TEST 3: Testing For Spark Directly On The Coil Tower (Paired Cylinders)
You've been directed here because you got a no-spark result from two spark plug wires that feed spark to cylinders 1 and 5, or cylinders 3 and 4 or cylinders 2 and 6.
As mentioned before, this usually indicates that one of the 3 ignition coils inside the coil pack is bad.
To make sure, the next step is to test for spark directly on the ignition coil pack towers that feed those two spark plug wires (that did not fire off spark in TEST 1).
This will also make sure that the spark plug wires are not to blame for this missing spark.
You'll test one coil tower at a time and this is what you need to do:
Remove the spark plug wire that did not fire off spark from the ignition coil pack.
Place the spark tester directly on the ignition coil tower, in place of the spark plug wire you just removed (see photo above).
Connect the spark tester to the battery negative (-) post with a battery jump start cable.
Have your helper crank the engine.
CAUTION: The vehicle may or may not start, either way be careful!
You're gonna' get one of two results: Spark or no spark.
Repeat steps 1 thru' 5 (of this same test) on the other coil pack tower whose spark plug cable did not fire off spark.
Let's take a look at what your test result means:
CASE 1: You got spark from both coil pack towers. This is the correct test result and it confirms that the ignition coil is good. It also condemns the spark plug wire as bad. Replace all of the spark plug wires as a set.
Replacing the spark plug wires (as a set) will solve the misfire condition and the misfire code lighting up the check engine light (CEL) on the instrument cluster.
CASE 2: You got spark from only one coil pack tower. This result confirms that the ignition coil is bad. Replacing the ignition coil pack will solve the misfire condition and the misfire code lighting up the check engine light (CEL) on the instrument cluster.
CASE 3: You got NO spark from both coil pack towers. Then the next step is to verify that the PCM or ignition module is generating and feeding a switching signal to the individual ignition coil within the coil pack (that feed spark to the two towers you just tested).
Choose from one of the following:
- If those coil pack towers feed cylinders 1 and 5, go to: TEST 5: Switching Signal Cylinders 1 And 5.
- If those coil pack towers feed cylinders 2 and 6, go to: TEST 6: Switching Signal Cylinders 2 And 6.
- If those coil pack towers feed cylinders 3 and 4, go to: TEST 7: Switching Signal Cylinders 3 And 4.
TEST 4: Testing The Power (12 Volts) Circuit
This test step can be accomplished using either a multimeter or a test light.
NOTE: Avoid probing the female terminals of the connector, or you run the risk of damaging them. The consequences of probing the front of the connector with the test light or multimeter leads are that (1) the female terminal will open up to whatever size the tip of the test light is and (2) this will cause and intermittent loss of power because this now opened up terminal will not make a good and solid contact with the male spade terminal on the coil pack.
OK, when doing the test itself, you're gonna' test for this voltage with the key ON and the engine OFF and then with the key ON and engine cranking.
OK, let's start:
Disconnect the ignition coil pack from its electrical connector.
Set your multimeter to Volts DC mode.
Probe the wire that connects to the male terminal labeled with the number 4 (in the illustration above) with the red multimeter test lead and an appropriate tool.
Connect the black multimeter test lead to the battery negative (-) post.
Have your assistant turn the key to the RUN position and then have him (or her) crank the engine.
Your multimeter should register 10 to 12 Volts DC.
Let's take a look at your test result:
CASE 1: The multimeter registered 10 to 12 Volts. This result lets you know that the coil pack is receiving power and that the power circuit requires no further testing.
If your Ford (or Mercury) car or truck still has NO SPARK coming out of any of the spark plug wires, this could possibly due to one of three things:
- Bad spark plug wires.
- Bad coil pack.
- PCM (Powertrain Control Module=Fuel Injection Computer) is not providing any of the Switching signals to the individual ignition coils within the coil pack because the crankshaft position sensor has failed.
- For some of the applications covered by this article, you can find the crank sensor test here: How To Test The Crank Sensor (Ford 3.0L, 3.8L) (at: troubleshootmyvehicle.com).
You're starting point for the rest of your tests will be TEST 3. IMPORTANT: Altho' TEST 3 indicates it's a test for when two spark plug wires didn't fire spark only, this is still your starting point.
CASE 2: The multimeter DID NOT register 10 to 12 Volts. Then the most likely cause will be a blown fuse or a bad relay. You'll have to consult your repair manual to find out the location of this fuse and or relay.
Even tho' testing the entire power circuit is beyond the scope of this article, since this article only deals with testing the Ford coil pack, you have now eliminated the coil pack itself as the cause of the 'no-start no-spark' condition.