How To Test The Ignition System (1993-1998 5.2L Grand Cherokee)

TEST 6: Testing The Ignition Coil's Activation Signal

The ignition coil gets an activation signal from your 5.2L V8 Jeep Grand Cherokee's fuel injection computer.

On the 1993-1998 5.2L V8 Jeep Grand Cherokee, the wire that delivers the activation signal to the ignition coil is the gray with white stripe (GRY/WHT) wire of the connector.

To test the presence of this signal (while we crank the engine), we're gonna' use a 12 Volt automotive test light.

Let's get started:

1. 1

   Connect the alligator clip of the 12 Volt test light to the battery positive (+) terminal.

2. 2

   Touch the ignition coil's terminal labeled with the number 1 with the tip of your 12 Volt test light's metal probe.
   
   IMPORTANT: Gently probe the front of the female terminal with the 12 Volt test light to avoid damaging it.

3. 3

   Have an assistant crank the engine while you maintain the 12 Volt test light's probe touching the terminal.

4. 4

   The 12 Volt test light should blink on and off the whole time the engine is being cranked.
   
   NOTE: Don't worry about what the 12 Volt test light does before or after your helper starts cranking the engine. The only results you're interested in interpreting are the results obtained with the engine cranking.

Let's examine your test result:

CASE 1: The 12 Volt test light flashed ON and OFF. This is the correct test result.

With this test result you can conclude that your 5.2L V8 Jeep Grand Cherokee's ignition coil is bad only if you have confirmed that:

• All 8 spark plug wires are not sparking (TEST 1).
• The ignition coil's high tension wire does not spark (TEST 3).
• The ignition coil's tower does not spark (TEST 4).
• The ignition coil is getting 10 to 12 Volts (TEST 5).
• The ignition coil is getting an activation signal (TEST 6).

Here's why: If the ignition coil is getting 10 to 12 Volts (TEST 5) and it's getting an activation signal (TEST 6) then it has to spark. Since your test result confirms that it does not spark, you can conclude that the ignition coil is defective.

To solve the no-start problem on your 5.2L V8 Jeep Grand Cherokee, replace the ignition coil.

CASE 2: The 12 Volt test light DID NOT flash ON and OFF. This tells you that the ignition coil is not getting an activation signal and without it the ignition coil will not spark.

Re-check all of your connections and repeat the test. If the 12 Volt test light does not flash on and off then the most likely cause of this missing signal is a bad crankshaft position sensor or a bad camshaft position sensor (distributor pickup coil).

The following tutorials will help you test the crankshaft and camshaft position sensors on the 1993-1998 5.2L V8 Jeep Grand Cherokee:

• How To Test The Camshaft Position Sensor (1993-1997 5.2L Grand Cherokee).
• How To Test The Crankshaft Position Sensor (1993-1996 5.2L Grand Cherokee).

Other Causes Of A Misfire

Quite a few things can cause a misfire problem that are not ignition system failure related. So if you tested the ignition system, with the help of this tutorial, and found no problems, then the following suggestions may help:

1. Check the spark plugs.
   • Check that none have broken porcelain insulators. Especially if you've recently done a tune-up and dropped one on the floor.
   • You power washed the engine (this is something that you should probably avoid doing in any electronic fuel injected vehicle).
2. Check for carbon tracks on the spark plugs.
   • Check to see if carbon tracks have formed on the spark plug's porcelain insulator. The photo above shows what a carbon track looks like on the inside of the spark plug wire boot and on the ceramic insulator of the spark plug.
3. Check engine compression.
   • One of the most overlooked diagnostic tests to find the root cause of misfire is the compression test.
   • You can find the engine compression test explained here: How To Do An Engine Compression Test (1993-1998 5.2L Jeep Grand Cherokee).

Where To Buy The Distributor Cap, Distributor Rotor, Spark Plug Wires And Save

The following links will help you to comparison shop and hopefully save you a few bucks on its purchase:

NOTE: The distributor cap, the distributor rotor, and the spark plug wires fit the following vehicles: 1993-1998 5.2L V8 Jeep Grand Cherokee.

More 5.2L Jeep Grand Cherokee Tutorials

You can find a complete list of 5.2L Jeep Grand Cherokee tutorials in this index:

• Jeep 5.2L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Do An Engine Compression Test (1993-1998 5.2L Jeep Grand Cherokee).
• How To Test A Blown Head Gasket (1993-1998 5.2L Grand Cherokee).
• How To Test The MAP Sensor (1993-1996 5.2L Grand Cherokee).
• Ignition System Wiring Diagram (1996-1998 5.2L Jeep Grand Cherokee).