1994 MAZDA MX-5 fuel

TROUBLESHOOTING GUIDE DIAGNOSTIC INDEX Cranks normally but will not start (No com- Engine cranks at normal speed but shows no sign of bustion) I #firingN I F-17 I No. 1 TROUBLESHOOTING ITEM Will not crank or cranks slowly -- -- Cranks normally but will not start (Partial combustion) -When engine is cold Cranks normally but will not start (Partial combustion) - After warm-up Cranks normally but hard to start - Always Cranks normally but hard to start - When engine is cold - Engine cranks at normal speed but shows partial com- bustion and will not continue to run Engine cranks at normal speed but shows partial com- bustion and will not continue to run after running and hot soaked Engine cranks at normal speed but requires excessive cranking time (more than 5 sec.) before starting Same condition as No.5 when engine is cold Restarts OK after warm-up 8 DESCRIPTION Refer to Engine Electrical System Low idle speed1Rough idle - Before warm- UP Low idle speed/Rough idle -After warm-up PAGE SECTION G Cranks normally but hard to start - After warm-up Rough idle - Always Engine speed low or engine vibrates excessively at idle during warm-up Engine runs normally at idle during warm-up but vi- brates excessively after warm-up High idle speed - After warm-up Low idle speed - When NC, PIS, or EIL ON l5 1 Engine stalls at idle - Always Engine starts normally but vibrates excessively and stalls at idle in every condition I F40 1 13 14 Same condition as No.5 after running and hot soaked Starts normally when cold Engine vibrates excessively at idle in every condition Engine idle excessive for operation mode Engine speed decreases at idle when NC, PIS, or EIL is ON 18 1 Engine stalls during start-up 1 Engine unexpectedly stops running while starting I F-45 F-26 F-27 F-34 F-36 Rough idle just after starting Idle moves up and down 16 17 l9 1 Engine stalls on deceleration I Engine unexpectedly stops running while decelerating or after deceleration Engine starts normally but vibrates excessively only just after starting Engine speed up and down periodically at idle Engine stalls at idle - Before warm-up Engine stalls at idle - After warm-up Engine stalls at idle -When AIC, PIS, or EIL running at idle when 1 20 1 ON I F-50 1 F-37 F-38 I I . . I 21 1 Engine stalls suddenly (Intermittent) I Engine intermittently stops running I F-52 Engine starts normally but vibrates excessively and stalls at idle before warm-up Engine runs normally at idle during warm-up but be- comes rouclh and stalls after warm-up F-43 F-44 24 1 Lack of power Performance is poor under load Maximum speed re- 1 duced I F-57 I Hesitates/Stumbles on acceleration Surges while cruising I I I 25 / Poor acceleration I Performance is poor while accelerating 1 F-61 I Flat spot occurs just after accelerator is depressed or mild jerking occurs during acceleration Unexpected, usually repetitive change in engine speed Knocking F-53 F-55 Runs rough on deceleration1Afterburn Abnormal combustion accompanied by audible "ping- ing" noise I F-67 I Engine runs rough while decelerating and abnormal combustion in exhaust system 1 30 1 High oil consumption I Oil consumption excessive I F-70 1 F-65 28 1 Fuel odor 29 / Exhaust sulfur smell 1 31 1 Poor fuel economy I Fuel economy unsatisfactory I F-71 I Gasoline odor in cabin Exhaust gas smells abnormal (rotten egg smell) F-69 F-70 Gartner Banana

TROUBLESHOOTING GUIDE Warning Fuel vapor is hazardous. It can very easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel. Fuel in the fuel system is under high pressure when the engine is not running. 4 Warning Fuel line spills and leaks are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete the following "Fuel Line Safety Procedures". 35UOFX-008 F-73 F-73 F-74 Fuel Line Safety Procedures A. Release the fuel pressure before disconnecting a fuel line. 1. Start the engine. u 2. Disconnect the fuel pump relay connector. 3. After the engine stalls, turn the ignition switch to OFF. 4. Reconnect the fuel pump relay connector. B. Avoid leakage. 1. When disconnecting a fuel line hose, wrap a rag around it to protect against fuel leakage. 2. Plug the hose after removal. C. Install hose clamps to secure the fuel pressure gauge connections. Self-Diagnosis Checker does not indicate Diagnostic Trouble Code No. but MIL comes on Self-Diagnosis Checker indicates Diagnostic Trouble Code No, of input device but MIL never comes ON Blower fan operates but no cool air is discharged 32 33 34 Pinching Hose When pinching an air hose or fuel hose with pliers, wrap the hose with a rag to prevent damage. MIL always ON MIL never ON NC does not work Checking ignition spark When checking ignition spark condition, hold the high- tension lead with insulated pliers. Note If a timing light is used to check for spark, some lights do not light at the number 2 and 4 cylinders even if the ignition system is normal. J Gartner Banana

TROUBLESHOOTING GUIDE SYMPTOM TROUBLESHOOTING 2 CRANKS NORMALLY BUT WILL NOT START (NO COMBUSTION) Engine cranks at normal speed but shows no sign of "firing" ESCwPTION : Battery in normal condition Throttle valve not held wide open throttle while cranking Fuel in tank rROUBLESHOOTlNG HINTS] ecause of no combustion, possibly no fuel is injected to engine or no ignition at all cylinders 1 No spark O Low fuel line pressure lanition control malfunction @ Low engine compression ignition system component malfunction I No fuel injection Fuel pump does not operate Fuel injector does not operate INSPECTION ACTION :heck if strong blue spark is visible at disconnected iigh-tension lead while cranking engine :heck if "00" is displayed on Self Diagnosis Checker ~ith ignition switch ON page F-79 Sonnect data link connector terminals F/P and GND ~ith jumper wire and check for fuel pump operating sound with ignition switch ON page F-114 Yes - No - Yes No - Yes - No Go to Step 3 Go to Step 2 Check ignition system (Refer to Troubleshooting "Misfire") mf Section G Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage ojg. page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME us? page F-143 Q If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Check if engine starts in this condition 0 If starts, check fuel pump relay f@ page F-117 r3 If does not start, go to Step 5 Go to Step 4 Gartner Banana

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 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

F TROUBLESHOOTING GUIDE INSPECTION With condition of step 3, check if fuel line pressure is held after ignition switch is turned OFF page F-109 Fuel line pressure: More than 147 kPa (1.5 kgf/cm2, 21 psi) for 5 min. PRESSURE MINIMUM IGNITION 5 MIN. TIME SWITCH OFF Check if fuel line pressure is held after ignition switch is turned OFF and blocking outlet of pressure regula- tor page F-118 Fuel line pressure: More than 147 kPa {I .5 kgf/cm2, 21 psi) for 5 min. Try known good PCME and check if condition page F-144 - Yes - No - Yes - No - Yes ACTION 30 to Step 6 30 to Step 5 3eplace pressure regulator EF page F-119 :heck fuel pump hold pressure page F-114 3 If OK, check fuel injector for fuel leakage page F-120 3 If not OK, replace fuel pump page F-115 qeplace PCME 2hange fuel to another brand 35UOFX-O' 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