3500B Direct Fuel Control Modification (Hardware Version II){1250, 1901} Caterpillar

Engine:

3508B (S/N: 2HW1-UP; 3DW1-UP)

3512B (S/N: 1PW1-UP; 4AW1-UP)

3516B DI EUI TA (S/N: 1NW1-UP; 2FW1-UP)

Introduction

This modification is recommended for the following engines: 3508B land and offshore petroleum engines, 3512B land and offshore petroleum engines and 3516B land and offshore petroleum engines. These engines must be equipped with the electronic instrument panel. This modification can be applied only when there is an external 0 to 200 mA engine fuel control signal. These applications include SCR systems.

Description and Function

The engine Electronic Control Module (ECM) normally uses a desired speed signal to set the steady engine speed. This system depends on the engine ECM in order to govern the engine at a steady engine speed. Direct fueling bypasses the governor in the engine ECM. In addition, direct fueling sends a signal directly to the injection portion of the engine ECM.

This modification consists of a control signal filter and a current-to-PWM (Pulse Width Modulated) converter. The converter sends the PWM signal to the engine ECM. This modification allows SCR controlled systems to use an engine actuator signal of 0 to 200 mA. This signal is used to control a 3500B series engine. The modifications to the software within the engine ECM allow this control signal to directly control the virtual rack position of the engine. When the direct fuel control is enabled, the input control current from the SCR control is proportional to the desired fuel. The engine ECM retains basic engine protection functions.

Illustration 1	g00712782

Once the modification is installed, the capabilities of load sharing that are built into the SCR control can be fully utilized. With this modification, it is easy to repower a D399 engine with a 3500B series engine. This modification also makes it possible to parallel a 3500B series engine with a mechanical unit injected (MUI) engine.

The following major components are added during this modification:

• A resistive/inductive input filter

• One control group that is used to convert the 0 to 200 mA signal to a PWM signal

• Software that is flashed into the engine ECM which allows the direct fueling to function

Glossary of Terms

Engine ECM - Electronic control module for 3500B series engines

ECS (Engine Control Switch) - The switch is located on the electronic instrument panel. The switch is considered to be the master control for the engine.

EIP (Electronic Instrument Panel) - The EIP contains the electrical connections that are used for the engine's instrumentation and the engine's controls. This panel is usually mounted on the 3500B series engine. In some applications, the EIP may be mounted in a remote location.

Subpanel for the EIP - The subpanel is a steel plate that is mounted in the back interior of the EIP. This plate supports most of the internal components of the EIP.

Threaded insert - A threaded insert is a nut fastener that compresses during installation. A threaded insert can be installed permanently from one side of the panel.

PWM (Pulse Width Modulation) - The use of PWM is a means of transmitting data. When the ratio of ON TIME to OFF TIME is changed in a square wave signal, data is transmitted. A PWM signal is commonly used for throttle signals and sensor signals.

Electrical converter - The electrical converter converts a zero to 200 mA signal to a specific PWM duty cycle.

SCR (Silicon Controlled Rectifier) - An SCR is a solid state device that can be turned on at a specific point in the AC sine wave. These devices are the main switching elements in SCR systems that are used to control petroleum drilling machinery.

Installation

The following list is a list of common tools that are required:

• various screwdrivers

• wrenches

• crimper

• electric drill

• 1/4 inch drill bit, 3/8 inch drill bit

Rework Procedure

Hardware Installation

1. Ensure that all power has been removed from the engine.

2. Disconnect the wires that are connected to the 9X-9591 Electrical Converter Group . Remove the Electrical Converter Group from the EIP's subpanel.

3. Carefully remove the add-in harness that is used to connect to the 9X-9591 Electrical Converter Group . This harness is not part of the main panel harness. Ensure that all conductors of the harness are removed. The following harness conductors should be removed: the lead that is routed to Connector A, Pin 14 that is located at the bottom of the EIP and the low idle switch. The wires that are connected to the low idle switch are part of the add-in harness. These wires should also be removed.

   Note: When the direct fueling mode is used, the low idle switch should not be installed.

4. Use Illustration 4 in order to mark the mounting hole location for the 180-7359 Control Group and the 174-1433 Inductor . At the locations that are marked for the Control Group, use a 1/4 inch drill bit to drill two holes into the EIP subpanel.

5. Use the 178-7635 Threaded Insert Installation Tool to install two 176-1691 Threaded Inserts . These threaded inserts are used to support the Control Group. To install an insert, thread the insert all the way onto the tool mandrel. Hold the insert tool with a box wrench. Turn the mandrel with another box wrench or a ratchet wrench. Continue to turn the mandrel until the threaded insert is installed.

6. At the location that is marked for the 174-1433 Inductor , use a 3/8 inch drill bit to drill one hole.

7. Use the 179-3571 Threaded Insert Installation Tool to install the 178-1628 Threaded Insert .

8. Locate the 174-1433 Inductor . Mount the inductor in the location that is shown on Illustration 4. The inductor is mounted by using an 8B-2377 Bolt and a 5P-0537 Hard Washer .

   Note: Both the Control Group and the inductor may be mounted with the use of self-tapping screws. When self-tapping screws are used, the screw size and the pilot-hole size are critical.

Note: Step 9 may not be necessary if the Control Group is already assembled.

9. Locate the 180-7359 Control Group components. Install the 180-7384 Resistor in the 115-2542 Plug . Install the plug into the 135-6740 Diode Block . To install the plug into the diode block, push the plug into the receptacle on top of the diode block. Attach the 9X-9616 End Cover to the open side of the 135-6740 Diode Block . Slide a 9X-9675 End Bracket onto the DIN rail. Attach the 135-6740 Diode Block (with the resistor installed) to the DIN rail. Position the diode block next to the end bracket. Slide another end bracket onto the DIN rail. There should be an end bracket on both sides of the diode block. Tighten the end brackets to firmly hold the diode block in place.

10. Locate the two mounting holes for the 180-7359 Control Group. Use two 7S-1197 Screws and two 4B-4863 Washers to install the control group.

11. Install one inductor lead to the resistor terminal that is marked "R1B". If the resistor block is not labelled, "R1B" is the bottom terminal of resistor R1.

12. Place the 180-7357 Harness Assembly in the EIP. Orient the harness so that the ends marked "Cust Conn C 01" and "Cust Conn C 02" are located next to the customer connector. The customer connector is located at the bottom of the EIP. Place the harness conductors ("Conv 12", "Conv 10", etc) close to the installation location of the inductor.

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Illustration 2	g00712716
Orientation of the 175-4998 Current-to-PWM Converter. (1) 175-4998 Current-to-PWM Converter (2) Pins 1,3,4, and 6 (3) Offset Adjust (4) Power OK Lamp (5) Span Adjust

13. Refer to Illustration 2. Position the converter as follows:
    • Pins 1,3,4, and 6 are on the bottom.

    • The adjustment potentiometers are facing left.

    • The "Power OK" indicating lamp is facing left.

14. Place the converter over the location that was previously occupied by the 9X-9591 Electrical Converter Gp (Speed Brick). The new converter will be mounted in this location. The new converter (175-4998) will use a mounting plate (178-1660) and the same mounting holes that were used by the 9X-9591 Electrical Converter Gp . Do not firmly mount the 175-4998 converter at this time.

15. Connect the negative lead of the 0 - 200 mA control signal to pin 3 of the 175-4998 converter. The harness conductor is marked with "Conv 02 Conv 3". Connect the remaining lead of the 50 mH inductor to pin 1 of the 175-4998 converter.

    Note: In order to prevent conductor failure that is caused by wire fatigue, the installation of ferrules is highly recommended.

16. Connect the remaining harness leads to the converter. Ensure that each lead is connected to the correct terminal. The harness conductors are marked with the correct pin number preceded by the abbreviation for converter ("Conv").

17. To mount the 175-4998 converter, use the following items: 178-1660 Mounting Plate, two 4B-4863 Washers and two 7S-1198 Screws . Install the converter between the subpanel and the mounting plate. Tighten the screws just enough to securely hold the plate. Do not overtighten the screws.

18. Connect the harness lead that is labelled "R1A" to the 20 ohm resistor terminal "R1A".

19. Locate the harness lead that is labelled "CONA-14". Insert this connector pin into the rear of pin 14 of bulkhead mounted Connector A.

20. Connect both leads labelled "TB-12" to any open terminal on "TB-12". If open connection points are not available, you may need to add an extra 115-1322 Terminal.

21. Locate the harness leads labelled "CONC-01" and "CONC-02". Install each of these connector pins in the rear of bulkhead mounted Connector C. "CONC-01" is inserted into location 1. "CONC-02" is inserted into location 2.

22. Locate the harness lead that is labelled "TB-4". Connect this lead to any open point on "TB-4".

23. Use cable ties to secure the wires to the existing harness. Leave some slack in the wires close to the converter. This slack will allow adjustment of the converter's potentiometers (if necessary).

24. Check the wiring to ensure that proper connections have been made.

Adjusting the 175-4998 Converter

1. Ensure that power has been removed from the Electronic Instrument Panel.

2. Remove the wire that is connected to pin 1 of the converter.

3. Apply power to the Electronic Instrument Panel.

4. With a digital multimeter equipped with a Duty Cycle Mode, measure the duty cycle of the converter's output. Refer to Table 4. The duty cycle of the converter's output can be measured across pins 10 and 12.
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   Table 4

   TOOLS NEEDED
   Tool	Part Number
   Caterpillar Digital Multimeter	146-4080
   Digital Multimeter with Duty Cycle Mode	N/A

5. Adjust the Offset Potentiometer in order to provide a five percent duty cycle. The Offset Potentiometer is one of two small potentiometers that are located in the top of the converter.

   Note: This control is sensitive to adjustments. Make small corrections and wait a few seconds to observe the response.

6. When the Span potentiometer is adjusted, minor adjustments of the PWM duty cycle occur across the entire range of operation. This control is best adjusted by using a 0 - 200 mA current source. DO NOT EXCEED 230 mA OF CURRENT IN THIS CONTROL CIRCUIT. For a correlation between the control current and the PWM duty cycle, Refer to Table 5.

7. Remove power from the EIP.

8. Reconnect the wire to pin 1 of the converter.

9. Apply a small amount of 9S-3263 Thread Lock Compound to the 7S-1198 Screws . Torque the two 7S-1198 Screws to 1.7 ± 0.25 N·m (15.05 ± 2.213 lb in).

10. Start the engine and operate the engine.

    Note: THE ENGINE SPEED IS NOW CONTROLLED BY THE 0 - 200 mA SIGNAL.

Maintenance

Theory of Operation

Coil "L1" and resistor "R1" replace the standard load for the actuator. The control signal for engine speed was originally designed to drive this load. These components provide signal filtering and match the impedance of the SCR signal source.

The 0 - 200 mA control signal is converted to a PWM signal in the 175-4998 converter. This signal sets the engine fuel rack. The input circuit of this converter utilizes a thermal overload feature to aid in the protection of the converter. When the potentiometers that are located on the control are used, some span and offset adjustment is possible. The expected conversion of the fuel control hardware is shown in Table 5. The engine ECM uses the signal from the converter to control the duration of injection.

The engine software is modified in order to bypass the speed control of the ADEM II ECM. Prior to operating in the direct fueling mode, direct fueling must be enabled in the configuration screen of Cat ET.

Troubleshooting

Possible Problems

Engine fails to start - The direct fueling software requires a starting rack value. If the control current loop is open, the engine will not start. Ensure that there is starting control current in the 0 - 200 mA control signal loop.

Engine starts and goes to high idle - Use a Caterpillar Digital Multimeter to measure the PWM duty cycle at pin 12 of the 175-4998 Converter. If the duty cycle is too high, measure the input control current with the Digital Multimeter. Compare the duty cycle with the input control current. The correlation must be close to that stated in Table 5.

Engine starts and seems to respond to control changes but will not perform at rated RPM and power - Ensure the engine ECM software is enabled for direct fueling. This is accomplished in the Configuration menu in CAT ET. Both the 180-7384 Resistor and the 174-1433 Coil may be removed from the circuit by temporarily shorting around the component. If the circuit operates normally when either of these components is shorted, replace the component. To verify this action, use a multimeter to perform a component check.

Illustration 3	g00712809

Diagram of the Inductor's Location

Illustration 4	g00712922

Correlation Between Control Current and PWM Duty Cycle

Diagram of the 178-1660 Plate Used for Installing the 175-4998 Converter

Illustration 5	g00713023