Generac Power Systems 4451 & 4986 User Manual

www.guardiangenerators.com
PORTABLES
PO BOX 297 • WHITEWATER, WI 53190
www.guardiangenerators.com
P/N OF7713 REV. A Printed in the USA 6.06
MODELS:
4451 & 4986 (12,500 Watt)
4582 & 4987 (15,000 Watt)
4583 (17,500 Watt)
5209 (15,000 Watt)
5308 (17,500 Watt)
ULTRA SOURCE PORTABLE GENERATOR
DIAGNOSTIC
REPAIR MANUAL
0F7713 Cover-rev.qxd 7/5/2006 4:18 PM Page 1

Generac Power Systems 4451 & 4986 Specifications

General

Brand	Generac Power Systems
Model	4451 & 4986
Category	Portable Generator
Language	English

Summary

Section 3: DESCRIPTION & COMPONENTS

ADJUSTMENT PROCEDURE (12.5 AND 15 KW UNITS)

Provides step-by-step instructions for adjusting the voltage regulator on specific models.

ADJUSTMENT PROCEDURE (17.5 KW UNITS)

Details the adjustment process for the voltage regulator on 17.5 kW units.

TESTING STATOR INSULATION

Provides procedures for testing stator winding insulation resistance.

TESTING ROTOR INSULATION

Outlines the steps for testing rotor winding insulation resistance.

STATOR INSULATION RESISTANCE TEST

Details the specific test for stator insulation.

ROTOR INSULATION RESISTANCE TEST

Details the test procedure for rotor insulation resistance.

Section 4: ENGINE DC CONTROL SYSTEM

FAULT SHUTDOWN

Explains how low oil pressure triggers an automatic engine shutdown.

Section 5: TROUBLESHOOTING FLOWCHARTS

If Problem Involves AC Output

Provides a flowchart for diagnosing AC output issues.

Problem 1 - Voltage & Frequency Are Both High or Low

Troubleshooting flowchart for voltage and frequency issues.

Problem 2 - Generator Produces Zero Voltage or Residual Voltage (2-12 VAC)

Flowchart for diagnosing zero or low AC voltage output.

Problem 3 - Excessive Voltage/Frequency Droop When Load is Applied

Troubleshooting flowchart for voltage/frequency drop under load.

Problem 4 - No Battery Charge Output

Flowchart for diagnosing the absence of battery charging output.

Problem 5 - No 10A Battery Charge Output

Troubleshooting flowchart for issues with the 10A battery charge output.

Problem 6 - Engine Will Not Crank

Flowchart for diagnosing why the engine fails to crank.

Problem 7 - Engine Cranks But Will Not Start

Troubleshooting flowchart for an engine that cranks but won't start.

Problem 8 - Engine Starts Hard and Runs Rough

Flowchart for diagnosing hard starting and rough running engine issues.

Problem 9 - Engine Starts Then Shuts Down

Troubleshooting flowchart for an engine that starts and then shuts down.

Problem 10 - 10 Amp Fuse (F1) Blowing

Flowchart for diagnosing a 10 Amp fuse blowing issue.

Problem 11 - Unit Overspeeds

Troubleshooting flowchart for generator overspeed conditions.

Problem 12 - Idle Control “RPM Does Not Decrease”

Flowchart for diagnosing idle RPM not decreasing with no load.

Problem 13 - Idle Control “RPM Does Not Increase When Load Is Applied”

Troubleshooting flowchart for idle RPM not increasing under load.

Problem 14 - Engine “Hunts” / Erratic Idle

Flowchart for diagnosing engine hunting or erratic idle behavior.

Section 6: DIAGNOSTIC TESTS

TEST 1 - CHECK NO-LOAD VOLTAGE AND FREQUENCY

Procedure to check generator voltage and frequency at no load.

TEST 4 - FIXED EXCITATION TEST/ ROTOR AMP DRAW

Tests rotor amp draw and excitation voltage with a jumpered circuit.

TEST 5 - CHECK STEPPER MOTOR CONTROL

Procedure to test the stepper motor and its control system.

TEST 9 - TEST STATOR

Measures resistance of stator windings to identify faults.

TEST 14 - CHECK ROTOR ASSEMBLY

Tests rotor resistance and checks for shorts to ground.

TEST 15 - CHECK LOAD VOLTAGE & FREQUENCY

Checks voltage and frequency stability under load conditions.

TEST 17 - CHECK BATTERY CHARGE OUTPUT

Measures amperage output for the battery charging system.

TEST 18 - CHECK 10 AMP BATTERY CHARGE OUTPUT

Tests the amperage output of the 10 amp battery charging circuit.

TEST 19 - CHECK BATTERY CHARGE RECTIFIER (BCR2)

Tests the battery charge rectifier (BCR2) for proper diode function.

TEST 23 - CHECK VOLTAGE AT STARTER CONTACTOR (SC)

Verifies 12 VDC supply to the starter contactor.

TEST 24 - CHECK STARTER CONTACTOR (SC)

Tests the starter contactor for proper voltage supply.

TEST 25 - CHECK STARTER MOTOR

Identifies conditions affecting starter motor performance.

TESTING STARTER MOTOR

Outlines the procedure for testing starter motor performance.

TEST 26 - TEST STARTER CONTACTOR RELAY (SCR)

Tests the starter contactor relay (SCR) for voltage and resistance.

TEST 27 - CHECK START-RUN-STOP SWITCH (SW1)

Tests the start-run-stop switch for continuity in different positions.

TEST 29 - CHECK IGNITION SPARK

Procedure to test for ignition spark using a spark tester.

TEST 32 - TEST START STOP RELAY (SSR)

Verifies the operation and wiring of the start-stop relay (SSR).

TEST 35 - CHECK AND ADJUST IGNITION MAGNETOS

Procedures for checking and adjusting ignition magneto air gaps.

TEST 37: TEST FUEL SHUTOFF SOLENOID VOLTAGE

Measures voltage supplied to the fuel shutoff solenoid.

TEST 39 - CHECK CARBURETION

Guides on checking carburetor function and diagnosing mixture issues.

TEST 41 - CHECK ENGINE / CYLINDER LEAK DOWN TEST / COMPRESSION TEST

Diagnoses engine internal issues via leak down and compression tests.

TEST 42 - CHECK OIL PRESSURE SWITCH AND WIRE 86

Tests the oil pressure switch and its associated wiring for proper function.

TEST 47 - CHECK FUEL SHUTOFF SOLENOID (FSS)

TEST 52 - CHECK IDLE CONTROL SWITCH (SW2)

Section 9: SPECIFICATIONS & CHARTS

GENERATOR SPECIFICATIONS