Introduction - Briggs & Stratton VANGUARD M490000 Repair Manual

Verify Customer Complaint
Verify customer complaint and then move to the
Diagnostic Table that best describes the problem.
• Engine does not crank.
• Engine cranks but does not start.
• Engine exhibits hard start symptoms.
• Engine power output low.
• Engine hunts and surges.
Perform Visual Check
4
Each Diagnostic Table contains an instruction to perform
a careful visual check. This check should always include
the following:
• Verify that ECM grounds and sensor connections are
clean, tight and in their proper location.
• Thoroughly check for any type of vacuum leak or
restriction.
• Look for air leaks at the throttle body mounting and
intake manifold sealing surfaces.
• Inspect ignition wires for cracks, hardness, improper
routing and carbon tracking.
• Inspect wires for kinks, cuts, burns, abraded
insulation, and other damage.
• Look for moisture in primary or secondary ignition
circuit connections.
• Look for salt corrosion on electrical connections and
exposed throttle body linkages.
Check electrical connectors for the following:
• Poor mating of connector halves, or a terminal not
fully seated in the connector body (backed out or
loose).
• Improperly formed or damaged terminals and/or
connectors.
• Improper contact tension of connector pin and socket
terminals in the problem circuit.
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INTRODUCTION

• Poor terminal to wire connection (both core and
insulation crimps).
Intermittents
IMPORTANT: Intermittents may not cause the MIL to
illuminate or set a DTC. DO NOT use the DTC Tables
to diagnose intermittent problems. The fault condition
must be present to locate the problem. Many intermittent
problems are caused by faulty electrical connections or
wiring.
The engine may be operated with a DVOM connected
to the suspect circuit. If an abnormal voltage is observed
when a malfunction occurs, it is a good indication that
there is a fault in the circuit. The Diagnostic Tool also may
be used to help detect intermittents.
Check DTC Memory Loss
Disconnect MAP sensor and idle engine until MIL is
illuminated. DTC P0107 should be set and stored in ECM
memory when the ignition is turned OFF. If it is not, then
the ECM is faulty. After performing this test, be sure to
clear the DTC from memory.
An intermittent MIL with no stored DTC may be caused by
one or more of the following conditions:
• Ignition coil is shorted to ground and arcing is present
at ignition wires or plugs.
• MIL wire to ECM is shorted to ground.
• Poor ECM grounds.
• An electrical system interference caused by a sharp
electrical surge. The problem normally occurs when
the faulty component is operated.
• Secondary ignition components are shorted to
ground, or there is an open in the ignition coil ground.
• Engine components, such as starters, alternators or
relays, are internally shorted to ground.