TEST 4: Testing The Power (12 Volts) Circuit
In this test section, we're gonna make sure that the ignition coil pack is getting power (which is in the form of 10 to 12 Volts).
The terminal of the connector that delivers these 10 to 12 Vols is the one I've labeled with the number 2 in the illustration above.
NOTE: Be careful when probing the front of the terminal with your multimeter test leads, or you could damage it (and then you'll need to replace the entire connector).
Let's start:
- 1
Disconnect the ignition coil from its connector.
- 2
Put the multimeter in Volts DC mode.
- 3
Connect the black multimeter test lead to the battery negative (-) terminal.
- 4
Gently probe the front of the female terminal labeled with the number 2 with the red multimeter test lead (using an appropriate tool).
- 5
Have your helper turn the key to the ON position.
- 6
You should see 10-12 Volts on your multimeter.
Let's find out what your test result means:
CASE 1: The multimeter registered 10 to 12 Volts DC. This is the correct test result.
Then the next step is verify that the ignition coil (IC) activation signals are present, go to: TEST 5: Activation Signal For Cylinders 1 And 4 and then perform TEST 6: Activation Signal For Cylinders 2 And 3.
If the both IC activation signals are not present (after testing them in TEST 5 and TEST 6), the most likely cause is a bad crankshaft position sensor.
CASE 2: The multimeter DID NOT register 10 to 12 Volts DC. Re-check all of your connections and retest.
If still no voltage is present, this result exonerates the coil pack. Repairing the cause of this missing voltage will solve the 'no-spark no-start' condition of your Ford Fiesta.
TEST 5: Activation Signal For Cylinders 1 And 4
In this test step, you're going to verify that the ignition coil (within the coil pack) that fires spark to cylinders 1 and 4 is being supplied with an activation signal.
We're gonna use an automotive 12 Volt LED light to check for this activation signal.
CAUTION: The terminals of the LED need to be inserted into the female terminals of the ignition coil's connector. The LED light's terminals cannot be thicker than the ignition coil's male spade terminals that mate into the connector's female terminals. You may need to modify the terminals of the LED light so that they match the width and thickness of the ignition coil's male spade terminals, to avoid damaging them.
Alright, let's start:
- 1
Disconnect the ignition coil from its 3-wire electrical connector.
- 2
Connect the red lead of the LED light to terminal number 2.
Terminal number 2 is the terminal that supplies power to the ignition coil. - 3
Connect the black lead of the LED light to the terminal identified with the number 3 (see illustration above).
Terminal 3 should connect to the yellow with grey stripe (YEL/GRY) wire of the ignition coil's 3-wire connector. - 4
Have your helper crank the engine.
- 5
The LED light should flash ON and OFF the whole time the engine is cranking.
Let's find out what your test result means:
CASE 1: The LED light flashed ON and OFF the whole time the engine was cranking. With this test result you can conclude that the PCM is providing the Switching signal and the circuit is OK.
You can conclude that the ignition coil pack is bad if you have:
- Confirmed that the spark plug wires for cylinders 1 and 4 are not sparking (TEST 1).
- Confirmed that the ignition coil towers for cylinders 1 and 4 are not sparking (TEST 3).
- Confirmed that the ignition coil pack is receiving the 1/4 activation signal from the fuel injection computer in this test section.
CASE 2: The LED Light DID NOT flash ON and OFF the whole time the engine was cranking. This test result usually means that there's either an open-circuit in the circuit between the connector and the PCM or the PCM is fried (altho' a fried PCM is rare).
With this result you have eliminated the coil pack itself as the source of the misfire condition or no-spark condition.
