TROUBLESHOOTING
SERVICE MANUAL NUMBER 24
High Speed Glazing
Insulator has yellowish, varnish-like color, indicating that temperatures suddenly have risen,
usually during hard, fast acceleration under heavy load. Normal deposits do not get a
chance to blow off. Instead, they melt and form a conductive coating. Replace spark plugs.
If condition recurs, use colder heat range plug and service plugs more frequently.
72421
Scavenger Deposits
Powdery white or yellow deposits are built up on shell, insulator and electrodes. This is nor-
mal appearance with certain branded fuels. Accumulation on ground electrodes and shell
areas may be unusually heavy, but may be easily chipped off. Plugs can be serviced (clean,
file and regap) and reinstalled.
72422
Pre-Ignition Damage
Pre-ignition damage is caused by excessive high temperatures. Center electrode melts
first, followed by ground electrode. Normally, insulators are white but may be dirty if plug has
been misfiring. Check for correct plug heat range, advanced ignition timing, lean fuel mix-
ture, incorrect fuel used, malfunctioning cooling system, leaking intake manifold or lack of
lubrication. Replace spark plugs.
72422
Index
Page 1C-4
90-861327--1 OCTOBER 1999
| 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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