This section describes the components of the ignition system and how to adjust
them. Some tools are necessary for the adjustment procedures and a description
of those is also given. You can find and purchase most of the parts described
in this page (and some you don't see!) in the following parts catalogue pages
from VLVworld.com:
2.9.1 Distributor Cap and Rotor
The distributor cap [1] and rotor [2]
are located at the rear of the engine where the spark plug wires are connected.
The distributor mounting angle determines when each plug fires (in relation
to the camshaft position). To measure this it is necessary to use a timing
light. Attach the timing light to the battery and around the number one
spark plug wire (closest to the front on a 4 cylinder, rear left [drivers
side] on a 6 cylinder). Then run the engine and point the light at the
timing belt in front of the engine. Using the timing light it should be
possible to see the scale [10,20,30] and a marker noting the timing value.
Cap Removal Procedure
- Disconnect all the wires from the distributor (make note of where
each plug wire goes)
- Undo the three 8mm screws fastening the distributor cap
- Remove the cap
- Note the position of the rotor as it must be reinstalled at the same
angle (there is a groove to ensure it is set correctly)
- Detach the rotor from the distributor
- Reconnect in opposite manner
Timing Adjustment Procedure / Distributor Angle
- Loosen the two 10mm distributor bolts, but do not remove them
- Use a timing light to check the engine timing
- Attach the light to the battery
- Connect the current sensor around wire #1
4 cylinder- plug #1 is closest to front
6 cylinder- plug #1 is rear left (drivers side)
- Run the engine
- Point the strobing light towards the crankshaft pulley (be
very careful of the fan and other moving parts nearby)
- Look for the [10-20-30] scale and the timing mark
- Change the angle of the distributor to obtain correct timing (look
for a plate inside your engine bay to find the suggested timing, or
look up your car/engine in the VLVworld information section)
- When the correct timing is achieved tighten the two 10mm distributor
bolts
Changing a distributor
- Remove the cap and rotor (see above)
- Undo the two 10mm distributor alignment screws
- Gently pull the unit towards the firewall
- When reinstalling try and set the shaft to the same angle, so it will
align easily with the camshaft.
- Do not fully tighten the alignment screws until the timing has been
checked and the distributor angle is correct.
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Figure 2.9.1a Distributor Cap and Rotor
Figure 2.9.1b Timing Scale/Mark
Figure 2.9.1c Timing Light
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2.9.2 Spark Plugs
The spark plugs should be changed every 15,000 miles and the gap should
be checked every 6 months.
The high voltage current generated by the ignition coil passes through the
spark plug and then jumps the gap at the end, generating a spark. It is
this spark that ignites the cylinder.
If an engine is not running well inspection of the spark plugs may reveal
if oil is leaking past the piston rings, an incorrect air/fuel mixture,
or combustion deposits bridging the spark plug gap.
Changing
spark plugs
- On a COLD engine (important because of the aluminum head)
- Disconnect the plug wire (making note of it's spark plug number)
- Attach a 3/4" spark plug socket (a deep socket with a rubber insert)
- Undo the plugs
- Before reinstalling spark plugs some individuals like to apply some
anti-seize compound to the threads. However, this will alter the thread
friction when installing the plugs, so the suggested torque value may
now be too high. Use your own judgment about what is best.
- Check the gap on all plugs before installing or reinstalling (see
below)
- When installing the plugs be very careful to align it well in the
socket. It is best to start by hand. VOLVOs have an aluminum block and
it is very easy to cross thread a plug and damage the cylinder head.
- Use a torque wrench for the final tightening
- 4-cylinder: 25 ± 5 Nm [18 ± 4 Ft-lbs]
- 6-cylinder: 12 ± 2 Nm [9 ± 1.5 Ft-lbs]
Cross-Threaded Plugs
If a spark plug 'jumps' out of the socket with the engine running then the
seating thread is damaged. If the plugs have recently been changed or removed
at a garage it is best to return there as they have probably cross-threaded
the plug.
A thread insert [a small section of pipe with an interior and exterior thread]
can be bought to repair the cylinder hole. The hole is first reamed with
a hand tool and a tap is used to thread the larger hole. The thread insert
is then fit into place. After reaming and tapping the hole it is necessary
to clean out the cylinder with compressed air. Any metal fragments left
in the cylinder could do further damage. Because of the possibility of ruining
the engine block, and the tools needed, this is a procedure best left to
a professional. If the cylinder hole is easily accessible it should not
take a garage any more than half an hour to complete.
Gapping Spark Plugs (to 0.7mm/0.028 in)
- To check the spark plug gap use a spark plug gap tool (or feeler gauges)
- Insert the tool between the electrodes to measure the gap
- The gap should be 0.028 in [0.7mm]
- Manipulate the exterior electrode to achieve the correct gap distance
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2.9.2a Spark Plugs
2.9.2b Thread Insert
Figure 2.9.2c Spark Plug Gap Tools |
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2.9.3 Ignition Coil
The ignition coil converts the 12V from the battery into a high voltage,
low current charge. There are two types of wires connected to the coil:
Primary Wires- the smaller wires connected to the exterior terminals. They carry the low voltage charge to the coil.
Seondary Wire/Coil Wire (or a High-Tension Lead)- the larger centrally mounted wire. This carries the high voltage charge from the coil to the distributor.
VOLVO ignition coils rarely fail. If a problem is suspected check the wiring
to and from the coil.
To check the coil- by timing light
- Attach a timing light around the coil wire (between the coil and the distributor)
- Crank the car
- If the timing light registers current (it flashes) then current is flowing from the coil
To check the coil- by resistance
- Remove the coil from it's mount and visually inspect for cracks, leaking
insulating oil
- Clean the terminals if they look corroded. Be careful not to ground
the terminals as this may damage the coil.
- Using a multimeter test the primary reistance (between the two exterior
terminals). It should be between 0.5 ohms and 0.9 ohms.
- Test the secondary resistance (between the secondary terminal and
one of the primary terminals). It should between 6.0 K-ohms and 9.5
K-ohms.
- If the resistances were not within range replace the coil.
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2.9.3a Ignition Coil
Figure 2.9.3b Coil Terminals |
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2.9.4 Wiring
VOLVO does not list the wiring as a replacement item, although almost every
garage will change the wires as part of a 'tune up'. If the wires are damaged
or worn they should be changed. Check the insulation for damage- especially
the coil wire which passes by the exhaust manifold on some models. Poor
running in wet weather can be a sign of wiring problems. One method of checking
the wiring is to stop at night in a dark area, open the hood with the engine
running, and watch for any sparking. [Never adjust the wires or
have the connectors exposed with the engine running- risk of a powerful
electric shock.] The wiring can also become damaged at the connectors
to the distributor and plugs, so check these after disconnecting. On some
wires it is possible to pull back the connector cover. This is recommended
when reconnecting, so you can be sure that the wire is set correctly. Then
slide the cover back down the wire to insulate and protect the connector.
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Figure 2.9.4a Spark Plug Wires |
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2.9.5 Power Stage / Ignition Amplifier
The power stage, or ignition amplifier, is located on the inside wall of
the engine compartment just above the drivers side wheel well. The ignition
control unit sends a signal to the power stage once it is aware that the
engine is turning over (by the hall effect sensor [pre 88] or the RPM sensor
[88 onwards]). The power stage then amplifies this signal and sends it to
the low voltage side of the ignition coil.
The power stage is known to occasionally fail and can cause intermittent
(or permanent) running problems. |
Figure 2.9.5a Power Stage |
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2.9.6 Knock Sensor
The knock sensor is mounted under the intake manifold near cylinder number
2. It's purpose is to sense knocking (preignition) on the engine and retard the timing accordingly.
It is a difficult part to test without an osciliscope. Some mechanics suggest tapping the manifold or engine whist checking the timing to see if it retards. However, this is not recomended and hardly a reliable test.
However, the sensor cicruit can be tested: with the ignition key ON, but the engine not running, check the voltage, it should be between 1.5 and 5.0 volts.
When checking or reinstalling a knock sensor it should be tightened to 8-11
ft-lbs of torque. A loose or excessively tight sensor will not work effectively
as it will be oversensitive or ineffective. |
Figure 2.9.6a Knock Sensor |
