Electronic Repair Of 6V3100 Diesel Engine Timing Indicator{0651, 1250} Caterpillar

The following information given is for repair only of the indicator. Basic troubleshooting information for the complete group is given in Special Instruction Form SEHS7742, "Service Information and Use of 6V3100 Diesel Engine Timing Indicator Group".

Operation Of System

The 6V3100 Diesel Engine Timing Indicator Group measures fuel injection timing while the engine is in operation by finding at what degree BTC (before top center) that fuel is injected into number one cylinder. It makes a comparison with TC (top center), and the difference in time between these two points is measured and read out in degrees BTC. The pressure transducer monitors the fuel line pressure and provides an output that is calibrated for a predetermined pressure. When the fuel line pressure reaches this predetermined value of 6895 kPa (1,000 psi), the pressure transducer signals the indicator to start measuring time. The engine continues to rotate to top center, where the TDC transducer (magnetic pickup) outputs a signal corresponding to engine TC. This signal is generated by sensing the location of the static timing pin hole (located in flywheel or timing gear, depending upon the engine model). At this instant, the indicator stops measuring time and gives the number of crankshaft degrees between full injection and top center on the DEG display.

Block Diagram - 6V3100

Circuit Operation

R/MIN Readout

6V2192 Injection Transducer - The 6V2192 has a differential output between connector pins J301-4 and J301-2 (see 6V3100 INDICATOR SCHEMATIC insert). At a fuel line pressure of 6895 kPa (1,000 psi), J301-4 is zero Volts with respect to J301-2. Increasing the pressure causes J301-4 to "crossover" from negative to positive with respect to J301-2. When this happens, the output of IC301B, TP13, goes low.

Alternate Pressure Transducers - Other types of pressure transducers may be used to sense injection if their outputs equal 2.830 Volts at 6895 kPa (1,000 psi). Because J301-2 is adjusted to 2.830 Volts positive with respect to ground (J301-3), any input on J301-4 that crosses through (from negative to positive) 2.830 Volts with respect to J301-3 will also cause the output of IC301B, TP13, to go low.

IC301A is a zero crossing detector. Its output switches (changes state) every time that J301-4 crosses through zero Volts with respect to J301-2. TP13 goes low (-5V) every time the injection pressure in line number one gets to 6985 kPa (1,000 psi) and returns high (+8 V) at the end of each injection pulse. When TP13 goes low, it clocks (triggers) the 23 ms Monostable, IC302A, so its output TP14, goes high. This output serves two purposes.

1) Switches (changes state) the output of DEG Flip-Flop, TP20, high.

2) Input signal for R/Min Limiter.

The R/Min Limiter output, TP16, goes high with TP14 but TP16 amplitude is a precision 5 Volts as determined by REG102. TP16 stays high until 23 ms Monostable IC302A times out. So, TP16 is then a series of constant amplitude, constant duration pulses whose repetition rate is proportional to engine speed. One pulse is generated on TP16 for each fuel pulse.

The R/Min Filter, IC304, is an active low pass filter with a gain of 0.20. It filters the pulses from TP16 into a smooth dc. R/Min Calibrate, R313, provides a calibrated output on TP17 that is read by digital voltmeter DVM1/LCD1, as engine speed in R/Min (revolutions per minute). The injection transducer is the input for the speed or R/Min readout, and the reference for the timing or DEG display.

DEG Readout

When a fuel pulse causes TP14 to go high (see R/Min Readout), it triggers the DEG Flip-Flop output, TP20, high. TP22 then also goes high, and is a precision 5 Volts as determined by REG102. TP22 stays high until the engine reaches top center.

The TDC transducer senses top center of the engine. It outputs a pulse as the static timing pin hole (flywheel or cam gear) passes by. This pulse is first negative going and then positive going. The exact center of this hole is represented by zero Volts when the signal transition goes from negative to positive. A zero crossing detector made up of (two comparators) IC301C detects this zero Volt transition and causes TP18 to go low (-V). This generates a trigger pulse, TP19, that serves two purposes:

1) Resets the 0.5 Sec Degree Lockout Monostable, IC204B. This IC is a retriggerable monostable and is reset by every TDC pulse. If IC204B gets a reset pulse with each engine revolution, it will stay reset and never time out. This reset condition is indicated by the NO TDC SIGNAL lamp being off. The output of IC204B, pin 9, inhibits the DEG Flip-Flop from being set by a fuel pulse if there is no associated TDC pulse. (A fuel pulse without a TDC pulse will cause the DEG display to go off scale and read approximately 60 degrees.)

2) It also clocks the DEG Flip-Flop output, T20, low. This is now the end of the pulse that represents timing.

The pulse train at TP22, output of the DEG Limiter, is of constant amplitude but varying pulse width-varying proportional to timing for a given engine speed. Engine speed and pulse repetition rate are proportional but the duty cycle of this pulse train (ratio of "on time" to "off time") varies proportionally to engine timing and contains the actual timing data.

The DEG Filter, IC305, is an active low pass filter with a gain of 2.66. It filters the pulses from TP22 into a smooth dc. DEG Calibrate, R328, provides a calibrated output on TP23 that is read by digital voltmeter DVM2/LCD2 as engine/fuel system timing in degrees before top center.

Power Supply

Switch S101 selects polarity of input that is correct for power cable hookup. Diode D101 prevents operation from backward power hookup. Series pass transistor Q101 regulates output to a nominal 12 Vdc. Output will be less than 12 Volts if input is below 14 Vdc.

Three terminal regulator, REG101, must be adjusted to 8.00 ± .01 Volts and supplies regulated power to logic and to the injection transducer. Precision 5 Volt regulator, REG102, provides a reference voltage for the R/Min Limiter, DEG Limiter, the two voltmeter IC's, DVM1 and DVM2 and the Injection Switchpoint bias voltage.

The -5V Converter uses IC101 as a chopper (approximately 20 kHz) to convert 12 Vdc to ac. A voltage doubler then provides sufficient dc for D106 to regulate TP7 to approximately -5 Volts.

6V2197 TDC MAGNETIC TRANSDUCER SCHEMATIC

6V2192 INJECTION TRANSDUCER SCHEMATIC

PC BOARD LAYOUT FOR UNITS BUILT BEFORE APPROXIMATELY S/N 1950 NOTE DATE ON PC BOARD

PC BOARD LAYOUT FOR UNITS BUILT AFTER APPROXIMATELY S/N 1950 NOTE DATE ON PC BOARD

Power Supply - Parts List

Main Circuit - Parts List

Displays - Parts List

Calibrator - Parts List

Test Points (Voltages And Waveforms)

dc Voltages

Conditions:

1. dc input voltage applied to POWER connector as shown.

2. CALIBRATION CHECK/OPERATE switch in the OPERATE position.

3. Neither transducer connected to indicator.

4. TPI is reference for all voltages.

Equipment Required: 6V3030 Digital Multimeter

dc Input Voltages

Waveforms

Conditions:

1. dc power input voltage of 25 ± 1 Volts.

2. CALIBRATION CHECK/OPERATE switch in the CHECK position (can be held in CHECK position with tape).

3. Neither transducer connected to indicator.

4. TPI is reference for all waveforms.

Equipment Required: dc oscilloscope (dual channel preferred).

Waveform Time Relationships

NOTE: VOLTAGES MAY VARY ± 10%, PULSE DURATIONS BY ± 20% EXCEPT 2.66 ms WHICH IS BASED ON A 12.000 kHz OSCILLATOR FREQ. (1C202). SIGNAL SOURCE IS INTERNAL CALIBRATOR. ALL TEST POINTS REFERENCED TO TP1.

Waveform Time Relationships (enlarged scale)

NOTE: NOTE: VOLTAGES MAY VARY ± 10%, PULSE DURATIONS BY ± 20% EXCEPT 83.3 ?s AND 2.66 ms WHICH ARE EXACT BASED ON A 12.000 kHZ OSCILLATOR. (1C202) SIGNAL SOURCE IS INTERNAL CALIBRATOR. ALL TEST POINTS REFERENCED TO TP1.

Disassembly Procedure

1 Remove six screws (1) from front panel (2), and remove panel (2) from case (3). Remove four screws (4) from the PC board, and also remove the locknuts from the two front panel switches (5) and (6). Carefully lift front panel (2) from PC (printed circuit) board (7).

Calibration Procedure

To make sure the 6V3100 Timing Indicator Group (1) has good accuracy, check its calibration at a minimum of every six months. Also, the timing indicator will need calibration if:

A. It does not show 2000 ± 30 R/MIN at (A) and 32.0 ± .2 DEG at (B), when the CALIBRATION CHECK-OPERATE Switch (C) is in the CALIBRATION CHECK position.

NOTE: With no input signal at (D) or (E), the reading at R/MIN location (A) must show three zeros (000). If four zeros (0000) show, it is an indication of a possible need for calibration of the unit. This error only is not reason enough to do a complete calibration procedure. It is also not necessary to do a complete calibration procedure if the reading at the DEG location (B) has a decimal point as shown, (00.0) in addition to the three zeros.

B. Reading is different than (000) at either location (A) or (B).

All calibrations can be done with the use of a small screwdriver, a frequency counter and a 6V3030 DMM (digital multimeter). If a frequency counter and a digital multimeter are not available, a 5P9698 Calibrator can be used as a replacement, but it is probable that the interval will be shorter until calibration is again necessary.

(1) Remove six screws (2), along the edge, then lift panel (3) from its case.

(2) Put power to the 6V3100 Timing Indicator for two minutes or more to get it warm, then use one of the procedures that follow, according to the calibration tools to be used.

Calibration Using a Frequency Counter

(1) Connect a frequency counter from TP10 to TP1 (ground).

(2) Adjust R204 (OSC. FREQ. ADJ.) so the counter reads 12,000 ± 5 Hz. Disconnect the frequency counter.

(3) Connect a 6V3030 DMM (or equivalent multimeter) from TP17 to TP1 (ground). Adjust the DMM to the DCV-200 m scale.

(4) Adjust R312 (R/MIN BALANCE) so the DMM reads + 0.1 mV.

NOTE: If a DMM is not available, turn R312 CCW until the fourth "zero" shows (normally only three zeros) at R/MIN, location (A). Then turn R312, one to one and one-fourth turns CW.

(5) Connect the multimeter from TP23 to TP1, and set it to the DCV-200 m scale.

(6) Adjust R327 (DEG. Balance) so the DMM reads + 0.1 mV. Disconnect the DMM.

NOTE: If a DMM is not available, turn R327 CCW until the decimal point shows at DEG, location (B), then turn R327, one-half turn CW.

(7) Hold the CALIBRATION CHECK-OPERATE switch in the CALIBRATION CHECK position.

(8) After there is stability in the necessary readings at locations (A) and (B), adjust R313 (R/MIN CALIBRATE) so the reading at location (A) is exactly 2000. To do this, turn R313 (CW and then CCW) to change the reading at location (A) to 1990, and then 2010. Now, adjust R313 so it reads exactly 2000 at location (A).

(9) Adjust R328 (DEG CALIBRATE) so the reading at location (B) is 32.0. To do this, turn R328 (CW and then CCW) to change the reading at location (B), then adjust it to read exactly 32.0.

(10) Release the CALIBRATION CHECK-OPERATE switch.

Calibration Using a 5P9698 Calibrator

(1) Connect a 6V3030 DMM (or similar tool) from TP17 to TP1 (ground), and set it to the DCV-200m scale.

(2) Adjust R312 (R/MIN BALANCE) so the DMM reads + 0.1 mV.

NOTE: If a DMM is not available, turn R312 CW until the fourth "zero" appears (normally only three zeros) at location (A), then turn R312, one to one and one-fourth turns CW.

(3) Connect a 6V3030 DMM (or similar tool) from TP23 to TP1 and set it to the DCV-200m scale.

(4) Adjust R327 (DEG. BALANCE) so the DMM reads + 0.1 mV.

NOTE: If a DMM is not available, turn R327 CCW until the decimal point shows at DEG, location (B), then turn R327 one-half turn CW. Disconnect the DMM.

(5) Use the large adapter plug to connect cable (1) of the 5P9698 Calibrator (2) to the R/MIN CAL. INPUT jack of 6V3100 Timing Indicator (3) as shown. Adjust the calibrator to 25 Hz.

(6) Adjust R313 (R/MIN CALIBRATE) so the reading at location (A) is exactly 3000. To do this, turn R313 CW and then CCW, so the reading at location (A) will be 2990 and then 3010, then adjust it to exactly 3000.

(7) Disconnect calibrator (2) and turn it OFF.

(8) Hold the CALIBRATE CHECK-OPERATE switch in the CALIBRATION CHECK position.

(9) Adjust R204 (OSC. FREQ. ADJ.) so the reading at location (A) is exactly 2000. To do this, turn R204 CW and then CCW so the reading at location (A) will be 1990, and then 2010, then adjust it to exactly 2000.

(10) Adjust R328 (DEG CALIBRATE) so the reading at location (B) is 32.0. To do this, turn R328 (CW and then CCW) to change the reading at location (B), then adjust it to read exactly 32.0.

(11) Release the CALIBRATION CHECK-OPERATE SWITCH.

Power Supply Adjustments

(1) Connect a 6V3030 DMM (or similar tool) from TP3 to TP1 (ground) and set it to the DCV20 scale. Adjust R104 (+ 8 V ADJ) until the DMM reads 8.00 ± .01 Volts.

(2) To adjust the 2.830 Volts on TP4, (INJECTION SWITCH POINT ADJUST), use the following procedure. (The 6V3030 DMM cannot measure this voltage as 2.830 but would instead show 2.83.)

a) Connect a 6V3030 DMM from TP6 to TP1 (ground) and set it to the DCV2 scale. Measure this exact voltage and make a note of it. It should be + 1.500 ± .010 Vdc.

b) Subtract the above "1.500" voltage from 2.830 Volts (Example: 2.830-1.502 = 1.328 Volts).

c) Connect a 6V3030 DMM from TP4 (red lead) to TP6 (black lead). Adjust R105 (INJECTION SWITCH POINT ADJUST - shown as "INJECTION SWITCH PT" on PC board) until the DMM reads the exact voltage as determined in step (b) above.

Parts And Repair Service

For warranty or repair work for the 6V3100 Diesel Timing Indicator (indicator only) send the indicator to:

Telephone: (414) 656-5499

Always give:

1) Description of the type of problem.

2) Where to send indicator after repair.

3) Person the indicator should be sent to.

4) Billing address, if different than shipping address.

NOTE: Any 6V2192 Injection Transducer that is not within the specifications given in step 6 of the topic, Check 6V2192 Injection Transducer, in Form SEHS7742, should be sent to Setra Systems, Inc. for repair. The address is given on the last page of Form SEHS7742.