Spark Test

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Is your engine failing to start because there is no spark? Or you wonder if it is getting spark? Test your engine's ignition system.

Coil Test

Does coil have proper voltage feed?

1. Turn KEY the ON
2. Measure the voltage at the coil. It should be either 6v or 12v. If you have electronic ignition fitted (with no ballast resistor), it should be 12V (same as battery). If less, the problem is in the hot feed (battery, fuse, ignition switch or wiring)

Does coil spark?

1. If the supply voltage is correct, turn key OFF. Disconnect all '-' wires from coil.
2. Connect a length of test wire to the NEG battery post
3. Remove coil spark wire (high tension lead) from the distributor cap, and place the end within 1/4" of a strut tower bare bolt
4. Turn KEY the ON
5. Touch the NEG test wire to the coil '-' terminal (a small spark with occur where you touch it) and hold for a 1/3 second. Then remove the wire. A weak spark at the wire should occur on removal.

NOTE: This will work only one time, so 
watch carefully.

If there is a spark, the coil and coil spark wire are OK. If there is no spark or only a weak yellow spark, the problem could be the spark wire, or the coil.

Spark Lead Test

Test the coil spark wire. 
See Spark Plug Wires#Inspection

Coil Electrical Test

The Datsun 1200 factory service manual has these specifications for the stock coil:

Primary resistance: 1.17 to 1.43 ohms @ 20C/68F
Secondary resistance: 11.2 to 16.8 ohms @ 20C/68F
External Resistor: 1.3 to 1.7 ohms @ 20C/68F

Use an ohmmeter to test it:

1. Ignition key OFF
2. Coil wires removed from coil. Coil spark wire removed
3. Connect ohmmeter to center terminal metal and to Coil- terminal

   Results:

   • OK - 8200 to 12400 ohms
   • Not OK - anything else. Coil is bad.

4. Connect ohmmeter to Coil+ and to Coil- terminals. Put ohmmeter on x1 setting/range.

   Results:

• 1. OK - 0.84 to 1.02 ohms
  2. Not OK - other reading. replace coil.

If you are using some other coil, check the factory service manual or coil manufacturers instructions.

Electronic Ignition Coil

Nissan factory service manual says about checking the coil (matchbox coil):

1. Ignition key OFF
2. Coil wires removed from coil. Coil spark wire removed
3. Connect ohmmeter to center terminal metal and to Coil- terminal
   • OK - 8200 to 12400 ohms
   • Not OK - anything else. Coil is bad.
4. Connect ohmmeter to Coil+ and to Coil- terminals. Put ohmmeter on x1 setting/range.
   • OK - 0.84 to 1.02 ohms
   • Not OK - other reading. replace coil.

Basic Spark Test

1. Disconnect a spark plug lead (spark plug wire) and position the terminal within 6 mm (1/4 inch) of bare metal. For example a nut on the strut tower. It may be necessary on leads fitted with terminal insulation to use a piece of wire, a split pin or screwdriver as an extension to the terminal.

   

2. Have an assistant turn the key to START and crank the engine a few seconds
3. Check that the spark, if any, jumps the gap to the metal. If there is no spark or the spark is weak or yellow, carry on with next step. If the spark is satisfactory skip the next step.
4. Disconnect the coil lead (coil spark wire) from the distributor cap and repeat the test previously described for the spark plug lead in points (1) to (3). If there is a strong blue spark then the fault lies within the distributor. Should there be no spark or a weak and yellow spark on both or either of the tests, then carry out the following action.

1. Check the spark plug leads to ensure that they are perfectly dry and that the insulation is not cracked.
2. Check the distributor cap to ensure that it is dry and clean. Examine both inside and outside of the cap for cracks or tracking, particularly between the spark plug segments in the cap.
3. Check the rotor arm for cracks, deposits or burning on the metal arm.
4. Ensure that the spark plug leads and the coil lead have dry, clean and secure connections in the distributor cap.
5. Check that the wires to the ignition switch side of the coil and from the contact breaker side of the coil to the distributor are intact and have clean secure connections.
6. Check that the carbon brush in the centre of the distributor cap interior face is clean and dry and ensure that it moves freely in and out of the locating hole.
7. Check that low tension current is reaching the ignition coil when the ignition is switched 'ON' by using a test lamp between the coil low tension terminals and a good earth. Ensure that the breaker points are open or insulated when making the test. Should the test lamp light on the ignition switch side of the coil but fail to light on the contact breaker side of the coil then it is possible that the coil primary circuit is faulty. Remove and test the coil or replace it with a known serviceable unit.

   NOTE: If a test lamp is unavailable the low tension lead can be disconnected from the ignition switch side of the coil and 'flashed' to a good earth in order to check for current flow. Similarly the other low tension lead can be disconnected at the distributor and 'flashed' to some other good earth to check for current flow. Ensure that the ignition switch is in the 'ON' position.

8. Check and if necessary clean and adjust the contact breaker points. See the appropriate heading in the Engine Tune-up section.
9. Ensure that the distributor low tension leads and the earth wire are intact, clean and secure.

Again carry out the check procedure. Should there still be no spark or a weak and yellow spark, then one or more of the following faults may be the cause:

• Defective coil, capacitor or high tension leads. If the contact breaker points showed severe burning or pitting of the point faces in the previous check then this would indicate a possible capacitor failure. Renew the capacitor and contact breaker points.

If the above checks prove the spark to be satisfactory but the engine still fails to start, remove all the spark plugs and check their condition and electrode gap.