How to spot bad
ignition circuit -
In 1 minute
You ride along in your Acura or Honda when
suddenly your car cuts out. As you lose momentum
your car rolls a few feet to a stop . Friends and
strangers help push your car along. You've just
experience what most likely is an ignition
fault. A simple block diagram shows you why your
car may have stopped. The battery takes it's path
from the ignition switch to the computer, igniter
and coil. (point mouse over
The first step is to check for the rocker
arm movement thru the oil filler. The next step is to check for sparks.
Remove one end of the plug wire. Insert a spark plug into the wire.
Lay the plug solid end to a suitable ground. E.g. exposed bolt,
shock may be hazardous due to abrupt body movement causing injury.
A practical step is to isolate you from ground - Do not lean on
metal body panels, plastic bumpers okay. DO NOT ATTEMPT
on a distributerless ignition system or DIS
- with lethal voltages up to 70KV.
Next step is to check
for spark at the coil. Run a ground lead (connected securely to
negative body ground) to the output port (secondary) of the coil
and allow a small gap between the ground wire and the output port.
<------Apply ground wire
very close to the secondary port.
My problem sounds like a main relay. Check for fuel.
Listen to the low whine of the fuel pump in the rear seats and
take notice of the unusual activity of the Check Engine Light (CEL).
SO -YOU STILL DON'T HAVE SPARK
Could it be something
else. Open the oil cap to see if the rocker arms are moving. This
should've been done earlier. If the rocker arms are not moving,
you will need to deal with the timing belt first. Could
it be the ignition key? Normally you should have 12V on at least
one of the coil's terminal if your ignition key switch,
fuse or other connections are working properly.
Quick lesson: An igniter receives square wave
signals ( in mA) sent from the ECU, determines
the rate of the signal and compares it to a
reference (the dwell time)
which tells it how
long to charge the coil. When the signal goes to
ground the igniter cuts off power to the coil to
produce spark. In other words, it's an integrated time management circuit combined with a
transistor. On previous generation the reluctor
gives the signal to the igniter.
spot a bad igniter :
tachometer quits abruptly or jerks around before
2. No spark at
3. No on/off voltage at
the coil's (+, - ) terminals when cranking.
The distributor rotor spins inside the distributor delivering
spark to each plug wire in a timely manner.
Should it fail there will be no spark at the
plugs, however, you will see spark at the coil. Check for spark. To spot a bad
distributor is hot to the touch.
2. No spark at
the plug wires.
3. Spark is found at the coil.
4. A cricket noise is heard from
the distributor before stalling.
spot a bad ignition switch :
stalls then restarts, then stalls after driving.
2. Car runs fine
when key slightly held at start position.
3. No battery voltage at the
coil + positive terminal.
4. There is an on/off
voltage at the coil's (+, - ) terminals when
spot a possible bad coil :
distributor was disturbed before it died.
2. No spark at
the plug wires.
3. No spark at the coil's output
(secondary.) And a running the test below confirms it.
test jigs would require:
1. Two alligator clips.
2. LED, 1-W Bulb.
3. 500 to 999-Ohm 1/4W resistor.
1. You have a three-four
pin connector at the coil.
one end of the BULB jig (test light) to the battery (+) terminal..
3. Probe the tip of the other end to any wire, preferably
the one marked ( - ) on the coil. If it's not marked then consult a diagram for your car.
the motor. A blinking light = bad coil. No
blinking = most likely, a bad igniter.
- ADVANCE USERS ONLY:
To spot which component
is bad probe pins 3 with the top LED jig
and pin 2 with the bottom test light: Warning: DO NOT BE CONFUSED.
Probing pin three with the test light (bottom jig) may destroy the
component in circuit. The igniter may be designed for 100 mA max
or input voltages of -0.3 to + 0.3. The LED jig or
modern DMM (digital multimeter) has a lhigh impedance.
Have a LED jig or DMM ready for all circuit tests before investigating
further. Always turn off ignition when not running any tests.
Clip the negative (anode) end of the LED
probe to the battery positive terminal.
Step 2. Clip the LED
probe to pin 4. Crank
the engine (assuming
Step 3. Do you see blinking? No-
ECU is bad, check for ECU codes. Yes-Coil/igniter
may be bad go to step 4.
Step 4. Connect the test light
tip to - negative terminal of the
coil, it may be labeled (-). DO NOT PROBE
IGNITER UNIT unless you have a steady
hand and sure. Crank. If no blinking check for
continuity between pin 2 and coil (-). If no
continuity stop here and solve this problem
otherwise go to step 5.
Step 5. Do you see blinking? No
- Go to step 5.1 Yes - Go to
|Step 5.1 Check
for battery voltage at igniter's (+)
terminal pin 3. If there is voltage
igniter is bad, replace it.
Check for battery voltage at
coil's (+) terminal. If there is voltage
coil is bad, replace it.
||Check coil for spark.
Step 1. Turn
Step 2. Before
disconnecting the ignition wires from the
distributor cap mark the location of the wire to
the cap. E.g. 1,2,3,4. Disconnect the ignition
Step 3. Remove the bolts. Before sliding out the distributor from the head
have a marking material (razor blade) ready to
mark the distributor camshaft end. Remove the
distributor. Mark the camshaft end to indicate
its position required for installation.
Step 4. Remove the distributor
Step 5. Unscrew the rotor's
fastener , if applicable, and remove it. If it
does not come off, with two flathead screw driver
pry it gently not damaging the sensors below it
with a cloth.
CAUTION: Any shock could destroy the coil. Do
not hammer or tap excessively.
Step 6. Remove the coil
connections and then coil, if applicable, careful
not to disturb it. Remove the igniter's connector
carefully and remove igniter.
Installation is the reverse of the procedure
except taking note below.
Step 4. Apply conducting grease
and electrical connection grease before
conduct grease on back,
Step 5. A bad bearing is
noticeable by a course and loose or wobbly spin.
Apply a small coat of lubricant into the bottom
bearing of the distributor shaft to lengthen the
life of the bearing, avoiding the sensors. A
good bearing will spin without any loose or dry
feeling and should be left alone.
Step 6. Install new or good
condition distributor shaft o-ring, coating
fresh oil on them. Install new or good condition
distributor cap o-ring, observing the condition
of the distributor cap terminal and scrape off any anomalies.
Coat fresh oil
on small o-ring only---->
The basic function
of an igniter is to permit buildup of
current in the primary of a spark coil, and then
to interrupt the flow at the proper firing time.
The resulting flyback action in the ignition coil
induces the required high secondary voltage
needed for the spark.
The primary currents needs to be
controlled to avoid damaging the coil. A
transistor controls the primary current by
completing the path to ground. The computer uses
a combination of internal control circuits and
external triggering devices such as the variable
reluctance sensors to control the spark timing.
The IC inside the igniter controls the timing and
sequencing of this transistor.
||The igniter's internal control
circuit is responsible for supplying the
primary current to the coil's primary
windings and also controlling the dwell
CAUTION: Always ground
the high-voltage port on the coil when doing
electrical tests and cranking. The igniter or
coil may destroy itself by finding another short
path to ground. Shorting the high voltage port
out won't harm the coil.
colors below are for 90-93 Accords
A. Blue for most Hondas/Acuras.
B. Blu2, Blu1 is for tach with in series
D. Yellow green (Do not test with a test lamp.)
colors below are for 86-89 Accords if applicable.
B. Lt/Grn but, at coil end Blk/Wht.
Disconnect the connectors from the distributor.