Generac Power Systems 940, 941 WHY VARIABLE SPEED CONTROL?

Section 1.1

GENERATOR FUNDAMENTALS

3. When the generator circuit breaker is turned to the “ON” position,

AC voltage is delivered to the Full Bridge Rectifier. The AC volt-

age is rectified to DC and thus becomes DC Link voltage.

4. AC voltage from the stator PS1/PS2 is delivered to the inverter.

This is used as the power supply for the inverter circuit board.

5. AC voltage from the stator TIM1/TIM2 is delivered to the system

controller. This is used for engine speed sensing.

6. The system controller sends signals to the inverter for inverter

operation.

7. The system controller senses load voltage and signals stepper

motor operation to achieve required engine speed for correct

voltage output.

WHY VARIABLE SPEED CONTROL?

Most electrical loads will operate satisfactorily only

within a relatively small voltage band. In order to pro-

vide useful voltage at larger load currents, it is neces-

sary to increase engine speed.

In conventional AC generators, some form of voltage

regulation is needed to provide correct voltage in the

full range of load current. This is often accomplished

by regulating excitation current to the Rotor (field)

which then regulates the strength of the Rotor's mag-

netic field. The voltage induced into the Stator wind-

ings is proportional to the strength of the Rotor's mag-

netic field.

The Impact Plus computer controlled generator uses

a Rotor having a fixed and permanent magnetic field.

The strength of this magnetic field is fixed and cannot

be regulated.

The output voltage on Impact Plus computer con-

trolled generators tends to droop with increasing elec-

trical loads. The SYSTEM CONTROLLER maintains

a constant AC output voltage by increasing engine

and Rotor speed as the load current increases, to off-

set this inherent voltage droop.

Page 1.1-5

Contents

Main SAFETY NOTICE TO USERS OF THIS MANUAL REPLACEMENT PARTS Page Page Page Page MAGNETISM Figure 1. Magnetic Lines of Force ELECTROMAGNETIC FIELDS Figure 2. The Right Hand Rule ELECTROMAGNETIC INDUCTION ALTERNATING CURRENT Figure 4. Operation of a Simple Generator ELECTRICAL UNITS Figure 5. Alternating Current Sine Wave Figure 6. Electrical Units OHM'S LAW VOLTS = AMPERES x OHMS Figure 7. AMPERES = VOLTS OHMS OHMS = VOLTS AMPERES Figure 9. Capacitive Reactance Figure 10. Block Diagram of the Impact 36 Plus System WHY VARIABLE SPEED CONTROL? Page Section 1.2 MAJOR GENERATOR COMPONENTS UPPER FAN HOUSING UPPER COOLING FAN PERMANENT MAGNET ROTOR Section 1.2 MAJOR GENERATOR COMPONENTS ROTOR HUB STATOR RETAINING RING STATOR ASSEMBLY STATOR ADAPTER Page Page Section 1.3 OPERATIONALANALYSIS OPERATIONAL DESCRIPTION Figure 1. Block Diagram- A Generator System Section 1.3 OPERATIONALANALYSIS OPERATIONAL DESCRIPTION (CONTINUED) DIRT AND MOISTURE INSULATION RESISTANCE TESTERS Figure 1. One Kind of Hi-Pot Tester STATOR LEADS Figure 2. Stator Leads TEST ALL STATOR WINDINGS TO GROUND TEST FOR SHORTS BETWEEN WINDINGS RESULTS OF TESTS CLEANING THE GENERATOR Figure 3. Schematic- Stator Windings DRYING THE GENERATOR Page STATOR ASSEMBLY Figure 1. Stator Leads STATOR ASSEMBLY (CONTINUED) Figure 2. Schematic- Stator Windings TESTING THE BATTERY CHARGE CIRCUIT Figure 3. Battery Charge Windings and Rectifier Figure 4. Battery Charge Circuit Page Section 1.6 CONTROL PANEL CONSTRUCTION Figure 1. Exploded View of Control Panel COMPONENTS Page 1.6-1 Page Impact Plus Generator Page Page Page PARTS LIST FOR SHEET METAL (GASOLINE UNITS) Page Page Page 4-CYCLE ENGINE THEORY Figure 1. Intake Stroke Figure 2. Compression Stroke Figure 3. Power Stroke Figure 4. Exhaust Stroke RECOMMENDED FUELS NOTE: DO NOT USE GASOLINE CONTAINING METHANOL. NOTE: DO NOT MIX OIL WITH THE GASOLINE. RECOMMENDED ENGINE OIL STORAGE INSTRUCTIONS THE UNIT IS NOW READY FOR SERVICE. ENGINE TUNE-UP NOTE 2:- Use a Champion RC12YC (or equivalent) spark plug with gap set to 0.030 inch (0.76mm). EXPLODED VIEW OF ENGINE LONG BLOCK NOTE 1:- Item 36 Includes valve seats and guides. VALVE TRAIN COMPONENTS VALVE COMPONENTS REMOVAL Figure 4. Cylinder Head Removal Figure 5. Removal of Valve Spring VALVE SERVICE Figure 7. Valve Seat VALVE COMPONENTS INSTALLATION VALVE COMPONENTS INSTALLATION (CONTINUED) ADJUSTING VALVE CLEARANCE Figure 16. Adjusting Valve Clearance Figure 17. Tightening Pivot Ball Jam Nut Figure 18. Rocker Arm Cover Installation ROCKER ARM COVER INSTALLATION Page OVERSIZE PISTON & RINGS PRIOR TO REMOVAL REMOVAL PISTON Figure 4. Piston Minor Diameter PISTON RINGS Figure 7. Ring Locations in Piston Grooves Figure 8. Ring End Gap CONNECTING ROD Figure 9. Connecting Rod ASSEMBLY AND INSTALLATION Figure 10. Match Marks on Rod and Cap CYLINDER SERVICE CRANKCASE COVER REMOVAL Figure 1. Crankcase Cover Removal CRANKSHAFT REMOVAL CAMSHAFT REMOVAL Figure 2. Camshaft Removal CAMSHAFT INSPECTION Figure 4. Points to Check on Camshaft CRANKSHAFT INSPECTION Figure 5. Points to Check on Crankshaft Figure 7. Bearing Bore in Crankcase Cover COMPRESSION RELEASE MECHANISM Figure 7. Compression Release Mechanism on Camshaft Figure 8. Measuring Compression Release Lift INSTALLING THE CRANKSHAFT INSTALLING THE CAMSHAFT Page Page Page Section 3.1 RECOMMENDED FUEL Figure 1. Sharing a Fuel Supply Tank EVAPORATION CONTROL SYSTEMS Page Section 3.2 AIR CLEANER AND INTAKE AIR CLEANER Figure 1. Engine Air Cleaner AIR INTAKE Figure 2. Air Intake Components Page Section 3.3 FUEL FILTER AND FUEL PUMP FUEL FILTER Figure 2. Electric Fuel Pump Figure 1. Fuel Filter (Typical) FUEL PUMP Page GENERAL INFORMATION Figure 1. Carburetor CARBURETOR OPERATION Figure 2. Carburetor Sectional View CARBURETOR DISASSEMBLY CLEANING AND INSPECTION Figure 3. Carburetor Exploded View ADJUSTMENT ENGINE SPEED THROTTLE LINKAGE ADJUSTMENT Figure 4. Set Gap Between Stop Tab and Stop Block Figure 5. Adjusting Throttle Linkage Page Section 3.5 AUTOMATIC CHOKE Figure 1. Choke Solenoid Parts OPERATION OPERATIONAL CHECK AND ADJUSTMENT Figure 2. Choke Adjustment Page Section 3.6 SPEED CONTROL SYSTEM A6060 CIRCUIT BOARD Figure 1. Speed Control System STEPPER MOTOR PROBLEMS Section 3.6 SPEED CONTROL SYSTEM TESTING THE STEPPER MOTOR Figure 2. The Stepper Motor Connector Figure 3. The Stepper Motor Page Page GENERAL INFORMATION ADVANTAGES OF GASEOUS FUELS FUEL SYSTEM COMPONENTS VAPOR WITHDRAWAL IMPORTANT CONSIDERATIONS IMPORTANT CONSIDERATIONS (CONTINUED) FUEL SUPPLY LINES EXCESS FLOW VALVE GASEOUS CARBURETION Figure 2. Gas Carburetion Diagram LEAKAGE TESTING Page Section 4.2 SHUTOFF VALVE AND REGULATOR Figure 1. Shutoff Valve & Regulator ADJUSTMENTS THE LP GAS REGULATOR Figure 2. LP Gas Regulator Section 4.2 SHUTOFF VALVE AND REGULATOR RESULTS OF TEST: Figure 3. Fuel Lockoff Solenoid Page Page Page Page INTRODUCTION TO OIL SYSTEM OIL FLOW Figure 1. Oil System Diagram OIL PICKUP SCREEN OIL PUMP OIL PUMP (CONTINUED) Figure 3. Oil Pump Check Points Figure 4. Crankshaft Oil Seals CRANKSHAFT OIL SEALS PRESSURE RELIEF VALVE OIL SUMP OIL FILTER SUPPORT Figure 7. Oil Filter Support Page Section 5.2 ENGINE COOLING SYSTEM GENERATOR AIR FLOW COOLING AIR INLET OPENINGS Section 5.2 ENGINE COOLING SYSTEM Figure 3 Suspended Mount Inlet Door Figure 5 Air Inlet in Vehicle Skirt Figure 4. Ductwork COMPENSATING FOR RESTRICTIONS Page Page Section 6.1 ENGINE DC CONTROL SYSTEM Figure 1. Schematic- Engine DC Control System HOW IT WORKS NOTE: Also see Section 3.5, "AUTOMATIC CHOKE" and Section 6.2, "A6060 CIRCUIT BOARD". Section 6.2 A6060 CIRCUIT BOARD Figure 1. A6060 Circuit Board CIRCUIT BOARD CONNECTIONS Figure 2. Receptacle J2 NOTE 1: - See "SHUTDOWN FEATURES In Section 6.5 (Page 6.5-1). Section 6.2 A6060 CIRCUIT BOARD CIRCUIT BOARD CONNECTIONS (CONTINUED) Figure 1. Schematic - Cranking Circuit BATTERY BATTERY (CONTINUED) START-RUN-STOP SWITCH (SW1) Figure 2. STARTER CONTACTOR Figure 3. Starter Contactor STARTER MOTOR Figure 4. Starter Motor Page IGNITION CAGE ASSEMBLY NOTE: Also refer to "Permanent Magnet Rotor" in Section 1.2 (Page 1.2-1). Figure 1. Ignition Cage Assembly IGNITION SENSOR Figure 2. Ignition Sensor IGNITION MODULE (CONTINUED) Figure 4. Ignition Module Figure 6. Setting park Plug Gap IGNITION COIL Figure 5. Ignition oil Figure 8. Testing for Spark Figure 9. Checking Engine Miss Figure 10. TESTING THE SYSTEM (CONTINUED) Note: Only one spark should be observed upon initial cranking. Figure 12. Testing Ignition Sensor Figure 13. Testing Ignition Coil Figure 14. Ignition Module Section 6.5 SHUTDOWN FEATURES OIL PRESSURE SWITCH Figure 1. Engine Protective Circuit OIL TEMPERATURE SWITCH Figure 2. Engine Protective Devices Section 6.5 SHUTDOWN FEATURES ADDITIONAL SHUTDOWN FEATURES Section 6.6 OPTIONAL REMOTE PANEL REMOTE PANEL CABLES Figure 2. Model 9042 Remote Panel Figure 1. Remote Panel Receptacle Figure 3. Model 9043 Remote Panel Page Page Page Section 7.1 GENERATOR & SPEEDCONTROL SYSTEM TROUBLESHOOTING REFERENCE CHART Page 7.1-1 Page PROBLEM 1- PRIMING FUNCTION DOES NOT WORK Page Page Page Page Page Page Page Page TEST 1- CHECK 7.5 AMP FUSE Figure 1. 7.5 Amp Fuse TEST 2- CHECK POWER TO PRIMER SWITCH Figure 2. Primer Switch TEST 3- CHECK POWER TO FUEL PUMP TEST 4- CHECK BATTERY/BATTERY CIRCUIT TEST 5- TEST FUEL PUMP TEST 6- TEST PRIMER SWITCH TEST 7- CHECK WIRE 14A TO FUEL PUMP TEST 8- CHECK POWER SUPPLY TO STARTER MOTOR TEST 9- CHECK WIRE 56 POWER TO STARTER CONTACTOR Figure 5. Starter Contactor TEST 10- CHECK A6060 CIRCUIT BOARD POWER SUPPLY TEST 11- TEST STARTER CONTACTOR TEST 12- TEST START-STOP SWITCH Figure 7. Start-Stop Switch TEST 13- CHECK FUEL SUPPLY TEST 14- CHECK FUEL FILTER TEST 17- CHECK IGNITION POWER SUPPLY Figure 9. Ignition Module & 4-Tab Connector TEST 18- CHECK IGNITION SENSOR TEST 19- CHECK IGNITION COIL TEST 20- TEST IGNITION MODULE TEST 22-TEST AUTOMATIC CHOKE TEST 23- CHECK CARBURETION TEST 24- CHECK ENGINE TEST 26- TEST OIL PRESSURE SWITCH TEST 27- TEST OIL TEMPERATURE SWITCH TEST 28 - DC LINK VOLTAGE TEST TEST 29 - 9-PIN WIRE HARNESS/ 2-PIN WIRE HARNESS CONTINUITY TEST - TEST 30 9-WIRE HARNESS SIGNALS TEST Note: Cap the DC Link wires with a wire nut for safety. TEST 31 - STATIC TESTS ON INVERTER Figure 11. 9-Pin Connector on Inverter *NTC thermistor; if inverter is hot, resistance may be several kOhm lower. STATOR TESTS TEST 32 - POWER SUPPLY WINDING TEST TEST 33 - TIMING WINDING TEST TEST 34 -STATOR RESISTANCE VALUES TEST 35 - BRIDGE RECTIFIER TEST TEST 36 - AC POWER WINDING TEST AC1/AC2/SL1/SL2 Page Page Page NOMINAL RESISTANCES OF GENERATOR WINDINGS ENGINE SPEEDS AND VOLTAGE SPECIFICATIONS Page Page CRANKSHAFT END PLAY VALVE TRAIN GENERAL SPECIFICATIONS CRANKCASE ASSEMBLY *Later model small frame GN engines have no crankshaft sleeve bearing. CRANKCASE COVER ASSEMBLY CRANKSHAFT CONNECTING ROD ASSEMBLY PISTON PISTON (CONTINUED) *NOTE 1: Measure end gap with ring pushed down in cylinder to depth of 2.75 inches CAMSHAFT ASSEMBLY OIL PUMP *NOTE 2: Measure pump tip clearance on shaft in crankcase cover. OIL PUMP (CONTINUED) COMPRESSION PRESSURE TORQUE SPECIFICATIONS