Generac Power Systems 75 Test 33 Check Spark Plugs, Test 34 Check and Adjust Ignition Magnetos

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Section 7

DIAGNOSTIC TESTS

TEST 33 - CHECK SPARK PLUGS

DISCUSSION:

During Test 32, if spark jumped the tester gap, the ignition system must be functioning properly. However, if the engine misses the spark plug itself may be fouled.

PROCEDURE:

Remove spark plugs. Clean with a commercial sol- vent. DO NOT BLAST CLEAN SPARK PLUGS. Replace spark plugs if badly fouled, if ceramic is cracked, or if badly worn or damaged. Set gap to 0.030 inch (0.76mm). Use a Champion RC12YC (or equivalent) replacement spark plug.

Figure 7-35 – Setting Spark Plug Gap

RESULTS:

1.Clean and regap or replace sparks plug as necessary.

2.If spark plugs are good for gasoline models, go to Test 36. For LPG models, go to Test 35.

TEST 34 - CHECK AND ADJUST IGNITION

MAGNETOS

DISCUSSION:

The ignition system used on GTV-760 engines is a solid-state (breakerless) type. The system utilizes a magnet on the engine flywheel to induce a relatively low voltage into an ignition magneto assembly. Ignition magneto internal components increase the voltage and deliver the resulting high voltage across the spark plug gap.

The ignition magneto houses a solid state-circuit board that controls ignition timing. Timing is fixed and spark advance is automatic.

Major components of the ignition system include (a) two ignition magneto assemblies, (b) the spark plugs,

(c)the engine control board and (d) the engine fly- wheel.

Solid-state components encapsulated in the ignition magneto are not accessible and cannot be serviced.

If the magneto is defective, the entire assembly must be replaced. The air gap between the magneto and the flywheel magnet is between 0.012” to 0.015”.

The ignition magneto assembly (Figure 7-36) consists of (a) ignition magneto, (b) spark plug high tension lead and (c) spark plug boot.

Figure 7-36. – Ignition Magneto Assembly

In Test 32, a spark tester was used to check for engine ignition. If sparking or weak spark occurred, one possible cause might be the ignition magneto(s). This test consists of adjusting the air gap between the ignition magneto(s) and the flywheel. The flywheel and flywheel key will also be checked during this test. If no sparking occurs, the ground harness may be at fault.

PROCEDURE:

1.Disconnect the J1 connector from the Engine Control Board. Carefully remove Wire 18A from Pin Location J1-4. Connect the J1 connector back to the engine control board. Repeat Test 32 “Check Ignition Spark”. If the unit now produces spark go to Step 2. If the unit does not produce spark or has weak spark go to Step 4.

2.Do the following:

a.Set a VOM to measure resistance. Connect the positive (+) meter test lead to Wire No.18A (Wire 18A still removed from the J1 connector) Connect the negative (-) meter test lead to a clean frame ground. “Infinity” should be measured, or 0.5 to 1M ohms, depending upon the type of VOM used. If “Continuity” is measured proceed to Step12.

b.Set a VOM to the diode test range. Attach the negative (-) meter test lead to Pin Location J1-4 on the Engine Control Board. (Wire 18A still removed from the J1 connec- tor) Attach the positive (+) meter test lead to frame ground. Set the Start-Stop Switch to START. “Infinity” should be measure dur- ing cranking and running. If the VOM does not have a diode test range, set VOM to measure resistance again. “Infinity” should be measured.

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Contents Diagnostic Repair Manual Replacement Parts SafetyTable of Contents Section Exploded Views / Part Numbers Section Specifications & ChartsElectromagnetic Fields MagnetismElectromagnetic Induction More Sophisticated AC Generator Simple AC GeneratorGenerator Operating Diagram Generator AC Connection System Field BoostLine Breakers 120 Volts only Reconnection for Dual Voltage Output Connection for 120 Volts OnlyStator Assembly Rotor AssemblyBrush Holder Battery Charge ComponentsExcitation Circuit Components GeneralCrankcase Breather Adjustment ProcedureVoltage Regulator DescriptionInstall oil vapor collector and retainer Install BreatherControl Panel Component Identification Check BreatherEffects of Dirt and Moisture Cleaning the GeneratorInsulation Resistance Testers Drying the GeneratorStator Insulation Resistance Brushing and Vacuum CleaningCloth or Compressed AIR Stator SHORT-TO-GROUND TestsTesting Stator Insulation Testing Rotor InsulationTesting Rotor Insulation MegohmmeterVOM MetersMeasuring AC Voltage Measuring DC VoltageMeasuring Current Measuring AC FrequencyMeasuring Resistance Ohms LAW Electrical UnitsAmpere VoltOperational Analysis IntroductionCircuit CONDITION- Rest Circuit CONDITION- Priming Circuit CONDITION- Cranking Choke Heater CH Circuit CONDITION-RUNNINGCircuit CONDITION- Shutdown Sure Switch LOP Circuit CONDITION- Fault ShutdownRecommended Battery BatteryBattery Cables Engine Controller Circuit BoardSTART-STOP Switch Fuel Primer SwitchAMP Fuse Starter Contactor Relay Starter Motor Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Test 1- Check NO-LOAD Voltage Frequency ProcedureTest 2- Check Engine Governor DiscussionTest 3- Test Excitation Circuit Breaker Governor AdjustmentTest 4- Fixed Excitation TEST/ROTOR AMP Draw If continuity was indicated, go to TestRe-connect Wire 11 and Wire 22 to the Voltage Regulator Test 5- Wire ContinuitySet the VOM to measure AC voltage Set a VOM to its Rx1 scaleTest 7 Test Stator DPE Winding Test 6- Check Field BoostIf field boost checks good, replace the Voltage Regulator Across Wires Ohms Test 8- Check Sensing Leads / Power Windings11S 22S Model OhmsTest 10 Check Brushes & Slip Rings Test 9- Check Brush LeadsTance Tests Procedure Test 11- Check Rotor AssemblyTest 12 Check Main Circuit Breaker Replace the Rotor if it fails the testTest 16 Check Battery Charge Rectifier Test 15 Check Battery Charge OutputBattery Charge Rectifier BCR is a full wave rectifier Test 13- Check Load Voltage FrequencyShort to Ground 10. Battery Charge RectifierSet a VOM to read battery voltage 12 VDC Test 19- Test Primer SwitchAlso see Fuel Primer Switch, Test 18 TRY Cranking the Engine13. The LPG Fuel Solenoid FS Test 20- Check Fuel PumpTest 23- Check Power Supply to Circuit Board Test 22- Check Battery & CablesTest 21- Check 7.5 AMP Fuse 17. Start-Stop Switch Test 24 Check START-STOP SwitchSet a VOM to measure DC voltage 12 VDC Test 26- Check Starter Contactor RelayTest 27 Check Starter Motor Test 26A Check Starter ContactorConditions Affecting Starter Motor Performance Tools for Starter Performance Test Checking the PinionMeasuring Current TachometerTest 28- Check Fuel Supply Testing Starter MotorTest Bracket Remove Starter MotorDiscussion LPG Models 28 LP Gas Carburetion DiagramTest 30 Check Wire Test 29 Check Wire 14 Power SupplyBattery voltage is not measured, proceed to Step Crank the engine. The meter should indicate battery voltageTest 32 Check Ignition Spark Test 31 Check Fuel Solenoid Gasoline ModelsConclusion No cylinder is weakest of the two cylinders Cylinder Balance TestTest 33 Check Spark Plugs Test 34 Check and Adjust Ignition Magnetos37. Setting Ignition Magneto Armature Air Gap Adjusting Valve Clearance Test 35 Check Valve AdjustmentChecking Flywheel Magnet Flywheel KEYTest 36 Check Carburetion Install Rocker ARM CoverTest 37 Check Choke Solenoid 43. Connector Down Test / Compression Test Adjust the regulated pressure on the gauge to 80 psiRepeat Steps 1 through 8 on remaining cylinder Check CompressionTest 40 Test OIL Temperature Switch Test 39 Check OIL Pressure SwitchIf all steps check GOOD, go to Test Test 42 Check LPG Fuel Solenoid Test 41 Test Choke HeaterShort to Ground 49. Fuel Solenoid ENCLOSURE/PANEL Removal Major DisassemblyStator Removal Rotor RemovalEngine Removal Belt TensioningStarter Removal FLYWHEEL/MAGNETO Removal Page Section Exploded Views / Part Numbers Part NO. QTY Description Enclosure Drawing No E1011-B QTY Description Sheet Metal Drawing No E1012-E Flywheel Assy GT-990 QTY DescriptionControl Panel Drawing No E1013-A Switch Spdt ON-MOM-ON Wire ASM GRD STD ConnSwitch 6A Spdt Not Shown PANEL, TOP ControlTwin Engine Drawing No E1014-B ASSEMBLY, Breather ASSEMBLY, Crankcase RVASSEMBLY, Head #1 ASSEMBLY, OIL Fill CAPLP Regulator Drawing No E1530 Washer Flat M4 CASTING, Twin Regulator HousingSOLENOID, Twin Regulator SPRING-SOLENOID PlungerSpecifications & Charts Nominal Resistances of Generator Windings AT 68F Generator SpecificationsEngine Speeds and Voltage Specifications Page Electrical Data Electrical Data PO BOX 297 WHITEWATER, WI

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