Cold Fouling
High Speed Glazing
Dry, black deposits indicate rich fuel mixture or weak
ignition. Clogged flame arrestor, flooding carburetor,
sticky choke or weak ignition components all are
probable causes. If, however, only one or two plugs
in set are fouled, check for sticking valves or bad igni-
tion leads. After correcting cause, service (clean, file
and regap) plugs and reinstall.
Insulator has yellowish, varnish-like color, indicating
that temperatures suddenly have risen, usually dur-
ing hard, fast acceleration under heavy load. Normal
depositsdonotgetachancetoblowoff.Instead,they
melt and form a conductive coating. Replace plugs.
If condition recurs, use colder heat range plug and
service plugs more frequently.
72421
72421
Overheating
Scavenger Deposits
Insulator is dull white or gray and appears blistered.
Electrodes are eroded and there is an absence of de-
posits. Check that correct plug heat range is being
used. Also check for over-advanced ignition timing,
cooling system malfunction, lean fuel/air mixtures,
leaking intake manifold or sticking valves. Replace
spark plugs.
Powdery white or yellow deposits are built up on
shell, insulator and electrodes. This is normal ap-
pearance with certain branded fuels. Accumulation
on ground electrodes and shell areas may be unusu-
ally heavy, but may be easily chipped off. Plugs can
be serviced (clean, file and regap) and reinstalled.
72422
72421
Index
90-823224--2 796
TROUBLESHOOTING - 1C-3
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1993, 1994, 1995, 1996, 1997 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(4 votes, average: 4.5 out of 5)
Marine readers have rated 1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16 4.5 out of 5.0 based on 4 product reviews. Hugely helpful service manual! Perfect. Thank you!
Manuals are all Important for Technician
This book is invaluable if you do your own repairs. Great book.
Could not find a copy until a search brought me here.
Excellent print.
Thank you