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Choke - Electric Assist Ford Bronco II I

Testing & Diagnostics ~752 words

7.2-VOLT SYSTEM ALTERNATOR POWERED

On the 5.8 and 7.5L vehicles over 8500 GVW a 7.2-volt choke system is used. Electric current is received from the alternator stator terminal.

12-VOLT SYSTEM BATTERY POWERED

On the 5.8L under 8500 GVW a 12-volt choke system is used. Electric current is provided from choke relay located on the right fender apron. On the 2.0L, a 12-volt choke system is used. Electric current is provided from battery powered choke relay.

OPERATION

Electric choke assembly is attached to the carburetor choke housing. Choke assembly contains a thermostatic coil connected to heat conduction post. Electric current is supplied to the electric choke cap terminal.

Electric current creates heat being applied to thermostatic coil. Thermostatic coil expands, causing choke plate operation. Vacuum diaphragm and spring control choke pull-off after initial engine start.

LINKAGE OPERATION

  1. Ensure that engine is at normal operating temperature. Remove air cleaner. Depress throttle lever to the 1/4 open position. Rotate choke plate to fully closed position.
  2. Release choke plate. Choke plate should fully open. If binding exists, check for worn, damaged or dirty choke linkage. Repair as necessary.

2.0L (Choke Pull-Off)

  1. Depress throttle lever to the 1/2 fully open position. Place choke plate in fully closed position. Release throttle lever. This positions choke on the fast idle cam.
  2. Choke housing may require cooling to obtain choke setting. Choke housing can be cooled using choke tester. Install choke tester using manufacturer's instructions.
  3. Choke tester must be turned off at 15 second intervals until choke plate lightly closes. Position fast idle cam on the kickdown step. Choke plate should remain lightly closed.
  4. Choke housing may require cooling to ensure choke closure. Start engine and note the time required for choke plate to reach the fully open position. Time required for choke operation should be 195F50 seconds.
  5. If choke pull-off time does not meet specification, check choke cap continuity. See «CHOKE VOLTAGE CIRCUIT»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#choke-electric-assist) . Choke cap resistance should be checked. See «CHOKE CAP RESISTANCE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#choke-electric-assist__choke-cap-resistance) .

5.8L & 7.5L

  1. Ensure ignition switch is in the "OFF" position. Disconnect electrical lead from choke cap. Connect one test light lead to positive battery terminal. Attach remaining lead to choke cap terminal. Test light should glow indicating correct operation.
  2. If test light glows, proceed to step 4). If test light does not glow, connect one end of jumper wire to choke cap retaining ring. Connect remaining end to positive battery terminal. Test light should glow.
  3. Faulty connections between choke cap retaining ring and choke cap may cause test light not to glow. Connect jumper wire directly to choke cap ground. If test light glows, repair poor connections. If test light still does not glow, replace choke cap.

2.0L

  1. Connect test light lead to choke cap wire. Connect remaining lead to negative battery terminal or proper ground. Start engine and note test light. Test light should glow.
  2. Failure to light indicates open circuit. Check for open circuit to choke relay. Replace choke relay if open circuit is not found. Choke cap must be checked to ensure cap has proper ground.
  3. Connect test light lead to choke cap retaining ring. Connect remaining lead to battery positive terminal. Test light should glow. Check for improper choke cap ground if test light does not glow.

5.8L & 7.5L (Alternator Powered Choke)

  1. Connect test light lead to choke cap wire. Connect remaining lead to negative battery terminal or proper ground. Start engine and note test light. Test light should glow.
  2. Failure to light indicates open circuit. Check for open circuit between choke cap and alternator stator. Check alternator output, if open circuit is not found.

5.8L (Battery Powered Choke)

  1. Connect test light lead to choke cap wire. Connect remaining lead to negative battery terminal or proper ground. Start engine and note test light. Test light should glow.
  2. Failure to glow indicates open circuit. Check for open circuit in wire from choke relay to alternator stator. Check choke relay, if open circuit is not found.

CHOKE CAP RESISTANCE

  1. Adjust ohmmeter to scale indicating maximum of 30 ohms. Connect one ohmmeter lead to choke cap terminal. Connect remaining lead the choke cap clamp. Ensure that all connections are clean and free of oil film.
  2. Note ohmmeter reading. Reading should remain under 30 ohms but should not be zero. Repeat test several times, if reading is not within specifications.
  3. This is to ensure that false reading is not being obtained. Replace choke cap, if reading remains excessive.

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