fuel pressure MAZDA MX-5 1994 Repair Manual

FUEL SYSTEM SYSTEM OPERATION Fuel Pressure Hold Inspection 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 "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the negative battery terminal. 2. Install a fuel pressure gauge between the fuel pipe and the fuel main hose. (Install clamps as shown.) 3. Connect the negative battery terminal. 4. Connect data link connector terminals F/P and GND with a jumper wire. 5. Turn the ignition switch ON for 10 sec. to operate the fuel Pump. 6. Turn the ignition switch OFF and disconnect the jumper wire. 7. Observe the fuel pressure after 5 min. Fuel pressure: More than 147 kPa (1.5 kgf/cm2, 21 psi) 8. If not as specified, perform the following inspections. Fuel pump hold pressure (Refer to page F-114.) Pressure regulator hold pressure (Refer to page F-118.) Fuel injector fuel leakage (Refer to page F-120.) Gartner Banana

FUEL SYSTEM Fuel Line Pressure Inspection 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 "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the negative battery terminal. 2. Install a fuel pressure gauge between the fuel pipe and the fuel main hose. (Install clamps as shown.) 3. Connect the negative battery terminal. 4. Connect data link connector terminals F/P and GND with a jumper wire. 5. Turn the ignition switch ON. 6. Measure the fuel line pressure. Fuel line pressure: 265-31 4 kPa {2.7-3.2 kgf/cm2, 38-46 psi) Pressure low- Check fuel pump maximum pressure. (Refer to page F-115.) If as specified, fuel line or fuel filter might be clogged or restricted. Pressure high- Replace the pressure regulator. (Refer to page F-118.) Gartner Banana

FUEL SYSTEM Installation note Fuel hoses and fuel filler hoses Push the ends of the main fuel hose, fuel return hose, and evaporation hose onto the fuel tank fittings L at least 25mm (1.0 in). Push the fuel filler hose onto the fuel tank pipe and filler pipe at least 35117171 (1.4 in). Power plant frame Install the power plant frame referring to the installation procedure on section J. FUEL FILTER Replacement Low-pressure side (In-tank filter) (Refer to page F-116.) High-pressure side The fuel filter must be replaced at the intervals outlined in the maintenance schedule. Warning Fuel vapor is hazardous. It can very easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel. Warning Fuel line spills and leaks are dangerous. Fuel can ~SJOFX-226 ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete the "Fuel Line Safety Procedures" on page F-108. 1. Raise the rear of the vehicle and support it with safety stands. 2. Remove the fuel filter protector. 3. Disconnect the fuel hoses from the fuel filter. 4. Remove the fuel filter and bracket. 5. Install in the reverse order of removal. 6. Verify that the fuel hoses are pushed fully onto the fuel filter nipples. Tightening torque: 7.9-10.7 N.m (80-110 kgfam, 70-95.4 in-lbf) Gartner Banana

F FUEL SYSTEM FUEL PUMP Inspection Fuel pump operation 1. Connect the data link connector terminals F/P and GND , with a jumper wire. 2. Remove the fuel filler cap. 3. Turn the ignition switch ON. 4. Listen for operational sound of the fuel pump at the filler inlet. 5. Install the fuel filler cap. 6. If no sound was heard, measure the voltage between the fuel pump connector wire to ground. Voltage: Battery positive voltage 7. If not correct, check the fuel pump relay and its circuits. (Refer to page F-116.) 8. If the voltage is normal, check for continuity between fuel pump connector (6) and a ground. 9. If there is continuity, replace the fuel pump. 10. If no continuity, repair the ground circuit. Hold pressure Perform this inspection if the fuel pressure hold inspec- tion is not as specified. (Refer to page F-109.) Warning Fuel line spills and leaks can be dangerous. Fuel can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the negative battery terminal. 2. Connect a fuel pressure gauge to the fuel main pipe and plug the outlet of the fuel pressure gauge as shown. (Install clamps as shown.) 3. Connect the negative battery terminal. Gartner Banana

FUEL SYSTEM 4. Connect data link connector terminals FIP and GND with a jumper wire. 5. Turn the ignition switch ON for 10 sec. to operate the fuel pump. 6. Turn the ignition switch OFF and disconnect the jumper wire. 7. Observe the fuel pressure after 5 min. Fuel pressure: More than 343 kPa (3.5 kgf/cm2, 50 psi) 8. If not as specified, replace the fuel pump. Fuel pump maximum pressure Warning Fuel line spills and leaks can be dangerous. Fuel can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the negative battery terminal. 2. Connect a fuel pressure gauge to the fuel main pipe and plug the outlet of the fuel pressure gauge as shown. (Install clamps as shown.) 3. Connect the negative battery terminal. 4. Connect data link connector terminals FIP and GND with a jumper wire. 5. Turn the ignition switch ON to operate the fuel pump. 6. Measure the pump maximum pressure. Fuel pump maximum pressure: 480-657 kPa (4.9-6.7 kgf/cm2, 69-95 psi) 7. Turn the ignition switch OFF and disconnect the jumper wire. 8. If not as specified, replace the fuel pump. Replacement Warning Fuel line spills and leaks can be dangerous. Fuel can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. Gartner Banana

F FUEL SYSTEM PRESSURE REGULATOR Inspection Fuel line pressure d Warning Fuel line spills and leaks can be dangerous. Fuel can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the negative battery terminal. 2. Connect a fuel pressure gauge between the fuel main pipe and the fuel main hose. (Install clamps as shown.) 3. Connect the negative battery terminal. 4. Start the engine and run it at idle. 5. Measure the fuel line pressure. Fuel line pressure: 21 6-264 kPa (2.2-2.7 kgf/cm2, 32-38 psi) Hold pressure Perform this inspection if the fuel pressure hold inspec- tion is not as specified. (Refer to page F-104.) Warning Fuel line spills and leaks can be dangerous. Fuel ,-, can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the negative battery terminal. 2. Install a fuel pressure gauge between the fuel pipe and the fuel main hose. (Install clamps as shown.) 3. Connect the negative battery terminal. 4. Connect data link connector terminals F/P and GND with a jumper wire. 5. Turn the ignition switch ON for 10 sec. to operate the fuel pump. 6. Turn the ignition switch OFF and disconnect the jumper wire. 7. Block the outlet of the pressure regulator. 8. Observe the fuel pressure for 5 min. Fuel pressure: More than 147 kPa {I .5 kgf/cm2, 21 psi) 9. If pressure is as specified, replace the pressure regula- tor. Gartner Banana

FUEL SYSTEM F Replacement Warning Fuel line spills and leaks can be dangerous. Fuel can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. 1. Disconnect the vacuum hose. 2. Disconnect the fuel return hose. 3. Remove the pressure regulator. Tightening torque: 7.9-10.7 N.m (80-11 0 kgf-cm, 70-95.4 in4bf) 4. Use new O-ring. 5. Install in the reverse order of removal. FUEL INJECTOR Inspection Operation check 1. Warm up the engine and run it at idle. 2. Listen for operational sound of the fuel injector with a screwdriver or a sound scope. 3. If no sound is heard, measure fuel injector resistance. 4. If the fuel injector resistance is OK, check wiring to the fuel injector and powertrain control module (engine) ter- minals 2U, 2V1 2Y and 22 voltages. (Refer to page F-147.) Fuel injector resistance 1. Disconnect the fuel injector harness. 2. Measure resistance of the fuel injector with an ohmme- ter. Resistance: 12-16Q (at 20°C (68°F)) 3. If not as specified, replace the fuel injector. Removal Warning Fuel line spills and leaks can be dangerous. Fuel can ignite and cause serious injuries or death and can damage the vehicle. Fuel can also irritate skin and eyes. To prevent this from happening, release the fuel pressure according to "Fuel Line Safety Procedures" on page F-108. Gartner Banana

FUEL SYSTEM 1. Disconnect the negative battery terminal. 2. Remove the PCV hose. 3. Disconnect the vacuum hose. 4. Disconnect the fuel injector connectors. 5. Remove the fuel distributor and the pressure regulator. 6. Remove the grommets, fuel injectors, and insulators. Inspection Fuel leakage test 1. Firmly affix the fuel injectors to the fuel distributor with wire. 2. Disconnect the fuel injector connectors. 3. Remove the fuel distributor and fuel injectors together with the fuel hoses connected. 4. Connect data link connector terminals FIP and GND with a jumper wire. 5. Turn the ignition switch ON. 6. Tilt the fuel injectors approx. 60 degrees and verify that no fuel leaks from the fuel injector nozzles. 7. If fuel leaks from an fuel injector, replace it. Leakage Specification If there is more than one drop per 2 minutes, replace the fuel injector. d 8. Turn the ignition switch OFF and remove the jumper wire. Gartner Banana

PRESSURE REGULATOR CONTROL SYSTEM PRESSURE REGULATOR CONTROL SYSTEM DATA LINK CONNECTOR - CLUTCH SWITCH (MT) (TEN TERMINAL) PARKINEUTRAL SWITCH (PCMT) (AT) THROTTLE POSITION SENSOR L 1 ,,,, INTAKE AIR TEMPERATURE 1 SENSOR (IN MASS AIRFLOW SENSOR) -;- ENGINE COOLANT TEMPERATURE SENSOR PRC SOLENOID VALVE CRANKSHAFT POSITION SENSOR PRESSURE REGULATOR PCME I Above 90°C {194OF} ( Above 70°C {158'F} I Throttle valve closed throttle position or no load condition I Approx. 150 1 I Operating condition Coolant temperature I Intake air temperature I Engine condition I I To prevent percolation of the fuel during hot restart idle, vacuum to the pressure regulator is momentarily cut, and the fuel injection pressure is increased to slightly more than 284 kPa (2.9 kgf/cm2, 41.2 psi}. Operating time (sec) Gartner Banana

FUEL EVAPORATIVE SYSTEM FUEL EVAPORATIVE SYSTEM DESCRIPTION The fuel evaporative system consists of the fuel vapor valve, the two-way check valve, the charcoal can- ister, the purge solenoid valve, the powertrain control module (engine), and the input devices. The amount of evaporative fumes introduced into the engine and burned is controlled by the solenoid valve in relation to the engine's operating conditions. To maintain the best engine performance, the solenoid valve is controlled by the powertrab control module (engine). THROTTLE 1-1 POSITION SENSOR I1 I I (IDLE SWITCH) 7 BAROMETIC ABSOLUTE PRESSURE SENSOR PARWNEUTRAL SWITCH (AT) MASS AIRFLOW SENSOR CRANKSHAFT POSITION SENSOR (SGT-SIGNAL) n - DUTY - LOW HIGH (ENGINE) CHARCOAL PURGE SOLENOID VALVE CANISTER HEATED OXYGEN SENSOR ENGINE COOLANT POWERTRAIN TEMPERATURE SENSOR CONTROL MODULE CHECK VALVE # 11 FUEL VAPOR VALVE Operation The purge solenoid valve is controlled by duty signals from the powertrain control module (engine) to per- form purging of the charcoal canister. Purging is done when these conditions are met: i/ 1. After warm-up. 2. Driving in gear. 3. Accelerator pedal depressed (idle switch OFF). 4. Heated oxygen sensor functioning normally. Gartner Banana