Mercury MERCRUISER, Service Manual, Page: 79 / 566

Step Diagnostic Process Details Yes No
7
Complete a compression test on the
engine.
Was a problem found?
Refer to
Section 3C
‑
Compression Gauge
Testing
.
Locate and repair the
problem. Retest the system.
Contact Mercury
Product Support.
NOTE: The crankshaft position sensor (CPS) is an exception. It will
not
set a fault if it fails completely.
Chart R5: Hard Start
This procedure is intended to diagnose a PCM 112 mechanical shift engine that readily rotates the crankshaft, but takes a long
time to start. You are here because you answered yes to step 5 of the diagnostic roadmap.
Step Diagnostic Process Details Yes No
1
Did you complete the Visual/
Physical Check?
– Go to step 2.
Perform the
Visual/
Physical Check
.
2
Use the CDS G3 service tool to check
for faults.
Are there any faults?
If a sensor has failed, it will
normally set a fault in the PCM.
For the CPS, see the note,
following.
Troubleshoot the
faults. Refer to the
PCM 112 Service
Manual
.
Go to step 3.
3
Check for bad fuel or problems with
the fuel filters.
Was a problem found?
Check for contaminated fuel.
Check fuel filters and the
water‑separating fuel filter.
Try starting the engine with a
portable tank of known good
fuel.
Check for poor fuel quality and
improper octane rating.
Use known good fuel.
Replace fuel filters.
Go to step 4.
4
Check for adequate spark at all of the
spark plugs.
Was adequate spark present?
– Go to step 5. Go to
Chart T4
.
5
Check the fuel pressure at the fuel rail.
Was the fuel pressure within
specification when the pump was
operating?
Refer to
Section 5A
‑
Fuel
Pressure Gauge Setup and
Use
.
Go to step 6. Go to
Chart T3
.
6
Is a scan tool being used?
– Go to step 8. Go to step 7.
7
Check for an ECT sensor shifted in
value.
With the engine completely cool,
measure the resistance of the ECT
sensor.
Compare the approximate temperature
of the ECT sensor to an accurate
reading of ambient air temperature.
Are the readings similar?
Refer to
PCM 112–Section 3A
‑
Component testing
.
Go to step 10.
Replace the ECT
sensor.
Retest the system.
8
Check for an ECT sensor shifted in
value.
Using the scan tool with the engine
completely cool, compare the ECT
sensor temperature with an accurate
reading of ambient air temperature.
Are the temperatures within 5.5° C
(10° F) of each other?
– Go to step 9.
Replace the ECT
sensor.
Retest system.
Troubleshooting
90-8M0099748 eng DECEMBER 2015 © 2016 Mercury Marine Page 1D-9