Snap-on Mt2261a Manual 2l6py

MT2261A Computerized Tach/Advance Timing Light

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MT2261 Computerized Tach/Advance Timing light

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-. MT2261 AComputerized Tach/Advance Timing light

is displayed momentarily when / / (Reset) is pressed. / / (Reset) is also used to clear and restart the timing light if erroneous data is displayed.

Specifications Operating Temperature Range .............. -40·F to 149·F HO·C to 65·C) Power Requirement ...................... 10 to 16 Volts DC Useable Range ............................ 30 to 9,990 RPM Timing Advance Range ........................ O· to +180·

Functional Description POWER LEADS have color-coded clip boots. Red lead connects to positive (+) terminal of 12 volt battery and black to a good vehicle ground. INDUCTIVE PICKUP clamps over #1 cylinder spark plug wire (usually - see Equipment & Testing Tips #10) to monitor high voltage surges. Its signal controls the light flashes and is used for computing the RPM and timing reading. LED DISPLAY displays engine speed from 0 to 9990 RPM and timing degrees from O· to +180·. "Err" will be displayed if RPM exceeds 9990. CONTROL has the following five function keys: (;i,;)lj (Tach/Advance) is depressed to select tachometer

or timing reading.

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(Flash) is an "ON-OFF" switch for the flash function. ~

(Increase) increases degrees oftiming light advance up to 180·. After key is depressed one second, the MT2261 A begins rapid advance. ~ (Decrease) decreases degrees of timing light advance that have been entered. It operates in the same manner as the ~ (Increase) key. Pressing ->-(Decrease) when display reads "0" sets timing light to 180· advance.

/ / (Reset) automatically zeroes degrees of advance that have been entered with the ~ (Increase) key. "2261"

Equipment & Testing Tips 1. The MT2261 A Computerized Tach/Advance TIming Light can be powered by a negative or positive ground 12 volt DC power source. If the test vehicle has a different electrical system (6 or 24 volt system, etc), an auxiliary 12 volt battery may be used to power the timing light. If the battery terminals are difficult to access, an auxiliary battery may be used, or you can connect the positive lead to the alternator output terminal and the negative lead to a good vehicle ground.

2. If the MT2261 A fails to operate, check power leads for good connections and the proper polarity, make sure inductive pickup jaws are firmly seated and that latch is in the lock position, and inspect inductive pickup's ferrite cores for cleanliness and damage. CAUTION: Do not allow core pieces to metal objects. Damage to timing light can result.

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Handle the inductive pickup with care. Dropping or sharp blows can damage the ferrite cores. Occasionally inspect the inductive pickup for dirt or other foreign matter buildup on the ferrite cores. Clean with CRC Lectra - Motive 05018 Cleaner or equivalent. Spray surface with plastic tube tip 1" away. Dry with air hose, keeping nozzle at least 6" away.

3. Always refer to applicable manufacturer's test procedures and specifications before testing vehicle. Procedures and specifications may vary from vehicle to vehicle, even if they are of the same manufacturer, year, vehicle model, engine, etc. If a vehicle's timing procedure and specification are not readily available on 3

MT2261A Computerized Tach/Advance Timing Light a Vehicle Emission Control Label, refer to a reliable service manual. Locating this information in a manual will require some or all of the following data: year of manufacture, vehicle indentification number (VIN), engine displacement, type of transmission, and whether it is equipped for Federal or California emission standards. NOTE: Some vehicles that are equipped with compllterized engine control systems may not have a timing procedure or specifications and manufacturer may just state "NONADJUSTABLE". 4. For accurate test results, engine should be at normal operating temperature. Engine may be considered at normal operating temperatyre when upper radiator hose is hot. 5. If dwell is adjustable (distributor points) it should be checked and adjusted to specification prior to timing checks or adjustments. 6. When checking timing on engines with low or unstable speeds, timing marks may fluctuate. This may also occur at higher engine speeds (above 1930 RPM), but is more evident on engines running poorly, idling slow, equipped with light weight flywheels, and those built for racing applications. The fluctuation can be eliminated by entering 1° or 2° of timing light advance. Add this 1° or 2° at the timing mark for actual timing reading. 7. The MT2261A is internally shielded to help eliminate EMI (electromagnetic interference, which includes RFI, radio frequency interference) produced by alternators, battery cables, electric motors, spark plug wires, etc. However, it may be necessary to move the timing light andlor inductive pickup a short distance away from sources of EMI if the display reading or light functions improperly. 8. Solid core and some special application aftermarket spark plug wires can cause improper operation of the timing light. If engine is equipped with either of these types of spark plug wires, replace #1 cylinder's wire with a standard TVRS (television radio suppression) spark plug wire for the test 9. If EMI or RFI causes the timing light's display to "lockup" or show unrealistic data, it may be necessary to press II (Reset) after eliminating the cause of the problem. 10. A bad spark plug wire can cause intermittent or otherwise improper timing light operation. If a plug wire is suspected, either replace the wire or connect the inductive pickup to the plug wire of the companion cylinder' - the cylinder that fires one revolution (360°) from the specified timing cylinder. Determine the companion cylinder by lining up the first half of the firing order over the second half. • Uneven firing engines, such as some GM V-6's with splayed crankshafts, have no companion cylinders. 4

Firing order 1-6-5-4-3-2

1ST half 1-6-5 2ND half 4-3-2

Companion Cylinders 1 &4, 6&3, 5 &2

Most engines are specified to be timed using #1 cylinder, exceptions include: International Harvester V-8 engines which use #8 cylinder, and some GM 4 cylinder engines which are timed by an "averaging method" using 111 and 114 cylinders or all cylinders (coil wire method). 11. For accurate test results the timing marks and reference indicator should be clean and legible. To avoid parallax (an optical illusion that makes an object appear displaced when viewed from an angle), the light should be aimed along an imaginary direct line from the operator's eye through the timing marks to the shaft of the rotating pulley or harmonic balancer, flywheel, etc. (See Figure 1 below). NO

YES

~~~~_ _ _ _ _

NO

Figure 1 12. If the test vehicle's engine is equipped with a receptacle for magnetic probe timing, do not use the receptacle (probe holder) for timing with a timing light. 13. To maintain the appearance of the timing light, periodically clean with a soft damp cloth. To remove grease, use a mild detergent. Do not use cleaning agents such as acetone, benzene, carbon tetrachloride, toluene, etc. Spills such as gasoline, battery acid, brake fluid, penetrating oil, cleaning solvents, etc. should be cleaned immediately.

Ignition Timing Correct ignition timing starts combustion at the proper point in the compression stroke regardless of engine speed and load. Since the amount of time required to burn the fuel mixture (combustion time) remains constant at all engine speeds, ignition must occur earlier in the compression stroke as engine speed increases so that combustion is completed at the proper point in the power stroke. Poor performance and fuel enconomy, high exhaust emission levels, overheating and engine damage can result from improper ignition timing. The MT2261 A stroboscopic timing light is designed for testing initial (base) ignition timing and timing advance operation. The light is connected to the spark plug wire for cylinder 111 (usually). The signals from the inductive pickup

MT2261A Computerized Tach/Advance Timing Light are used to synchronize the flashing of the light with the speed of the engine, so that when the light is aimed at the timing indicator the rotating timing mark appears stationary. The timing reading, or alignment of the timing marks, should agree with the engine's timing specification.

Initial TIming Before base timing can be tested certain preliminary procedures are required. On older vehicles equipped with breaker point ignition systems this involves only that the idle speed be low en9ugh or at a specific RPM and/or that the vacuum advance/retard is disabled. Electronic ignition and computer equipped vehicles have preliminary timing procedures that vary by manufacturer, model, engine, fuel system, pollution control devices, types of electronic and vacuum sensors and acutators, etc. The variations in timing procedures and specifications are too great to be covered in this timing light instruction manual. If you are not sure of this information, always refer to the Vehicle Emission Control Label or a reliable service manual for preliminary timing procedures and specifications.

Initial Timing Using #1 Cylinder 1. Consult Vehicle Emission Control Label, manufacturer's shop manual or a reliable service manual, such as Mitchell or Motor, for timing procedure, specification, and location of calibrated timing indicator and timing mark. Observe all cautions and warnings. 2. Unless otherwise instructed by manufacturer, place transmission selector in park (automatic transmission) or neutral (manual transmission), apply parking brake and block drive wheels. 3. Connect the timing light power leads to a 12 volt battery-first red lead to positive terminal and then black to good vehicle ground. Then place inductive pickup over #1 spark plug wire. Jaws must be firmly seated with the locking button in the lock position.

When power leads are connected the light flashes momentarily and the display will read "2261 ". Then a continuous spelling of "Snap-on" will be displayed; if not, press / / (Reset). 4. After making sure that timing light lead wires are clear of moving or hot engine parts, start the engine.

When engine is started the light will begin flashing and the display will read "0" (zero degrees).

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Press @.r, (Tach/Advance) key for tach function and check engine speed against specification. Adjust RPM as required.

6. [email protected],(Tach/Advance)keyfortimingfunction,aim light towards timing indicator and check ignition timing against manufacturer's specification as follows:

Read timing directly from vehicle's timing indicator with "0" displayed. or Position timing mark to IDC (0°) on timing indicator using .=:::±J (Increase) and ~ (Decrease) keys. Then read timing from LED DISPLAY.

NOTE: When checking or setting timing on engines With ATDC timing, readings must be read directly from

the vehicle's calibrated timing indicator with the timing light display set at "0". Engine's calibrated indicator and timing mark should be clean and you should be familiar with indicator [know position of TDC (0°) and timing degree increments). 7. Adjust timing, if necessary, per manufacturer's procedure and specification. 8. Press

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(Flash) to turn off light.

9. Stop engine and restore vehicle to normal operating condition (engine idle speed, vacuum lines, electrical connections, etc.)

Initial Timing Using"Averaging Method" ofTiming The manufacturers of some engines require that timing readings be taken from the #1 cylinder and its companion cylinder. The two timing readings are totaled and then divided by two to calculate average timing. This average reading is compared to the specification. Timing adjustments to set the initial timing to specification are made with the inductive pickup connected at #1 cylinder.

Example: Cylinder #1 reading is 4° BTDC and companion cylinder reads SO BTDC 4°+So= 12° 12° ... 2 =6°

If the timing specification is 8° BTDC, the adjustment is to advance timing on #1 cylinder 2° (6° average reading is 2° less than SO specification).

Initial Timing Using Coil Wire CAUTION: Use the coil wire method of "average" ;j\ timing only when specified by the . Ll..:) manufacturer. It is intended for initial timing only. Move the inductive pickup to #1 cylinder or its companion cylinder for advance timing. If the coil wire has a plastic cover, slide the cover back to gain access to the wire. Put the cover back in place at the end of the procedure. A timing procedure that requires the initial timing reading to be monitored and set using the coil wire on 4 cylinder engines is specified by some manufacturers. These engines are equipped with two timing notches. The second notch is located 180° from the timing notch for #1 cylinder. With the inductive pickup placed over the coil wire, the light flashes for each cylinder firing. Because the timing light flashes more frequently and there are two timing notches, an image is seen of many notches wavering across a section (between the arrows in the illustration). Use the midpoint of the notches when reading or adjusting ignition timing.

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MT2261A Computerized Tach/Advance Timing light Testing Tip The MT2261 A calculates engine speed from the signal it receives from the inductive pickup. With the inductive pickup connected over the coil wire, the rpm and digital timing readings will be incorrect.

5. Compare digital display reading to advance specification. 6. Repeat steps 2 thru 5 as required at specified centrifugal advance test speeds.

Vacuum Advance

Advance/Retard Timing Controls

A vacuum pump equipped with a vacuum gauge is required for

Centrifugal advance, vacuum advance, vacuum retard, electronic advance, electronic retard, and electronic advance/retard are some of the various timing controls manufacturers equip their engines with to ensure that ignition occurs at the proper point in the compression stroke. These controls may be used individually or in combination. Some common combinations include:

testing vacuum advance system operation.

Vacuum advance and centrifugal advance Vacuum advance, vacuum retard, and

centrifugal advance Vacuum advance, electronic advance, and electronic retard Electronic advance and electronic retard

NOTE: On engines equipped with electronic or vacuum retard controls, proper operation will reflect a retard in timing instead of an advance under certain operating conditions. Accurate advance timing is dependent on proper initial timing. Always make sure that dwell and initial timing are COrrect before testing advance timing. Specific advance timing test procedures and specifications are not presented in this manual. Because of the various types of spark timing controls, combinations of spark timing controls used, and all of the related engine equipment that can affect timing advance that may have to be disconnected, byed, plugged, etc., only general testing procedures are given. Always refer to manufacturer's procedures and specifications if you are not sure of this information.

1. With engine off, disconnect and plug vacuum advance hose and connect vacuum pump to the distributor's vacuum advance port. 2. Start engine. 3. With timing light in the ,iiVij (Advance) mode, press / / (Reset), aim the light at the timing indicator, and note the initial timing reading. 4. Using the vacuum pump, apply the specified amount of vacuum to the vacuum advance unit. 5. While observing the timing mark, press ~ (Increase) to return the timing mark to the initial position. 6. Compare digital display reading to vacuum advance specification. 7. Repeat steps 4 thru 6 as required with the specified amounts of vacuum applied.

Total Advance Depending on the type of ignition control system being tested, total advance is the sum of one of the following: Initial & centrifugal advance Initial. centrifugal &vacuum advance Initial & vacuum advance (including dual diaphram types) Initial, electronic &vacuum advance Initial & electronic advance

Vacuum Retard & Electonic Advance I Retard When testing vacuum retard or electronic retard operation, refer to manufacturer's shop manual for test procedures and specification. On some systems, the timing light's display may have to be set to "0", and the timing is read off of the vehicle's calibrated timing indicator.

Troubleshooting Timing Light PROBLEM

Centrifugal Advance 1. Make sure that initial timing is correct and any preliminary advance timing procedures [hose(s) disconnected and plugged, etc.] are completed. 2. Set engine speed to specified centrifugal advance test RPM. 3. With timing light in @ij (Advance) mode, press / / (Reset) to set timing degrees display to "0". 4. Aim light at timing indicator and press ~ (Increase) to return timing mark to initial position. 6

REFER TO TESTING TIPS #

Light fails to operate

2&10

Intermittent operation Erroneous data displayed

2&10 2,7,8,9&10 3,4,5,11 & 12

Improper timing reading Light flashes out of sync (appears as fluctuating timing mark)

2,6&10

MT2261A Computerized Tach/Advance Timing light

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The OWNER WARRANTY REGISTRATION CARD is applicable only if purchased in the U.s.A. If purchased outside the U.S.A., discard REGISTRATION card.

S'oap-oD. SNAP-ON INCORPORATED Kenosha, WI 53141-141 0 Form ZMT 2261 A DFI

Printed in U.S.A. 3-96