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Home >> Mazda >> 2005 >> MPV ES >> Repair and Diagnosis >> Engine Performance >> System >> Symptom Troubleshooting (Engine Control System) AJ >> No.30 Spark Plug Condition >> Diagnostic procedure
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Diagnostic procedure

SPARK PLUG CONDITION - DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1
  • Remove all spark plugs.
  • Inspect spark plug condition.
  • Is spark plug condition okay?
 Yes Troubleshooting completed.
No Specific plug is wet or covered with carbon: 
  • Go to next step.

Specific plug looks grayish white: 
  • Go to Step 7.

All plugs are wet or covered with carbon: 
  • Go to Step 9.

All plugs look grayish white: 
  • Go to Step 15.
2
  • Is spark plug wet/covered with carbon by engine oil?
 Yes Working up and down inspect all areas related to oil.
No Go to next step.
3
  • Inspect spark plug for following.
    • Cracked insulator
    • Heat range
    • Air gap
    • Worn electrode
  • Is spark plug okay?
 Yes Go to next step.
No Replace spark plug.
4
  • Inspect compression pressure at suspected faulty cylinder.
  • Is compression pressure correct?

    (See COMPRESSION INSPECTION .)

 Yes Go to next step.
No Repair or replace malfunctioning part.
5
  • Install all spark plugs.
  • Carry out spark test at suspected faulty cylinder.
  • Is strong blue spark visible? (Compare with normal cylinder.)
 Yes Go to next step.
No Repair or replace malfunctioning parts:
6 Yes Inspect fuel injector for following:
  • Open or short in injector
  • Leakage
  • Injection volume
No Zero or low: 
  • Inspect fuel pump circuit.
  • Inspect for open fuel pump relief valve.
  • Inspect for fuel leakage inside pressure regulator.
  • Inspect for clogged main fuel line.

High: 
  • Inspect pressure regulator for pressure cause.
  • Inspect for clogged fuel return line.
7
  • Inspect spark plug for following.
    • Heat range
    • Air gap
  • Is spark plug okay?
 Yes Go to next step.
No Replace spark plug.
8 Yes Inspect for open circuit between suspected fuel injector connector terminal and PCM connector following terminals:
  • For #1 cylinder:  76
  • For #2 cylinder:  50
  • For #3 cylinder:  75
  • For #4 cylinder:  49
  • For #5 cylinder:  74
  • For #6 cylinder:  48
No Replace fuel injector.
9
  • Is air cleaner element free of restriction?
 Yes Go to next step.
No Replace air cleaner element.
10
  • Carry out spark test.
  • Is strong blue spark visible at each cylinder?
 Yes Go to next step.
No Repair or replace malfunctioning part.
11
  • Carry out fuel line pressure inspection.
  • Is fuel line pressure correct?
Fuel line pressure 420-460 kPa {4.3-4.6 kgf/cm 2  , 61-66 psi} 		 Yes Go to next step.
No Zero or low: 
  • Inspect fuel pump circuit.
  • Inspect for open fuel pump relief valve.
  • Inspect for fuel leakage inside pressure regulator.
  • Inspect for clogged main fuel line.

High: 
  • Inspect pressure regulator for high pressure cause.
  • Inspect for clogged fuel return line.
12 Yes Go to next step.
No Repair or replace malfunctioning part.
13
  • Carry out purge control inspection (when engine can be started).
  • Is purge control correct?
 Yes Go to next step.
No Repair or replace malfunctioning part.
14
  • Carry out compression inspection.
  • Is compression correct?
 Yes Inspect for clogging in exhaust system.
No Repair or replace malfunctioning part.
15
  • When engine cannot be started, inspect intake-air system for air leakage.
  • When engine can be started, carry out intake manifold vacuum inspection.
  • Is air sucked in from intake-air system?
 Yes Repair or replace malfunctioning part.
No Go to next step.
16
  • Carry out fuel line pressure inspection.
  • Is fuel line pressure correct?
Fuel line pressure 420-460 kPa {4.3-4.6 kgf/cm 2  , 61-66 psi} 		 Yes Inspect following PIDs.
Inspect PCM GND condition.
No Zero or low: 
  • Inspect fuel pump circuit.
  • Inspect for open fuel pump relief valve.
  • Inspect for fuel leakage inside pressure regulator.
  • Inspect for clogged main fuel line.

High: 
  • Inspect pressure regulator for high pressure cause.
  • Inspect for clogged fuel return line.
17
  • Verify test results.
    • If okay, return to diagnostic index to service any additional symptoms.
    • If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
      • If vehicle is repaired, troubleshooting completed.
      • If vehicle is not repaired or additional diagnostic information is not available, replace or reprogram PCM.
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