1994 MAZDA MX-5 engine

F TROUBLESHOOTING GUIDE INSPECTION Check if battery positive voltage exists at fuel pump connector fuel pump positive terminal with jumper wire connected.(~tep 3 Check for fuel injector operating sound while crank- ing engine Check if battery positive voltage exists at fuel injector connector B terminal wire with ignition switch ON Connect data link connector terminals F/P and GND with jumper wire and check for correct fuel line pres- sure with ignition switch ON page F-110 Fuel Line pressure: 265--314 kPa f2.7-3.2 kgf/crn2, 38-46 psi) Check for correct engine compression Section B Engine compression: 1,255--883 kPa {12.&9.0 kgf/crn2, 182-1 28 psi)-300 rpm Check if spark plugs are OK WEAR AND CARBON BUILDUP BURNS PLUG GAP 1.0-l.lmm DAMAGE AND (0.040-0.043 in) DETERIORATION DAMAGE Try known good PCME and check if condition im- proves page F-144 - Yes - No Yes Yes - No Yes Yes - No - Yes ACTION Check continuity of fuel pump page F-114 Check fuel pump relay page F-117 Go to Step 7 Go to Step 6 Check PCME terminals 2A, 2U, 2V, 2Y and 22 voltages @3F page F-147 Check for open circuit in wiring between main relay and fuel injector page F-7 Go to next step Low pressure Check fuel line pressure while pinching fuel return hose 0 If fuel line pressure quickly increases, check pressure regulator page F-118 0 If fuel line pressure gradually increases, check for clog- ging between fuel pump and pressure regulator If not clogged, check fuel pump maximum pressure page F-115 Go to next step Check engine condition @3F Section B w Worn piston, piston rings or cylinder wall Defective cylinder head gasket w Distorted cylinder head Improper valve seating w Valve sticking in guide Go to next step Repair, clean, or replace Section G Gartner Banana

TROUBLESHOOTING GUIDE 3 CRANKS NORMALLY BUT WILL NOT START (PARTIAL COMBUSTION) -WHEN ENGINE IS COLD Engine cranks at normal speed but shows partial combustion and will not continue to run IESCRIPTION Battery in normal condition Fuel in tank TROUBLESHOOTING HINTS] B AirIFue! mixture too rich Q Low engine compression Air cleaner element clogged D AirIFuel mixture too lean Fuel injection control malfunction (Correction for coolant temperature) Low fuel line pressure Air leakage of intake air system 1 INSPECTION ACTION :heck if "00" is displayed on Self-Diagnosis Checker ~ith ignition switch ON as page F-79 Sheck if strong blue spark is visible at each discon- iected high-tension lead while cranking engine Connect data link connector terminals F/P and GND with jumper wire and check for correct fuel line pres- sure with ignition switch ON E+T page F-110 Fuel Line pressure: 265--314 kPa I2.7-3.2 kgf/cm2, 38-46 psi) INSTALL CLAPS ' Yes Yes Yes - No - Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage @f page F-145 Specification: Battery positive voltage (Ignition switch ON) O If OK, replace PCME page F-143 L:, If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Go to next step Check ignition system (Refer to Troubleshooting "Misfire") Section G Go to next step Low pressure Check fuel line pressure while pinching fuel return hose If fuel line pressure quickly increases, check pressure regulator page F-118 o If fuel line pressure gradually increases, check for clog- ging between fuel pump and pressure regulator If not clogged, check fuel pump maximum pressure page F-115 High pressure Check if fuel return hose is clogged or restricted O If OK, replace pressure regulator page F-119 s If not OK, repair or replace Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION Check if PCME terminal voltages are OK (IC, 1 R, IT, 2D, 20 and 2Q) page F-146 :heck for air leakage of intake air system malfunction page F-100 :heck for EGR system malfunction page F-124 Check if mass airflow sensor US page F-152 Check for correct engine compression Section B Engine compression: 1,255-883 kPa j12.8-9.0 kgf/cm2, 182-128 psil-300 rpm Check if spark plugs are OK WEAR AND CARB/ON BUILDUP BURNS PLUG GAP 1 .O-1 .l mm (0.040-4.043 in) DAMAGE AND DETERIORATION DAMAGE - Yes Yes - No Yes - No Yes - No Yes No - Yes - No - ACTION Go to next step Check for cause (Refer to "Check Point for Each Terminal") page F-148 Repair or replace Go to next step Repair or replace Go to next step Go to next step Repair or replace page F-99 Go to next step Check engine condition Section B Worn piston, piston rings or cylinder wall Defective cylinder head gasket Distorted cylinder head Improper valve seating a Valve sticking in guide Go to next step Repair, clean, or replace @a Section G Try known good PCME and check if condition im- 3rOVeS page F-144 Gartner Banana

TROUBLESHOOTING GUIDE 7 CRANKS NORMALLY BUT WILL NOT START (PARTIAL COMBUSTION) -AFTER WARM-UP I ~ngine starts normally when cold TROUBLESHOOTING HINTS] D AirIFuel mixture too rich O Vapor lock Fuel pressure not held in fuel line after engine stops High RVP (winter) fuel used in warm weather 'ESCRIPTIoN Fuel injection control malfunction (Correction for coolant temperature) Fuel injector fuel leakage I INSPECTION Engine cranks at normal speed but shows partial combustion and will not continue to run after running and hol soaked Battery in normal condition :heck if "00" is displayed on Self-Diagnosis Checker with ignition switch ON @S page F-79 :heck if PCME terminal voltages are OK :2D and 20) page F-136 sonnect data link connector terminals F/P and GND ~ith jumper wire and check for correct fuel line pres- sure with ignition switch ON page F-110 Fuel Line pressure: 26-14 kPa {2.7-3.2 kgflcm2, 38-46 psi) GND F~P INSTALL CLAPS ' Yes No - Yes - No Yes ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME page F-143 0 If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Go to next step Check for cause (Refer to "Check Point for Each Terminal") page F-148 Go to next step Low pressure Check fuel line pressure while pinching fuel return hose Q If fuel line pressure quickly increases, check pressure regulator page F-118 0 If fuel line pressure gradually increases, check fuel line and filter for clogging If not clogged, check fuel pump maximum pressure page F-115 - High pressure Check if fuel return hose is clogged or restricted a If OK, replace pressure regulator page F-119 6 If not OK, repair or replace Gartner Banana

TROUBLESHOOTING GUIDE ESCRIPTION I 0 Engine cranks at normal speed but requires excessive cranking time (more than 5 sec.) before starting Batterv in normal condition 5 I TROUBLESHOOTING HINTS] D Air/Fuel mixture too lean Q Air/Fuel mixture too rich Fuel injection control malfunction Air cleaner element clogged (Correction for coolant temperature) Mass airflow sensor stuck Low fuel line pressure 31 Poor ignition spark CRANKS NORMALLY BUT HARD TO START - ALWAYS Air leakage STEP - 1 INSPECTION Check if "00" is displayed on Self-Diagnosis Checker with ignition switch ON page F-79 Check for correct intake manifold vacuum at idle Vacuum: More than 450 mmHg (17.7 inHg} VA/CUUM GAUGE Check if air cleaner element is clean page F-76 Check for correct fuel line pressure at idle page F-110 Fuel line pressure: 265--314 kPa (2.7-4.2 kgf/cm2, 38--46 psi} (Vacuum hose to pressure regulator discon- nected) INSTALL CLAPS ' - Yes - No - Yes - No - Yes No - Yes - No - ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage page F-145 Specification: Battery positive voltage (Ignition switch ON) Q If OK, replace PCME page F-143 o If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Go to next step Check for air leakage of intake air system components page F-100 Go to next step Replace air cleaner element page F-99 Go to next step Low pressure Check fuel line pressure while pinching fuel return hose Q If fuel line pressure quickly increases, check pressure regulator page F-118 0 If fuel line pressure gradually increases, check for clog- ging between fuel pump and pressure regulator If not clogged, check fuel pump maximum pressure page F-115 Gartner Banana

TROUBLESHOOTING GUIDE INSPECTION ACTION Check if PCME terminal voltages are OK (1 R, 1 T, ZD, 20 and 20) us page F-146 Yes Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") Djp paae F-148 Check if strong blue spark is visible at each discon. nected high-tension lead while cranking engine Yes - No Go to next step Check ignition system (Refer to Troubleshooting "Misfire") Section G Check for EGR system malfunction page F-124 Yes - No Repair or replace Go to next step Check for fuel injector operating sound at each in- Yes Go to Step 10 jector at idle No - Yes Go to Step 9 Check if battery positive voltage exists at fuel injec- tor connector B terminal with ignition switch ON Check if fuel injector resistance is OK page F-119 Resistance: 12-1 6R G If OK, check wiring between injector and PCME page F-7 o If not OK, replace injector L@? page F-119 No - Yes Check wiring between main relay and fuel injector page F-7 Go to next step Check for correct engine compression Section B Engine compression: 1,255-883 kPa I12.8-9.0 kgflcm2, 182-1 28 psi)-300 rpm Check engine condition Section B I Worn piston, piston rings or cylinder wall r Defective cylinder head gasket r Distorted cylinder head r Improper valve seating Valve sticking in guide No - Yes :heck if spark plugs PLUG GAP 1 .O-1 .l mm (0.04+0.043 in} DETERIORATION 30 to next step qepair, clean, or replace Section G Try known good PCME and check if condition im- roves @r page F-144 Gartner Banana

TROUBLESHOOTING GUIDE CRANKS NORMALLY BUT HARD TO START - WHEN ENGINE IS COLD c Engine cranks at normal speed but requires excessive cranking time before starting IESCRIPTION Battery in normal condition Restarts OK after warm-up TROUBLESHOOTING HINTS] D AirIFuel mixture too rich Air cleaner element clogged Idle speed control malfunction Q AirJFuel mixture too lean Fuel injection control malfunction (Correction for coolant temperature) O Poor atomization of fuel Low RVP (summer) fuel used in cold weather INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 ACTION - Yes - No - Yes GO to next sGP Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) E+T page F-81 "88" flashes Check PCME terminal 1 E voltage page F-145 Specification : Battery positive voltage (Ignition switch ON) c:, If OK, replace PCME page F-143 o If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Check if PCME terminal voltages are OK (1 C, 2D, 20 and 2Q) page F-145 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") I@ page F-148 Check if engine starts easily when depressing ac- celerator while cranking Yes Check if idle air control valve is OK @F page F-106 o If OK, check air valve page F-105 6 If not OK, replace IAC valve page F-106 No - Yes - No Go to next step Check for correct intake manifold vacuum at idle Go to next step Vacuum: More than 450 mmHg (17.7 inHg} VACUUM GAUGE / Check for air leakage of intake air system components US= page F-1 00 Check if air cleaner element is clean @&Y page F-76 Yes - No Go to next step Replace air cleaner element page F-99 Try known good PCME and check if condition @&Y page F-144 Yes - No - Replace PCME Change fuel to another brand Gartner Banana

F TROUBLESHOOTING GUIDE [TROUBLESHOOTING HINTS] D AirIFuel mixture too rich 7 Q Vaoor lock CRANKS NORMALLY BUT HARD TO START - AFTER WARM-UP Fuel pressure not held in fuel line after engine stops 0 High RVP (winter) fuel used in warm weather ACTION DESCR'PnON Fuel injection control malfunction Fuel injector fuel leakage Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON uar page F-79 Engine cranks at normal speed but requires excessive cranking time (more than 5 sec.) before starting after run- ning and hot soaked Battery in normal condition Engine starts normally when cold 1 Check if PCME terminal voltages are OK (2D,2R and 2Q) page F-145 INSPECTION Run engine at idle and check if fuel line pressure is held after ignition switch turned OFF page F-109 Fuel line pressure: More than 147 kPa (1.5 kgf/cm2, 21 psi} for 5 min. INSTALL CLAPS Try known good PCME and check if condition im- proves US page F-144 Yes - No Yes - No Yes No - Yes Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME @sf page F-143 G If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Go to next step Block outlet of pressure regulator and check if fuel line pressure is held after ignition switch is turned OFF page F-117 If OK, replace pressure regulator page F-118 Q If not OK, check fuel pump hold pressure I@? page F-115 If fuel pump is OK, check fuel injector for fuel leakage page F-120 Replace PCME Change fuel to another brand Gartner Banana