BMW 5251 Service Manual page 100

11
3-6
Cylinder Head Removal and Installation
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Disable ignition system by removing DME main relay. See
610 Component Locations for relay location.
WARNING-
.
The ignition system produces high voltages that can be fa-
tal. Avoid contact with exposed terminals and use exfreme
caution when working on a car with the ignition switched on
or the engine running.
Do not touch or disconnect ignition components while
the engine is running or being cranked by the starter.
Failure to remove the DME main relay or attempting to disa-
bie the fuel andignition systems by other methods may result
in damaoe to the enoine control module (ECM).
-
-
Remove plastic cylinder head cover(s)
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.
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-
Remove coil grounding straps.
I
CAUTION-
I
nition system components.
I
-
Remove coils.
-
Remove spark plugs from all cylinders.
NOTE-
Check the spark plugs for oil deposits that may indicate poor
cylinder sealing, then set them aside in order. Used spark
plugs should be reinstalled in the same cylinder from which
they were removed.
4
Install compression gauge in first cylinder spark plug hole,
tight enough to form a good seal.
-
With parking brake set, transmission in PARK or NEUTRAL,
and accelerator pedal pressed to floor, crank engine with
starter. Record highest value indicated by gauge.
NOTE-
*
The compression gauge reading should increase with
each compression stroke and reach near its maximum
reading in about 4-6 strokes.
All cylinders should reach maximum compression in the
same number of strolces. If a cylinder needs significantly
more strokes to reach maximum compression, there is a
problem.