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    Main Relay   Ignition      

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 Ignition system DO IT YOURSELF 

How it works
How to spot bad ignition circuit - In 1 minute
You ride along in your Acura or Honda when suddenly your car cuts out. As you lose momentum your car rolls a few feet to a stop . Friends and strangers help push your car along. You've just experience what most likley is an an ignition fault. A simple block diagram shows you why your car may have stopped. The battery takes it's path from the ignition switch to the computer, igniter and coil.
(point mouse over picture)

The ECU tells the Igniter when to switch the coil OFF.

The next step is to check for sparks. Remove one end of the plug wire. Insert a spark plug into the wire. Lay the plug solid end to a suitable ground. E.g. exposed bolt, nut, etc.

Warning: Coil shock may be hazardous due to abrupt body movement causing injury. Practical step is to isolate you from ground - Do not lean on metal body panels, plastic bumpers okay. DO NOT ATTEMPT on a distributerless ignition system - with lethal voltages up to 70KV. Next step is to check for spark at the coil. Connect the plug boot on the right of the picture directly to the output (secondary) of the coil with a help of a wire to close the gap, if needed. Make sure it closes.

My problem sounds like a main relay. Check for fuel. Listen to the fuel pump. Listen to the second click when ignition is first turn on. The second click will coincide with the disappearing "check engine light."


Could it be something else. Open the oil cap to see if the rocker arms are moving. If not, you will need to deal with your tming belt first.

Educational lesson: An igniter recieves square wave signals ( in mA) sent from the ECU, determines the rate of the signal and compares it to a reference (the dwell time) which tells it how long to charge the coil. When the signal goes to ground the igniter cuts off power to the coil to produce spark. In other words, it's an itegrated time management circuit combined with a transistor. On previous generation the reluctor gives the signal to the igniter.

To spot a bad igniter :

1. The tachometer quits abruptly or jerks around before stalling.
2. No spark at the coil.
3. No on/off voltage at the coil's (+, - ) terminals when cranking.


The distriutor rotor spins inside the distributor delivering spark to each plug wire in a timely manner. Should it fail there will be no spark at the plugs, however, you will see spark at the coil. Check for spark . To spot a bad rotor :

1. The distributor is hot to the touch.
2. No spark at the plug wires.
3. Spark is found at the coil.
4. A cricket noise is heard from the distributor before stalling.


To spot a bad ignition switch :

1. Car stalls then retarts, then stalls after driving.
2. Car runs fine when key slightly held at start position.
3. No battery + voltage at the coil + positive terminal.

Ignition Switch

To spot a bad coil :

1. The distributor was disturbed before it died.
2. No spark at the plug wires.
3. No spark at the coil's output (secondary.)



Making test jigs are simple. You will need :

1. Two aligator clips.
2. LED, 1-W Bulb.
350 to 999-Ohm resistor.
4. Two wire leads.


To spot a bad ignition switch probe pins 3 with the top LED jig and pin 2 with the bottom BULB jig: Warning: DO NOT BE CONFUSED. Probing pin three with the bulb jig (bottom jig) may harm the coponent in circuit. The igniter may be designed for 100 mA max or input voltages of -0.3 to + 0.3. The LED jig has a low impedance. Use the LED jig for all circuit tests before investigating further.

Step 1. Clip the positve end of the LED probe to the battery positve terminal.
Step 2. Clip the LED probe pin 3. Crank the engine (assuming no spark) at the plug wires.
Step 3. Do you see blinking? No- ECU is bad, check for ECU codes. Yes-Coil/igniter is bad go to step 4.
Step 4. Connect the BULB probe tip to - negative terminal of the coil, it may be labled [-].
Step 5. Do you see blinking? No - Igniter bad, replace it. Yes - Coil bad replace it.
Coil spark checked.

Terminals colors for 90-93 Accords

1. Blue for most Hondas/Acuras.
2. Blu2, Blu1 is for tach with in series resistor.
3. Blk/Yel.
4. Yelow green (Do not test with a test lamp.)

Terminals colors for 86-89 Accords if applicable.

1. Blue.
2. Lt/Grn but, at coil end Blk/Wht.
3. Blk/Yel.
4. Not used. The reluctor is tied directly to igniter.

CAUTION: Always ground the high-voltage port on the coil whendoing electrical tests and cranking. The igniter or coil may destroy itself by finding another short path to ground. Shorting the high voltage port out won't harm the coil.

Related helpful links
 Honda FAQ relay
Rover Ignition
Mark's Site

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