 3/8-24 NF-2 INVERTED FLARE FEJvIALE 1 ea. 7/16-24 N$2 LNVERTED FLARE FEMALE 1 ea. 1 /2-20 NF-2 INVERTED FLARE FEMALE 1 ea. 1 /2-20 NF-2 FLARED MALE 1 ea. 5/16-24 NF-2 FLARED MAI.E 1 ea. 1 /8-27 MALE 1 ea. 1/4-18 MALE 1 ea. 3/8-18 MALE 1 ea. CARRYING CASE 1 ea.

GAUGE MUST BE ADJUSTED TO ZERO BEFORE USING.

7 By Order of the Secretary of the Army:

E. C. MEYER General, United States Army Official: Chief of Staff

J.C. PENNINGTON Major General, United States Army The Adjutant General

U.S. GOVERNMENT PRINTING OFFICE: 1982 O - 388-960

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