SERVICE MANUAL NUMBER 23
Poor Fuel Economy Symptom
Step
FUEL INJECTION SYSTEM TROUBLESHOOTING
Action
Value(s)
Yes
No
Definition: Fuel economy is noticeably lower than expected. Also, economy is noticeably
lower than it was on this engine at one time.
Was the “On-Board Diagnostic” (OBD)
System Check performed?
Go to OBD
1
-
-
Go to Step 2 System Check
Was visual/physical check performed?
Go to Visual/
Physical
Check
2
Go to Step 3
1.
2.
Check operators driving habits. Are
excessively heavy loads being car-
ried? Is operator accelerating too
much, too often?
If a problem is found, repair as nec-
essary.
3
System nor-
mal
Was a problem found?
-
-
Go to Step 4
Go to Step 5
1.
Check flame arrestor for dirt or being
plugged.
2.
3.
Check for fuel leaks.
If a problem is found, repair as nec-
essary.
4
5
6
Go to OBD
System
Check
Was a problem found?
1.
•
Check for proper fuel pressure.
Refer to Table A-4 in “General Sys-
tem Diagnostics” section.
If a problem is found, repair as nec-
essary.
2.
Go to OBD
System
Check
Was a problem found?
-
-
Go to Step 6
Go to Step 7
1.
Check for proper operation of Igni-
tion Control (IC) circuit and the
Knock Sensor (KS) circuit.
If a problem is found, repair as nec-
essary.
2.
Go to OBD
System
Check
Was a problem found?
1.
Remove spark plugs, check for wet
plugs, cracks, wear, improper gap,
burned electrodes or heavy depos-
its.
•
Refer to Distributor Ignition System.
NOTE: If spark plugs are gas or oil
fouled, the cause of the fouling must be
determined before replacing the spark
plugs.
7
2.
If a problem is found, repair as nec-
essary.
Go to OBD
System
Check
-
Go to Step 8
Was a problem found?
Index
90-861326--1 MARCH 1999
Page 5D-27
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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