2001 BMW 525i ignition coil ground

Downloaded from www.Manualslib.com manuals search engine
020-21
Maintenance
Spark plugs, replacing
E39 engines use a coil-over-spark plug configuration, with
one ignition coil above each spark plug. Sparks plugs should
be removed only after the engine has cooled.
Remove engine
cover(s) over ignition coils:
Remove acoustic cover over fuel injectors
I intake
manifold.
6-cylinder engine: Remove oil filler cap.
Remove plastic trim covers (arrows).
Remove cover hold-down bolts. Remove coil
cover(s)
6-cylinder engine: Temporarily reinstall oil filler cap to
keep out contaminants.
Remove ignition coil grounding harnesses (arrows). 6-cylin-
der coils shown,
V-8 engine is similar.
< Remove ignition coils:
Pull up on spring clips to disconnect ignition coil harness
connectors.
Remove coil mounting bolts. Pull coils up and off spark
plugs.
- Remove spark plugs.

Downloaded from www.Manualslib.com manuals search engine
100-6
( Engine-General
The main grounds for the fuel and ignition circuits of the DME
system are illustrated below; see 610 Electrical Component
Locations for additional ground and component locations.
4 Ground for engine management system in right rear of en-
gine compartment on E-box bulkhead (arrow).
6-cylinder models: Grounds
for ignition coils (arrows)
4 V-8 models: Grounds for ignition coils, at cylinders 3
(arrow) and 7.
4 Fuel pump ground (arrow) below right tail light in luggage
compartment.
NOTE-
Ground location for sedan shown, wagon models may
differ.

Downloaded from www.Manualslib.com manuals search engine
11 3-6
Cylinder Head Removal and Installation
- 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)
,,I . ,. .*,.,,&- - 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.

Downloaded from www.Manualslib.com manuals search engine
. .- . --
Lr -- - - - -- Cylinder Head Removal and Installation I -
- Release pressure at compression gauge valve, then remove
gauge from spark plug hole. Repeat test for each cylinder
and compare results with values given in Table a.
Table a. Compression testing specifications
Minimum compression
6-cylinder
10-1 1 bar (142-156 psi)
V-8 12-14 bar (174-203 psi)
Maximum difference between
cylinders (all engines)
0.5 bar (7 psi)
- Compression readings may be interpreted as follows:
Low compression indicates a poorly sealed combustion
chamber.
0 Relatively even pressures that are below specification nor-
mally indicate worn piston rings
andlor cylinder walls.
Erratic values tend to indicate valve leakage.
Dramatic differences between cylinders are often a sign of
a failed head
gasket, burned valve, or broken piston ring.
- If readings are within specifications, reinstall spark plugs and
ignition coils.
NOTE-
Used spark plugs should be reinstalled in the same cylinder
from which they were removed.
Tightening torque Spark plug to cylinder head 25 Nm
(18 ft-lb)
lanition coils to cylinder head 10 Nm (7.5 ft-lb)
- Remainder of installation is reverse of removal. Be sure to re-
install all wires disconnected during test, especially ground
wires at coils and cylinder head cover (where applicable).
Wet compression test
To further help analyze the source of poorcompression,awet
compression test is the next step.
- Repeat compression test, this time squirt a teaspoon of oil
into each cylinder. The oil will temporarily help seal between
piston rings and cylinder wall, practically eliminating leakage
past rings for a short time.
- If this test yields a higher reading than "dry" compression
test, there is probably leakage between piston rings and
cylinder walls, due either to wear or to broken piston rings.
- Little or no change in compression reading indicates other
leakage, probably from valves.

Downloaded from www.Manualslib.com manuals search engine
-
Cylinder Head Removal and Installation c
q Remove secondary air inject~on check valve (arrow).
4 Remove cylinder head top cover:
Remove plastic trim caps (arrows).
Remove engine oil filler cap.
Remove cover hold down fasteners and lift off cover.
4 Remove ignition coils:
Disconnect ignition coil harness connectors.
. Remove coil mounting fasteners.
Remove coils.
Remove ground straps.
NOTE-
Make note of ground wire at mounting studs arrangement
during removal.
- Remove sparlc plugs.
- Remove cylinder head cover mounting fasteners and remove
cylinder head cover.
NOTE-
The cylinder head cover mounting bolt insulators and gas-
lets should be reinstalled in their original locations. Make
note of their arrangement during removal.

Downloaded from www.Manualslib.com manuals search engine
Cylinder Head Removal and Installation
4 If applicable, remove secondary air injection pump:
Disconnect hose at one-way valve
(A).
Remove bolts at support bracket on strut tower (arrows).
Disconnect electrical harness from bottom of secondary
air injection pump.
Remove mounting bracket from strut tower.
4 Remove ignition coils:
* Disconnect ignition coil harness connectors.
Remove coil mounting fasteners.
Remove coils.
* Remove ground straps.
CA UTIOI\C
Note location of all ground wires. Failure to reinstall grounds
can result in permanent damage to engine control module or
ignition system components.
Set coil harness to side of engine compartment
- Remove cylinder head cover mounting fasteners and remove
cylinder head cover.
NOTE-
The cylinder head cover mounting bolt insulators and gas-
ltets should be reinstalled in their original locations. Male
note of their arrangement during removal.
- Remove spark plugs
4 Remove oil baffle cover from above intake camshaft.

Downloaded from www.Manualslib.com manuals search engine
11 3-61
Cylinder Head Removal and installation I
Remove intake manifold fasteners (A).
Carefully lift intake manifold off engine while checking that all
hoses and harnesses have been disconnected.
Left cylinder head, removing, M62 engine
- Remove intake manifold as described earlier
- Remove left side exhaust manifold. See 180 Exhaust Sys-
tem.
- Drain engine coolant, then remove viscous clutch cooling
fan. See
170 Radiator and Cooling System.
WARNING -
Use extreme caution when draining and disposfng of eng~ne
coolant. Coolant is poisonous and lethal to humans andpets.
Pets are attracted to coolant because of its sweet smell and
taste.
Seek med~cal attention immediately if coolant is ingest-
ed.
4 Remove coolant manifold mounting fasteners and carefully
remove manifold.
NOTE-
Engine shown removed from engine bay
4 Remove ignition coil fasteners and coils (noting location of
ground strap).
- Remove spark plugs.

Downloaded from www.Manualslib.com manuals search engine
/Cylinder Head Removal and Installation
- Remainder of installation is reverse of removal, noting the fol-
lowing:
Use new gaskets when mounting intake
manifold. Tighten
nuts finger tight first, then torque to specification in stages
working diagonally from center out.
Be sure to reinstall ignition coil ground straps at cylinders
no.
3 and no. 7. See 120 Ignition System.
Reinstall cooling fan and shroud. See
170 Radiator and
Cooling System.
Refill and bleed cooling system as described in
170 Radi-
ator and Cooling System.
Change engine oil and filter as described in
020 Mainte-
nance.
CA UTIOG
To prevent damaging engine electricalsystems, be sure to in-
stall all ground wires previously removed.
Tightening torques
Camshaft sprocket to camshaft 15
Nm (11 H-lb)
Coolant manifold to cylinder head 10 Nm (7.5 H-lb)
Cylinder head cover nuts 10 Nm (7.5 ft-lb)
Exhaust manifold to head 22 Nm (17 ft-lb)
Engine mounts to subirame 42 Nm (30 ft-lb)
Spark plugs to cylinder head 22 Nm (17 ft-lb)
Right cylinder head, removing, M62 engine
- Remove left side exhaust manifold. See 180 Exhaust Sys-
tem.
- Remove intake manifold. See Intake manifold, removal
and installation,
M62 engine.
- Drain engine coolant. See 170 Radiator and Cooling Sys-
tem.
WARNING-
Use extreme caution when draining and disposing of engine
coolant.
Coolanl is poisonous andlellial lo liumans andpels.
Pets are
altracled to coolant because of 11s sfieet smell and
fasle. Seelc medcal anenfion immed~alely if coolant is ingesl-
. .-
< Remove engine coolant manlold mo~nlng fasreners and
carei~lly remove manifo d.
. I
NOTE
Engine 8s slioivn removed lor clarify