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How to Test the Ford TFI Ignition System

Whether your Ford or Mercury car or truck CRANKS but DOES NOT START or runs with a MISFIRE Condition, this article is for you. With the tests you'll be able to pinpoint the problem to the Ignition Control Module or the Ignition Coil or the Profile Ignition Pickup Sensor (PIP Sensor) or the Spark Plug Wires or the Distributor Cap.

This article applies to both the Gray colored Ignition Control Module and the Black colored Ignition Control Module. The Gray colored Ignition Control Module is called the Push Start Module and the Black colored Ignition Control Module is called the Computer Controlled Dwell Module. These Ignition Control Modules (ICM) are not interchangeable but are tested in the exact same way. Also, the photos (in the image viewer) show some of the tests performed on a V8 engine. This might make you think that they don’t apply to your 3.0L, 3.8L V6... well nothing could be further from the truth. All of these test steps apply to both the V8, V6 and L6 Ford engines.

As you can see from the image of the Ignition Control Module (in the image viewer on the left), the tests apply to the fender mounted Ford Ignition Control Module.

How Does this Type of Ignition Control Module Work?

Here's a little background information to help you diagnose this no spark condition. In a nutshell, when the system is working properly and you turn the key to crank and start your Ford car or truck:

1. The Distributor shaft starts to rotate which causes the PIP (Profile Ignition Pickup) Sensor to start generating its Crankshaft Position Signal.

2. The Ignition Control Module (ICM), upon receiving this PIP Signal, starts to 'open and close' the Ignition Coil's primary current. As you might already be aware, it's this action that makes the Ignition Coil Spark.

3. The Fuel Injection Computer also receives the PIP Signal at the same time that the Ignition Module does.

4. Once the engine STARTS, the Fuel Injection Computer takes over the Ignition Timing

The PIP Sensor is at the heart of this Fender Mounted Ignition Control Module and Ignition System. Here are some useful facts that you should be aware of about the PIP (Profile Ignition Pickup) Sensor:

1. The PIP Sensor is located in the Distributor.

2. It's a Hall Effect type Sensor.

3. It produces a digital square wave if its Signal is tested on an Oscilloscope.

This signal can also be tested with an LED Light (which is the method I'll use in this article). Do not substitute a regular 12 volt lamp (Test Light) where ever a FAST TEST article calls for this LED test tool!

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4. If it goes BAD, the your Ford car or truck will CRANK but NOT START.

What Tools do I need for the Ignition Module Test?

No expensive tools are required to test this type of Ignition System. Now, having said that, there some very specific tools that I recommend to use for the tests. So, here's the basic list:

1. A Spark Tester

a. Not just any type of Spark Tester. I strongly suggest you buy the HEI Spark Tester.

b. Don't use a regular Spark Plug instead of a dedicated Spark Tester.

c. Don't pull the Spark Plug Wire off of the Spark Plug as the engine is cranking or running. This will give a false result and/or damage the Ignition Coil.

2. An LED Light.

3. Multimeter.

4. Repair Manual.

5. Helper or remote starter hand switch.

By the way, you don't need an Automotive Scan Tool for any of these tests.

Where Do We Start?

The very first thing we'll do is test for Spark. Then we'll the basics like Battery voltage and Engine Ground to the Ignition Control Module. Then we'll test the Ignition Coil Switching Signal that the Module generates in action and from the results you get you'll be able to pinpoint the problem to the Ignition Control Module (ICM) or the Ignition Coil or the Profile Ignition Pickup (PIP) Sensor or the Spark Plug Wires or the Distributor Cap or completely eliminate these as the cause of the No Start Condition.

IMPORTANT- All of the tests are ON CAR TESTS, do not remove the Ignition Control Module Assembly from the vehicle (all of the figures show the Module Assembly off of the vehicle but this is just for illustration purposes only). Also, the Battery must be in a fully charged condition for all tests in this article.

Here are brief descriptions of the circuits that we'll be testing. You'll notice that there are no wire color descriptions. This is intentional. The color of the wires in the illustration will not match the ones on your vehicle. The good news is that no matter what color the wires are (on the vehicle), the circuit descriptions DO NOT CHANGE. You will be able to successfully diagnose this NO START CONDITION with this information.

IMPORTANT- It will be necessary to test some of these circuits while the engine is being cranked. Be careful, use common sense and take all necessary safety precautions.

Ignition Control Module Connector

1. Circuit 1

1. Ground.

2. Circuit 2

1. Ignition Coil Switching Signal. This is the circuit that the Ignition Control Module (ICM) uses to interrupt the Primary Current flowing thru' the Ignition Coil. This action is what causes the Ign. Coil to fire off Spark.

3. Circuit 3

1. Power (12 V) with key on.

4. Circuit 4

1. START or IDM circuit. This is the circuit that the Fuel Injection Computer uses to control Ignition Timing in conjunction with the SPOUT Signal.

5. Circuit 5

1. SPOUT input. This is the circuit that the Fuel Injection Computer uses to control Ignition Timing in conjunction with the START or IDM Signals.

6. Circuit 6

1. PIP input (Profile Ignition Pickup Sensor Signal). This is the Signal that both the Ignition Module and Fuel Injection Computer use to know the piston positions to start fuel injection and spark, rpm's, etc.

IMPORTANT- The module could be located on the left or right inner fender in the engine compartment. This could confuse you as to which wire is the #1 circuit. The rule of thumb is to take the first mounting bolt (see the BLUE ARROW on the figure above) nearest to the connector as a point of reference.

TEST 1: Testing for Spark

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Just a friendly reminder... do not use a regular Spark Plug in place of a Spark Tester for the Spark Test and PLEASE do not pull the Spark Plug Wire off of the Spark Plug either while the engine is cranking (to check for Spark). Ok, let's start:

1. Remove the Spark Plug Wire from its Spark Plug.

2. Attach the HEI Spark Tester (or an equivalent Spark Tester) to the Spark Plug Wire.

3. Attach the HEI Spark Tester to a good Ground point, or use a Battery Jump Start Cable to attach it to ground (my preferred method).

4. Have your helper crank the engine while you observe the Spark Tester.

5. Repeat the test for all of the remaining Spark Plug Wires.

If you got Spark on all of the Spark Plug Wires: This result indicates that the Spark Plug Wires, Distributor Cap and Rotor, Ignition Module, and Ignition Coil are working. You have eliminated these as the cause of your NO START Condition.

If you got NO Spark on none of the Spark Plug Wires: This result doesn't condemn any specific component just yet. The next step is to remove the Spark Plug Wire that attaches to the middle tower of the Distributor Cap (this is the Spark Plug Wire that comes from the Ignition Coil) to test for Spark there. This test will directly test the Ignition Coil itself and thus eliminate the Distributor Cap as a possible source of the No Spark result. Go to Test 3.

If you got Spark on some but not all of the Spark Plug Wires: More than likely the Spark Plug Wires are BAD or the Distributor Cap is BAD. It's a common problem for one or two Spark Plug Wires to go bad or for one or two Distributor Cap towers to go BAD and not let Spark thru'. 90% of the time replacing the Distributor Cap, the Distributor Rotor and the Spark Plug Wires should solve your problem, BUT to further test this, go to TEST 2.

TEST 2: Testing for Spark at the Distributor Cap

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Important: this test is only for when one or several (but not all) of the Spark Plug Wires did not Spark!

1. OK, remove the Spark Plug Wire that did not Spark from its tower on the Distributor Cap and place the Spark Tester directly on the tower. I recommend you use a Battery Jump Start Cable to hold the Spark Tester to the tower as shown in the photo at left. Also, you MUST use a small piece of vacuum hose to attach the HEI Spark Tester to the Cap tower being tested.

2. Have your assistant crank the engine while you observe the Spark Tester.

3. Repeat this test with the others that did not fire off Spark (if applicable).

If you got Spark, Then the Spark Plug Wire is BAD, replace them all. This is probably as far as you may need to go since your Ford car (or truck, or mini-van, or van) will probably start or solve your misfire problem after replacing these parts.

Here's why: As the Spark Plug Wire ages, its normal resistance to spark increases to the point that the Wire can not and does not transmit the Spark to the Spark Plug. This will either cause a Misfire, or a lack of power, or a No Start Condition. Spark Plug Wires don't last forever, especially after-market ones (average life-span is 3 to 4 years).

If you got No Spark, Then the Distributor Cap is BAD. Replace the Distributor Cap and Distributor Rotor as a Set. This should solve your misfire problem.

Here's why: As the Distributor Cap ages, the terminals that transmit the Spark to the Spark Plug Wires corrode. This corrosion increases the resistance to Spark and over time (as more corrosion is created) this same corrosion stops the Spark from passing thru' to the Spark Plug Wires.

TEST 3: Testing for Spark at the Ignition Coil (Part 1)

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OK, with this test you're going to find out if the Spark Plug Wire that feeds the Spark from the Ignition Coil to the Distributor is BAD.

1. Remove the Spark Plug Wire that is attached to the center of the Distributor Cap and attach the HEI Spark Tester to this wire. The other end of this Spark Plug Wire must remain attached to the Ignition Coil (this is important!, look at the photo to see how I've done it).

2. With the HEI Spark Tester being held with a Battery Jump Start Cable (who's other end is grounded on the engine or Battery Negative Post), ask your helper to crank the engine once again while you watch for Spark jumping across the air gap of the Spark Tester.

If you got Spark, This result confirms that Spark is being delivered to the Distributor but that the Distributor Cap is unable to distribute the Spark to the Spark Plug Wires. Also, this test confirms that the Ignition Coil is GOOD. Replace the Distributor Cap and Rotor as a set and retest (or crank up the vehicle). This should solve your No Start Condition.

If you got NO Spark. Then further testing is required to see if the problem is due to a BAD Ignition Control Module (ICM), BAD Ignition Coil, BAD Pick Up Coil or something else. We're going to find out with the rest of the tests, Go To TEST 4.

TEST 4: Testing the Ignition Coil (Part 2)

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Now, you're going to test to see if the Ignition Coil has fried.

1. Remove the Spark Plug Wire that's attached to the Ignition Coil's tower (as shown in the photo on the left).

2. Now, connect the HEI Spark Tester to the Coil's tower with a small piece of Vacuum Tubing (this is important!, look at the photo to see how I've done it).

3. With the HEI Spark Tester being held in place on the Coil with a Battery Jump Start Cable (who's other end is grounded on the engine or Battery Negative Post), ask your helper to crank the engine once again while you watch for Spark jumping across the air gap of the Spark Tester.

You're going to get one of the 2 results: (1) Spark or (2) No Spark. Let's analyze each result in more detail below:

If you got Spark, then the Spark Plug Wire that feeds the Distributor Cap Spark is BAD and the Ignition Coil is GOOD. Replace the Spark Plug Wire by replacing All of the Spark Plug Wires.

Here's why: As the Spark Plug Wire ages, its normal resistance to spark increases to the point that the Wire can not and does not transmit the Spark to the Spark Plug. This will either cause a Misfire, or a lack of power, or a No Start Condition. Spark Plug Wires don't last forever, especially after-market ones (average life-span is 3 to 4 years)

If you got NO Spark. Then further testing is required to see if the problem is due to a BAD Ignition Control Module (ICM), BAD Pick Up Coil or something else. We're gonna' find out with the rest of the tests, Go To TEST 5.

TEST 5: Testing the Ignition Coil for 12 Volts

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For this test you can use a Multimeter or a Test Light. Also, altho' you're testing the Ignition Coil for 12 Volts, you're indirectly testing the Ignition Control Module (ICM) and the PIP (Profile Ignition Pickup) Sensor for 12 Volts also... since the same Power Circuit feeds them all.

The procedure I recommend to use (to accomplish all of the tests below) is to use a test probe that pierces thru' the wire's insulation. I don’t recommend inserting anything into the front of the female terminal. Whatever method you use, the key here is not to damage the female terminal or the wire. Again, be careful. Use common sense and take all necessary safety precautions.

1. The Ignition Coil must be connected to its connector.

2. Put the multimeter in VOLTS DC mode.

3. With a Wire Piercing Probe (or something appropriate) probe the left wire (the one on the driver's side of the Ignition Coil Connector- see photo in the image viewer). The 'left side' in automotive speak always refers to anything on the driver side.

a. Or you can probe the circuit labeled with the number 3 (see 2nd photo in the image viewer) of the Ignition Control Module.

b. Both wires are part of the same circuit, so it doesn't matter which of the two you probe, both will give you the same test result.

4. With the BLACK lead of the multimeter probe the BATT (-) NEGATIVE terminal.

5. Turn Key On with the Engine Off.

If you got 12 Volts, all is good in the neighborhood, the next step is to check to see if the Ignition Coil is receiving the Switching Signal from the Ignition Module...GO TO TEST 6.

If you DID NOT GET 12 Volts, you must find out why you're missing this voltage. Without this Voltage the Ignition Control Module nor the Ignition Coil will work. Resolving this Power issue should solve your No Start Condition.

TEST 6: Verifying the Ignition Coil's Switching Signal[pic]

In this test you're going to verify that the Ignition Control Module (ICM) is activating the Ignition Coil by verifying that the Switching Signal is present. You're going to use a Test Light. This test is performed with the engine being cranked, so be careful and take all necessary safety precautions.

1. This test is performed with the Ignition Coil Connector connected.

2. Insert the metal probe end of the Test Light to the rear of the connector to back-probe the terminal on the right side of the Ignition Coil Connector (look at the photo in the image viewer). The 'right side' in automotive speak always refers to anything on the passenger side.

a. Or you can probe the circuit labeled with the number 2 (see 2nd photo in the image viewer) of the Ignition Control Module.

b. Both wires are part of the same circuit, so it doesn't matter which of the two you probe, both will give you the same test result.

3. Connect alligator clip end of the Test Light to the Battery (+) Positive terminal. It is IMPORTANT that it be connected at the Battery Positive Terminal.

4. Have an assistant crank the engine.

If the Test Light flashed On and Off, then the Ignition Coil is BAD, replace it. This also means that the Ignition Control Module (ICM) and Pick Up Coil are GOOD. Replacing the Ignition Coil will solve your No Spark/No Start Condition.

If the Test Light DID NOT flash On and Off, re-check all of your connections and retry the test again. If the Test Light still does not flash on and off, GO TO TEST 7.

TEST 7: Testing the Profile Ignition Pickup (PIP) Signal

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Here we'll check that the Profile Ignition Pickup (PIP) Sensor is being received by the Ignition Control Module (ICM). This will be achieved by using an LED test tool. Do not use a Test Light in lieu of an LED Light.

1. With key in the OFF position.

2. With a suitable tool, pierce the number 6 circuit wire of the Ignition Control Module Connector.

3. Connect the BLACK wire of LED to the tool that is piercing the wire.

4. Connect the RED wire of the LED to the BATTERY (+) POSITIVE terminal.

5. Have an assistant crank the engine while you observe the LED.

The LED should start to blink on and off as the engine is cranked. Is the LED blinking on and off as the engine is cranked? (Oscilloscope Users see picture of Wave Form)

If the LED light flashed on and off the whole time the engine was being cranked, then the PIP (Profile Ignition Pickup) Sensor is creating and sending its signal. This result indicates that the Ignition Control Module is BAD and the cause of the NO SPARK and CRANKS but DOES NOT START Condition. Replace the Ignition Control Module (ICM).

If the LED Light DID NOT flash on and off the whole time the engine was being cranked, then the PIP (Profile Ignition Pickup) Sensor is BAD and is the cause of the NO SPARK and CRANKS but DOES NOT START Condition. Replace the PIP Sensor in the Distributor.

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