496
CID (8.1L)
SERVICE MANUAL NUMBER 30
Compression Test
NOTE: Compression pressure is 100 psi (690 kPa) minimum. Minimum compression re-
corded in any one cylinder should not be less than 70% of the highest recorded cylinder.
1.
Disable ignition system and remove all spark plugs.
NOTE: Use a fully charged battery when performing the following procedure.
2.
3.
Open throttle plate completely.
Starting with the compression gauge at “0,” crank the engine through 4 compression
strokes (4 puffs).
4.
5.
Record compression for each cylinder.
If some cylinders have low compression, use a pump type oil can to inject 3 squirts of
oil into each combustion chamber through the spark plug hole. Do a second compres-
sion check on each cylinder.
6.
7.
No cylinder should read less than 100 psi (690 kPa). Compression recorded on any one
cylinder should not be less than 70% of the highest cylinder.
4 characteristics may be evident:
•
•
Normal: Compression builds up quickly and evenly in each cylinder.
Piston Rings Leaking: Compression low on first stroke then increases on following
strokes, but does not reach normal. Compression improves considerably with 3
squirts of oil.
•
•
Valves Leaking: Compression low on first stroke and does not build up on following
strokes or with 3 squirts of oil.
If 2 Adjacent Cylinders Have Lower Than Normal Compression: Inject 3 squirts of oil
into the cylinders. If the compression does not increase, the cause may be a blown
head gasket between cylinders.
Page 3A-98
INDEX
90-863161 SEPTEMBER 2000
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 496 CID |
| Model Year | 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(2 votes, average: 4 out of 4)
Marine readers have rated Mercury MerCruiser 496 CID 8.1L Gasoline Marine Engines Service Manual Number 30 4.0 out of 4.0 based on 2 product reviews. How many openings for crankcaseventilation is there on
Merc 496 HO ?
Great down load . it was all there an more