MerCruiser 13, Service Manual

Page: 47 / 348

1C- 10 - TROUBLESHOOTING 90-816462 2-695
DISTRIBUTOR 3 TERMINAL
CONNECTOR
B R E
PICK-UP
COIL
DISTRIBUTOR
HEI MODULE
PN
BRE
BRE
+ C
+ C
FILTER
PNK
TO
DISTRIBUTOR
CAP
PUR
GRY
S
E
C
P
R
I
BLK
CONN
IGN COIL
BRN
WHT
WHT
WHT/GRN
IGNITION
COIL
CONNECTOR
(+) (“C”)
PUR GRY
A
B
A
B
71572
EST Ignition System Check
Test Description
Numbers below refer to circled numbers on the
diagnostic chart.
1. Two wires are checked, to ensure that an open is
not present in a spark plug wire.
a. If spark occurs with EST connector discon-
nected, pick-up coil output is too low for EST
operation.
2. A spark indicates the problem must be the distrib-
utor cap or rotor.
3. Normally, there should be battery voltage at the
“C” and “+” terminals. Low voltage would indicate
an open or a high resistance circuit from the dis-
tributor to the coil or ignition switch. If “C” terminal
voltage was low, but “+” terminal voltage is 10
volts or more, circuit from “C” terminal to ignition
coil or ignition coil primary winding is open.
4. Checks for a shorted module or grounded circuit
from the ignition coil to the module. The distributor
module should be turned “OFF,” so normal volt-
age should be about 12 volts. If the module is
turned “ON,” the voltage would be low, but above
1 volt. This could cause the ignition coil to fail from
excessive heat. With an open ignition coil primary
winding, a small amount of voltage will leak
through the module from the “BAT” to the “TACH”
terminal.
5. Applying a voltage (1.5 to 8 volts) to module termi-
nal “P” should turn the module “ON” and the “tach”
terminal voltage should drop to about 7-9 volts.
This test will determine whether the module or coil
is faulty or if the pick-up coil is not generating the
proper signal to turn the module “ON.” This test
can be performed by using a DC battery with a rat-
ing of 1.5 to 8 volts. The use of the test light is
mainly to allow the “P” terminal to be probed more
easily. Some digital multi-meters can also be
used to trigger the module by selecting ohms,
usually the diode position. In this position the me-
ter may have a voltage across its terminals which
can be used to trigger the module. The voltage in
the ohm’s position can be checked by using a se-
cond meter or by checking the manufacturer’s
specification of the tool being used.
6. This should turn “OFF” the module and cause a
spark. If no spark occurs, the fault is most likely in
the ignition coil because most module problems
would have been found before this point in the
procedure. A module tester could determine
which is at fault.