SERVICE MANUAL NUMBER 24
FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
General Information
Electrostatic Discharge Damage
Electronic components are often designed to carry very low voltage and are susceptible to
damage caused by electrostatic discharge. It is possible for less than 100 volts of static elec-
tricity to cause damage to some electronic components. By comparison, it takes 4,000 volts
for a person to even feel the effect of a static discharge.
There are several ways for a person to become statically charged. The most common meth-
ods of charging are by friction and by induction. An example of charging by friction is a per-
son sliding across a seat, in which a charge of as much as 25,000 volts can build up. Charg-
ing by induction occurs when a person with well-insulated shoes stands near a highly
charged object and momentarily touches ground. Charges of the same polarity are drained
off, leaving the person highly charged with the opposite polarity. Static charges of either type
can cause damage. Use care when handling and testing electronic components.
Diagnostic Information
The diagnostic charts and functional checks in this manual are designed to locate a faulty
circuit or component through logic based on the process of elimination. The charts are pre-
pared with the requirement that the system functioned correctly at the time of assem-
bly and that there are no multiple failures.
Wiring Harness Service
Marine engine control circuits contain many special design features not found in standard
land vehicle wiring. Environmental protection is used extensively to protect electrical con-
tacts and proper splicing methods must be used.
The proper operation of low amperage input/output circuits depends upon good continuity
between circuit connectors. Before component replacement and/or during normal trouble-
shooting procedures, visually inspect any questionable mating connector. Mating surfaces
should be properly formed, clean and likely to make proper contact. Some typical causes
of connector problems are listed below.
1.
2.
3.
4.
Improperly formed contacts and/or connector housing.
Damaged contacts or housing due to improper engagement.
Corrosion, sealer or other contaminants on the contact mating surfaces.
Incomplete mating of the connector halves during initial assembly or during subsequent
troubleshooting procedures.
5.
6.
7.
Tendency for connectors to come apart due to vibration and/or temperature cycling.
Terminals not fully seated in the connector body.
Inadequate terminal crimps to the wire.
Wire harnesses should be replaced with proper part number harnesses. When signal wires
are spliced into a harness, use the same gauge wire with high temperature insulation only.
With the low current and voltage levels found in the system, it is important that the best pos-
sible bond be made at all wire splices by soldering the splices, as shown in the following
illustrations. Use care when probing a connector or replacing connector terminals. It is pos-
sible to short between opposite terminals. If this happens, certain components can be dam-
aged. Always use jumper wires with the corresponding mating terminals between connec-
tors for circuit checking. NEVER probe through connector seals, wire insulation, secondary
ignition wires, boots, nipples or covers. Microscopic damage or holes will result in eventual
water intrusion, corrosion and/or component or circuit failure.
Index
90-861327
OCTOBER 1999
Page 5D-5
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 305 CID, Mercury MerCruiser 350 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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