Ignition System - Tfi-Iv Ford Bronco II I

MODEL COVERAGE

MODEL COVERAGE

DESCRIPTION

All EEC-IV controlled engines use the Thick-Film Integrated (TFI-IV) ignition system. The TFI-IV distributor contains an integrally mounted TFI-IV ignition module. A Hall Effect stator assembly replaces the coil stator. This distributor does not use conventional centrifugal/vacuum advance mechanisms.

The TFI-IV ignition module is contained in molded thermoplastic and is mounted on base of distributor. The TFI-IV ignition module used on manual transmission equipped vehicles features a push start mode. This feature allows vehicle to be push started if necessary. An "E" core ignition coil is used.

OPERATION

The TFI-IV distributor uses a Hall Effect switch mechanism to switch primary voltage and to trigger the discharge of high secondary voltage. Crankshaft position and load signal is supplied to the EEC-IV Electronic Control Assembly (ECA) to compute spark advance. Distribution of high secondary voltage is accomplished through a conventional cap, rotor, and spark plug wires.

The Profile Ignition Pickup (PIP) assembly generates a signal, which indicates crankshaft position and RPM. The PIP signal is supplied to and processed by the ECA. The ECA outputs a Spark Output Signal (SPOUT). The SPOUT signal is transmitted to the TFI-IV module to control ignition timing. (Scheme 2)

IGNITION COIL SECONDARY VOLTAGE

1. Connect Spark Tester (D81P-6666-A) between ignition coil wire and engine ground. Crank engine. If spark occurs at tester gap, system is okay. Inspect distributor cap and rotor for damage or carbon tracking. Ensure rotor tip is coated with silicone dielectric compound. NOTE: DO NOT use dielectric compound on multi-point rotor.
2. If no sparks occur, measure resistance of ignition coil wire. Replace wire if resistance exceeds 7000 ohms per foot. Inspect ignition coil for damage or carbon tracking. Crank engine and check distributor rotation. If these items are okay, go to IGNITION COIL PRIMARY CIRCUIT SWITCHING test.

Scheme 1

Scheme 2

IGNITION COIL PRIMARY CIRCUIT SWITCHING

1. Place ignition switch in "OFF" position. Disconnect wiring harness connector from ignition module. Inspect connector for dirt, corrosion and damage. Repair if necessary. If okay, reconnect harness. Connect a non-powered 12-volt test light between coil "TACH" terminal and engine ground. (Scheme 3)
2. Crank engine and observe test light. If test light comes on or flashes, remove test light. Proceed to IGNITION COIL PRIMARY RESISTANCE test.
3. If test light does not light or if it is very dim, remove test light. Proceed to «PRIMARY CIRCUIT CONTINUITY»(/ford/bronco-ii/i-1984-1990/remont/ignition-system/#ignition-system-tfi-iv__primary-circuit-continuity) test.

Scheme 3

IGNITION COIL PRIMARY RESISTANCE

1. With ignition switch in "OFF" position, disconnect ignition coil connector. Inspect connector for dirt, corrosion or damage. Measure resistance across ignition coil positive and negative terminals. (Scheme 4)
2. Resistance should measure.3-1.0 ohm. If so, ignition coil primary circuit is okay. Proceed to IGNITION COIL SECONDARY RESISTANCE test. If resistance is less than.3 ohm or greater than one ohm, replace ignition coil.

IGNITION COIL SECONDARY RESISTANCE

1. With ignition switch in "OFF" position, disconnect ignition coil connector and secondary wire from coil tower. Measure resistance between negative coil terminal and coil tower. (Scheme 4)
2. Resistance should measure 6500-11,500 ohms. If so, ignition coil is okay. Proceed to WIRING HARNESS test. If resistance is less than 6500 ohms or greater than 11,500 ohms, replace ignition coil.

Scheme 4

WIRING HARNESS

1. Disconnect wiring harness connector from ignition module. Inspect connector for dirt, corrosion or damage. Disconnect wire at "S" terminal of starter solenoid.
2. Attach negative voltmeter lead to distributor base. Measure battery voltage. With negative lead of voltmeter still connected to distributor base, check voltages at TFI-IV ignition module wiring harness terminals. (Scheme 5) See WIRING HARNESS TEST table. WIRING HARNESS TEST Connector Terminal No. Wire (Circuit) Ignition Switch Test Position 2 Coil-Terminal "RUN" 3 Run "RUN" or "START" 4 Start "Start"
3. If all readings are at least 90% of battery voltage, wiring harness and connectors are okay. Go to STATOR test. If reading is less than 90% of battery voltage, inspect wiring harness and connectors. Also check for a worn or damaged ignition switch. Repair or replace as necessary. Turn ignition off. Remove voltmeter. Connect "S" terminal to starter solenoid.

Scheme 5

STATOR

1. Turn ignition switch to "OFF" position. Remove and ground coil wire. Attach digital voltmeter negative lead to distributor base. Disconnect spout in-line connector near distributor. Attach positive lead to ignition module side of connector.
2. Place ignition switch in the "ON" position. Using ignition key, bump starter 4-5 times and measure voltage while engine is stationary. Allow digital voltmeter reading to stabilize before taking measurement. Record all values.
3. If lowest reading is less than 0.5 volts, replace stator assembly. If highest reading is less than 70% of battery voltage, but the lowest reading is greater than 0.5 volts, remove TFI-IV ignition module from distributor.
4. Inspect stator and TFI-IV terminals for misalignment or damage. If terminals are okay, replace stator assembly.
5. Measure resistance between TFI-IV module terminals. (Scheme 6) Refer to the TFI-IV MODULE RESISTANCE VALUES table.

Scheme 6

TFI-IV MODULE RESISTANCE VALUES

TFI-IV IGNITION MODULE

1. Disconnect "Spout" in-line connector at TFI-IV module. Connect Spark Tester (D81P-6666-A) between ignition coil and engine ground. (Scheme 7) Crank engine and check for spark at tester. If no spark occurs, perform «IGNITION COIL PRIMARY RESISTANCE»(/ford/bronco-ii/i-1984-1990/remont/ignition-system/#ignition-system-tfi-iv__ignition-coil-primary-resistance) test.
2. If spark occurs, check Profile Ignition Pick-Up (PIP) and ignition ground wires for continuity. Repair as necessary. If these items are okay, go to appropriate ELECTRONIC ENGINE CONTROL IV article in COMPUTERIZED ENGINE CONTROL section listed below.

1984

1. «2.8L EEC IV TESTING»(ref-94795)
2. «4.9L EEC IV TESTING»(ref-94796)
3. «5.0L/5.8L EEC IV TESTING»(ref-94797)
4. «EEC IV THEORY/OPERATION»(ref-94798)

1985

1. «2.8L FEEDBACK CARBURETOR TESTS W/CODES»(ref-94799)
2. «4.9L FEEDBACK CARBURETOR TESTS W/CODES»(ref-94800)
3. «5.0L/5.8L FEEDBACK CARBURETOR TESTS W/CODES»(ref-94801)
4. «EEC IV THEORY/OPERATION»(ref-94802)

1986

1. «2.3L EFI EEC IV TESTING»(ref-94803)
2. «2.8L FEEDBACK CARBURETOR EEC IV TESTING»(ref-94804)
3. «2.9L EFI EEC IV TESTING»(ref-94805)
4. «3.0L EFI EEC IV TESTING»(ref-94806)
5. «4.9L FEEDBACK CARBURETOR EEC IV TESTING»(ref-94807)
6. «5.0L EFI EEC IV TESTING»(ref-94808)
7. «EEC IV THEORY/OPERATION»(ref-94809)

1987

1. «CEC DIAGNOSIS & TESTING»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing)
2. «EEC IV THEORY/OPERATION»(/ford/bronco-ii/i-1984-1990/remont/theory-operation/#eec-iv-theoryoperation)

1988

1. «EEC-IV CEC SYSTEM»(ref-94812)
2. «EEC IV THEORY/OPERATION»(ref-94813)

Scheme 7

PRIMARY CIRCUIT CONTINUITY

1. Disconnect wiring harness connector from ignition module. Inspect connector for dirt, corrosion or damage. Repair if necessary. Connect negative voltmeter lead to distributor base and measure voltage at battery.
2. With negative voltmeter lead still connected to distributor base, insert positive lead into connector terminal No. 2. (Scheme 5) Place ignition switch in "RUN" position and measure voltage at terminal No. 2.
3. If reading is 90% of battery voltage, turn ignition off. Proceed to «WIRING HARNESS»(/ford/bronco-ii/i-1984-1990/remont/ignition-system/#ignition-system-tfi-iv__wiring-harness) test. If reading is less than 90% of battery voltage, turn ignition off. Connect wiring harness. Proceed to IGNITION COIL PRIMARY VOLTAGE test.

IGNITION COIL PRIMARY VOLTAGE

1. Attach negative voltmeter lead to distributor base. Measure voltage at battery. Turn ignition switch to "RUN" position. Measure voltage at coil negative terminal.
2. If reading is 90% of battery voltage, turn ignition off. Proceed to «WIRING HARNESS»(/ford/bronco-ii/i-1984-1990/remont/ignition-system/#ignition-system-tfi-iv__wiring-harness) test. If reading is less than 90% of battery voltage, turn ignition off. Connect wiring harness. Proceed to IGNITION COIL SUPPLY VOLTAGE test.

IGNITION COIL SUPPLY VOLTAGE

1. Connect negative voltmeter lead to distributor base. Measure voltage at battery. With negative voltmeter lead still connected to distributor base, insert positive lead into coil positive terminal.
2. Place ignition switch in "RUN" position. Measure voltage at coil positive terminal. If reading is 90% of battery voltage, turn ignition off. Inspect ignition coil connector and terminal for dirt, corrosion or damage. If necessary, replace ignition coil.
3. If reading is less than 90% of battery voltage, turn ignition off. Inspect wiring harness between ignition coil and ignition switch for an open circuit. Also check for a worn or damaged ignition switch. When testing is complete, reconnect ignition module harness connector.

DISTRIBUTOR (4.9L PICKUP)

Note. The 4.9L pickup is equipped with a TFI-IV distributor. Except for the cap, adaptor, rotor, TFI module and "O" ring, no other distributor assembly parts are replaceable. There is no calibration required with the universal distributor.

Removal

1. Rotate engine until No. 1 piston is on compression stroke. Align timing marks for correct initial timing. Disconnect the primary wiring connector from distributor. Prior to removing the distributor cap, mark the position of the No. 1 wire tower on the distributor base for installation.
2. Remove the distributor cap and plastic adaptor. The plastic adaptor attaches to the distributor with screws and contains the distributor cap hold-down clips. Position them and the attached wires out of the way. Remove the rotor and place it out of the way to avoid damage. Remove the TFI connector.
3. Remove the distributor hold-down bolt and clamp and remove the distributor. Do not rotate engine while distributor is removed.

Installation

1. For engines that have not been rotated with distributor removed, go to step 2 . If engine has been rotated with distributor removed, rotate engine until No. 1 piston is on compression stroke. Align crankshaft timing marks for initial timing.
2. Install the rotor. Rotate the distributor shaft so that the rotor tip is pointing toward the mark previously made on the distributor base. Continue rotating slightly so that the leading edge of the vane is centered in the vane switch stator assembly.
3. Rotate the distributor in the engine block to align the leading edge of the vane and the vane switch and verify that the rotor is pointing at No. 1 cap terminal. If the vane and vane switch cannot be align by rotating the distributor in the engine block, pull distributor out of the block enough to disengage the distributor and rotate the distributor to engage a different distributor gear tooth.
4. Install distributor hold-down bolt and clamp. Do not tighten at this time. Connect distributor TFI and primary wiring harnesses. Install the distributor cap adaptor and tighten the attaching screws to 25-35 INCH lbs. (2.8-2.9 N.m).
5. Install the distributor cap with attached wires. Check that the ignition wires are securely attached to the cap and spark plugs.
6. Set ignition timing, with a timing light, to specification. See «ADJUSTMENTS»(ref-92154-S21659011312002071100000) in 6-CYLINDER TUNE-UP article. Tighten distributor hold-down bolt to 17-25 ft. lbs. (23-34 N.m). Check and adjust timing , if necessary.

OVERHAUL

Note. TFI-IV distributor parts replacement include cap, rotor, module, octane rod and distributor shaft "O" ring. If any other component is found to be defective, the entire distributor assembly must be replaced.

Scheme 8

See also:
• CEC DIAGNOSIS & TESTING
• EEC IV THEORY/OPERATION
• PRIMARY CIRCUIT CONTINUITY
• IGNITION COIL PRIMARY RESISTANCE
• WIRING HARNESS