Ignition System - Electronic Toyota 4Runner I

DESCRIPTION

The Nippondenso electronic ignition system consists of a breakerless distributor, an ignition module, a pick-up coil, ignition coil, and related wiring. Distributor contains a reluctor, breaker plate, and pick-up coil assembly.

Toyota Pickup and 4Runner models use Electronic Spark Advance (ESA). The ESA system uses a computer to control ignition timing. All other models contain conventional centrifugal and vacuum advance mechanisms.

OPERATION

On ESA system, the Electronic Control Unit (ECU) is preprogrammed with data for optimum ignition timing under any engine operating condition. Using data from engine sensors (RPM, engine temperature, etc.), the ECU triggers ignition system to provide a spark at precisely the right instant. (Scheme 1)

On all other models, as distributor shaft turns reluctor, reluctor teeth (one for each cylinder) pass magnetic pick-up coil assembly. As air gap changes with approach and pass of each reluctor tooth, magnetic field varies creating a signal in pick-up coil assembly.

Ignition module senses this signal and turns ignition coil primary circuit on and off. This causes magnetic field in coil primary winding to collapse, resulting in a voltage surge in secondary winding, which fires spark plugs.

Toyota Cressida ESA Ignition System Circuit Circuit on other models is similar. Scheme 1

AIR GAP

1. Using a flat, non-magnetic feeler gauge, check air gap between pick-up coil and reluctor. (Scheme 2) Air gap should be within.008-.016" (.20-.40 mm).
2. If air gap is incorrect, remove ignition coil (if equipped) and replace distributor assembly. On Pickup and 4Runner 22R engine, replace pick-up coil/breaker plate assembly.

Checking Pick-Up Coil Air Gap. Scheme 2

SPARK TEST

1. Check ignition coil and distributor connections. On Celica 3S-FE engine, remove spark plugs and spark plug wires. Attach spark plugs to wires and ground plugs. On all other models, disconnect ignition coil wire from distributor and hold wire about 1/2" away from ground.
2. Crank engine and check for spark. If sparks occur, check for other source of starting problem. If no sparks occur, remove distributor cap and check ignition wire resistance. If wires are okay, go to next step. If not, replace wires as required. NOTE: To prevent gasoline from being sprayed from injectors, crank engine for no more than 2 seconds at a time.
3. Place ignition switch in "ON" position. Check for voltage at ignition coil positive terminal. If voltage is present, go to next step. If not, check wiring between ignition switch, coil, and ignition module.
4. Check ignition coil resistance. See «IGNITION COIL RESISTANCE TESTS»(/toyota/4runner/i-1984-1989/remont/ignition-system/#ignition-system-electronic) in this article. If coil resistance is correct, go to next step. If not, replace ignition coil.
5. Check pick-up coil resistance. See «PICK-UP COIL RESISTANCE TEST»(/toyota/4runner/i-1984-1989/remont/ignition-system/#ignition-system-electronic) in this article. If resistance is correct, go to next step. If not, remove coil and replace distributor assembly.
6. Check air gap between reluctor and pick-up coil. If air gap is incorrect, remove coil and replace distributor assembly. If air gap is correct, replace ignition module (Celica 3S-FE engine only). On all other models, go to next step.
7. Check for "IGt" ignition signal from ECU at ignition module. If reading is about one volt, replace ignition module. If not, check wiring between ECU, distributor, and ignition module. If wiring is okay, replace ECU.

Primary Coil Resistance

Isolate coil from remainder of system. Measure resistance between coil positive and negative terminals. See IGNITION COIL RESISTANCE table.

Secondary Coil Resistance

Isolate coil from remainder of system. Measure resistance between coil positive terminal and to coil tower. See IGNITION COIL RESISTANCE table.

Coil Insulation Resistance

Isolate coil from remainder of system. Measure resistance between ignition coil positive terminal and distributor housing. Reading should exceed 10 megaohms (infinity).

IGNITION COIL RESISTANCE

IGNITION WIRE RESISTANCE

1. Set ohmmeter to x1000 range and attach leads to each end of high tension wire.
2. Resistance should not exceed 25,000 ohms per wire. If it does, replace wires.

IGNITION WIRE RESISTANCE

PICK-UP COIL RESISTANCE TEST

1. On Pickup, Van, and 4Runner, measure pick-up coil resistance at distributor connector. (Scheme 3)
2. If resistance is incorrect, remove ignition coil (if equipped) and replace distributor assembly.

PICK-UP COIL RESISTANCE - OHMS

Toyota Pick-Up Coil Resistance Test. Scheme 3

ENGINE CRANKES BUT WILL NOT START

Check for faulty spark plug(s), ignition coil, ignition module, distributor and ignition system wiring. Repair or replace parts as necessary. Check ignition timing and adjust if necessary.

HESITATION & POOR ACCELERATION

Check for faulty spark plug(s) and ignition system wiring. Repair or replace parts as necessary. Check ignition timing and adjust if necessary.

ROUGH IDLE, STALLS

Check for faulty spark plug(s), ignition coil, ignition module, distributor, and ignition system wiring. Repair or replace parts as necessary. Check ignition timing and adjust if necessary.

Exploded View of Toyota Distributor. Scheme 4

Note. Distributors on Pickup and 4Runner 22R-E engines are not serviceable and must be replaced as an assembly.

REASSEMBLY

Note. Reassembly information not available from manufacturer.

See also:
• IGNITION COIL RESISTANCE TESTS