Home ReviewsRefund
Home/Acura/Integra/Acura Integra I (1985-1990)/Repair manual/Testing & Diagnostics/Fuel Evaporation System
Contents Section: Testing & Diagnostics All sections

Fuel Evaporation System Acura Integra I

Testing & Diagnostics 4 illustrations ~1008 words

DESCRIPTION

Evaporative system minimizes the amount of fuel vapor released into the atmosphere. All models are equipped with a charcoal canister, purge control valve, 2-way valve, and connecting hoses and lines.

Legend models use a thermo valve to control vacuum to purge control valve, while Integra models with Electronic Fuel Injection (EFI) use an Electronic Control Unit (ECU) and purge cut-off solenoid valve. Legend models use a fuel cut-off valve and liquid/vapor separator to prevent liquid fuel from entering the 2-way valve.

CARBURETED ENGINES

When fuel tank pressure exceeds a preset value, 2-way valve opens and allows excess vapor to vent into canister. If excessive vacuum forms in fuel tank, 2-way valve opens and outside air enters fuel tank through canister. Fuel filler cap acts as a safety valve if evaporation system fails.

Thermo valve closes and allows manifold vacuum to open purge control valve when engine coolant temperature exceeds preset temperature.

FUEL INJECTED ENGINES

When fuel tank pressure exceeds a preset value, 2-way valve opens and allows excess vapors to vent into canister. If excessive vacuum forms in fuel tank, 2-way valve opens to allow outside air into fuel tank through canister. Fuel filler cap acts as a safety valve if evaporation system fails.

When coolant temperature is above a preset value, purge cut-off solenoid valve on Integra or thermo valve on Legend models, along with the ECU, directs manifold vacuum to purge control valve to draw vapor into throttle body port. When coolant temperature is below this temperature, no vacuum is applied to purge control valve.

Scheme 1

Scheme 1: FUEL INJECTED ENGINES
Scheme 1: FUEL INJECTED ENGINES

MAINTENANCE

Inspect system and test components every 60,000 miles or every 5 years. Check all hoses and lines for deterioration, damage, and obstructions.

THERMO VALVE & PURGE CONTROL VALVE

  1. Ensure vacuum lines are properly routed and are not damaged or obstructed. With engine coolant temperature below a designated thermosensor operating temperature, disconnect upper vacuum hose from purge control valve. Refer to «THERMO SENSOR OPERATING TEMPERATURE»(/acura/integra/i-1985-1990/remont/testing-diagnostics/#fuel-evaporation-system) table for specific temperature.
  2. Connect vacuum gauge to hose. Start engine and let idle. Vacuum should not be present. If there is vacuum on Integra models, test purge cut-off solenoid valve. See «PURGE CUT-OFF SOLENOID VALVE»(/acura/integra/i-1985-1990/remont/testing-diagnostics/#fuel-evaporation-system) test. If there is vacuum on Legend models, replace thermo valve. Retest thermo valve. THERMO SENSOR OPERATING TEMPERATURE Application Operating Temperature °F (°C) Integra 149 (65) Legend Coupe 158 (70) Except Coupe Auto. Trans. 158 (70) Man. Trans. 131 (55)
  3. On all models, if there is no vacuum, remove vacuum gauge and reconnect hose. With engine coolant temperature above specified temperature, disconnect upper vacuum hose from purge control valve. Run engine at idle and observe vacuum gauge. On Integra models, vacuum should be present, after 5 seconds of operation.
  4. If there is no vacuum on Integra models, test purge cut off solenoid valve. See «PURGE CUT-OFF SOLENOID VALVE»(/acura/integra/i-1985-1990/remont/testing-diagnostics/#fuel-evaporation-system) test. If there is no vacuum on Legend models, replace thermo valve and retest.

Scheme 2

Scheme 2
Scheme 2

CHARCOAL CANISTER

  1. Connect tachometer to engine. Start and warm engine to normal operating temperature. Remove fuel filler cap. Remove canister purge air hose from frame rail and connect vacuum gauge. (Scheme 3) Raise engine speed to 3500 RPM. Observe vacuum gauge. Vacuum should appear within one minute. If vacuum appears, remove test equipment, install fuel filler cap, and reconnect hose.
  2. If no vacuum is present, or does not appear within one minute, stop engine. Disconnect vacuum gauge. Install fuel filler cap. Remove canister. Inspect canister for damage. If defective or damaged, replace. Repeat test.
  3. If canister is not defective, disconnect upper vacuum hose from purge control valve port on canister. Connect hand vacuum pump to purge port. Apply vacuum. Vacuum should remain steady. If vacuum drops, replace canister. Repeat test.
  4. If vacuum remains steady, reconnect hose to purge control valve port. Start engine and let idle. Purge port vacuum should drop to zero. If not, replace canister. Repeat test.

Scheme 3

Scheme 3
Scheme 3

2-WAY VALVE

  1. Remove fuel filler cap. Remove fuel vapor hose from liquid/vapor separator pipe on Legend models, or vapor hose from fuel tank to 2-way valve on Integra models. Connect vacuum/pressure pump with gauge to hose. Slowly draw vacuum while observing gauge.
  2. Vacuum should stabilize at .2-.6 in. Hg as 2-way valve opens. Reverse pump and gauge connections. Slowly pressurize vapor hose. Pressure should momentarily stabilize at 1.0-2.2 in. Hg as 2-way valve opens.
  3. If valve does not respond as outlined, check hose connections for leaks. If hose connections are okay, replace valve. Repeat test.

Scheme 4

Scheme 4: Integra (Engine Cold)
Scheme 4: Integra (Engine Cold)
  1. With coolant temperature below 149°F (65°C), start engine and let idle. Disconnect vacuum hose No. 12 from intake manifold. Check for vacuum. (Scheme 4) If vacuum is not present, check vacuum port. If vacuum is present, check vacuum hose for proper connection, blockage and cracks. If vacuum line is okay, reconnect hose.
  2. Disconnect 6-wire connector near control box at center of firewall. (Scheme 4) Using voltmeter, connect positive probe to Black/Yellow terminal of connector and negative probe to Red/White terminal of connector. If voltage is present, replace solenoid valve. Repeat test.
  3. If voltage is not present, move negative probe of voltmeter to good body ground. Check for voltage. If voltage is not present, repair open in Black/Yellow wire between solenoid valve and 10-amp fuse in fuse block (fuse No. 4).
  4. If voltage is present, check for open in Red/White wire between solenoid valve and ECU. If wire is okay, check ECU. Remove test equipment. Reconnect all electrical connectors.

Integra (Engine Warm)

  1. Start and warm engine to normal operating temperature. Stop engine. Disconnect 6-wire connector near control box at center of firewall. (Scheme 4) Using voltmeter, connect positive probe to Black/Yellow terminal of connector and negative probe to Red/White terminal of connector.
  2. Start engine and let idle. Observe voltmeter for voltage reading 5 seconds after engine is started. If voltage is present, check for short in Red/White wire between solenoid valve and ECU. If wire is okay, check ECU. If voltage is not present, replace solenoid valve. Repeat test. Remove test equipment. Reconnect all electrical connectors.

More articles — Engine Performance