When the ignition coil fails and stops firing spark, your Corolla's engine is gonna crank but not start. Thankfully, checking if the ignition coil is good or bad isn't difficult at all.
In this tutorial, I'm gonna walk you through my ignition coil test procedure step by step. By the end, your test results will tell you if the coil's still good or if it's fried and needs replacing.
NOTE: The ignition coil test procedure is an on-car test. The pics show the distributor taken out just to make the test connections clearer. Don't remove the distributor from the engine for any part of this process.
Contents of this tutorial:
- Ignition Coil Basics.
- What Tools Do I Need To Test The Ignition System?
- Where To Buy The Ignition Coil And Save.
- TEST 1: Checking The Spark Plug Wires For Spark.
- TEST 2: Checking The Ignition Coil For Spark.
- TEST 3: Checking The Distributor Cap For Spark.
- TEST 4: Making Sure The Ignition Coil Is Getting Power.
- TEST 5: Making Sure The Ignition Coil Is Getting Its Activation Signal.
- More 1.8L Toyota Corolla Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- 1.8L (7A-FE) Toyota Corolla: 1993, 1994.
- 1.8L Geo Prizm: 1993, 1994.
Ignition System Wiring Diagrams:
Ignition System Tests:
- How To Test The Igniter (1993-1994 1.8L Toyota Corolla).
- How To Test The Distributor Pickup Coil (1993-1994 1.8L Toyota Corolla).
Engine No-Start Basics:
Ignition Coil Basics
The ignition coil's sole purpose is to step up 12 Volts to the high voltage needed to create the spark that jumps across the spark plug electrodes to ignite the air/fuel mix inside the cylinders.
Here's how it all works:
- Signals from the pickup coil: When you turn the key and crank the engine, the pickup coil inside the distributor sends out two signals —RPM (NE) and crankshaft position (G)— to the fuel injection computer.
- Igniter kicks in: Once the computer reads these signals, it sends an activation pulse to the igniter (also called the ignition control module).
- Ignition coil gets activated: The igniter then switches the ignition coil on and off.
- Ignition coil sparks: The ignition coil ramps up the 12V battery power into high voltage. At this stage, the high voltage isn't technically a spark yet. But for the sake of simplicity, I'll call it a "spark."
- Spark travels: That high voltage moves through the distributor cap, rotor, and spark plug wires (high tension wires), delivering it to the spark plugs.
- Fuel ignites: When the high voltage hits the spark plug, it jumps the electrodes' air gap, creates a spark, and lights up the air/fuel mix inside the cylinder.
- Engine runs: With all four cylinders igniting their air/fuel mixture, the engine fires up and runs.
The key to successfully diagnosing the ignition coil is knowing that it won't work unless it's getting both power from the battery and an activation signal from the igniter.
If either one is missing, the coil won't create the spark needed to start and keep the engine running.
What Tools Do I Need To Test The Ignition System?
You'll need three tools to test the ignition system on your 1993-1994 1.8L Toyota Corolla:
- Spark tester: This tool gives you an accurate spark test result. There are plenty to choose from, but I recommend the OTC HEI spark tester. You can check it out and buy it here: OTC 6589 Electronic Ignition Spark Tester (at: amazon.com).
- Multimeter: A multimeter helps confirm if the ignition coil's getting power (TEST 4). If you don't have one, here's the one I recommend: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter with NCV Feature, Mastech MS8268 Upgraded, MS88 (at: amazon.com).
- 12V automotive test light: This test light checks whether the ignition coil is getting its activation signal in TEST 5. If you need one, this is the one I use and recommend: Lisle 28400 Heavy Duty 12 Volt Test Light (at: amazon.com).
Where To Buy The Ignition Coil And Save
I'm recommending the Standard Motor Products UF204 Ignition Coil as the one you should purchase, since it's a well-known after-market brand. Once you get to amazon. Com thru the links below, you can also choose other brands too!
NOTE: Not sure if this ignition coil fits your Corolla? No worries! When you click the link and head to the site, they'll ask for your car's details to make sure it matches. If it doesn't, they'll help you find the right one.
TEST 1: Checking The Spark Plug Wires For Spark
To kick off our ignition coil diagnostic, we're gonna check for spark at each spark plug wire. This spark test will help us figure out if the engine's no-start problem is caused by a lack of spark.
For the most accurate results, use a dedicated spark tester. I suggest using the OTC 6589 Electronic Ignition Spark Tester —I use it myself, and it works perfectly straight out of the box. You can check it out and grab one here: OTC 6589 Electronic Ignition Spark Tester (at: amazon.com).
Alright, let's jump in:
- 1
Disconnect the spark plug wire from the #1 cylinder's spark plug.
- 2
Connect the spark tester to the spark plug wire.
- 3
Ground the spark tester straight to the battery's negative (-) terminal with a battery jump-start cable.
- 4
Have someone crank the engine while you keep an eye on the spark tester.
- 5
You'll get one of two results: Either you see a spark, or there's nothing.
- 6
Unplug the spark tester from the spark plug wire and reconnect the wire back onto its spark plug.
- 7
Repeat steps 1 to 6 on the other spark plug wires.
Let's break down what your test results tell you:
CASE 1: All four spark plug wires sparked. That's exactly what you wanna see —it means the ignition system isn't the reason your engine won't start.
You can cross these parts off the list of possible problems:
- The igniter (ignition control module).
- The ignition coil.
- The pickup coil inside the distributor.
- The distributor cap and rotor.
- The spark plug wires.
If the engine still refuses to start, the issue isn't with the ignition coil or anything in the ignition system.
CASE 2: Some spark plug wires sparked, but not all. That usually points to bad spark plug wires or a bad distributor cap.
We need to dig a little deeper, go to: TEST 3: Checking The Distributor Cap For Spark.
CASE 3: None of the spark plug wires sparked. This confirms the engine isn't starting due to a lack of spark.
Next up, we need check if the ignition coil itself is generating spark. Head over to: TEST 2: Checking The Ignition Coil For Spark.
TEST 2: Checking The Ignition Coil For Spark
The ignition coil (which is located in the distributor) is tasked with generating spark and sending it to the distributor cap.
From there, the distributor cap transfers it to the distributor rotor, which then delivers it to the metal terminals inside the cap.
Next, the spark moves through the distributor cap towers, into the spark plug wires, and finally to all four spark plugs.
In this test section, we're gonna take off the distributor cap and use a spark tester to check if the ignition coil is producing spark.
- If the ignition coil sparks: The problem is likely a faulty distributor cap or rotor, stopping the engine from starting.
- If there's no spark: We'll move on to TEST 4 and keep troubleshooting.
IMPORTANT: As you check the ignition coil for spark, the distributor rotor should rotate as the engine cranks. If the distributor rotor does not rotate, you've got a busted timing belt causing the engine no-start problem.
Let's begin:
- 1
Take off the distributor cap from the distributor.
NOTE: Make sure the distributor stays connected to all its electrical connectors. - 2
Attach the spark tester to the ignition coil's metal terminal.
NOTE: The spark tester might slip off while cranking the engine. Wrapping them together with black electrical tape can help keep them secure and ensure solid metal-to-metal contact. - 3
Use a jump-start cable to Ground the spark tester by connecting it to the battery's negative (-) terminal.
- 4
Have your helper crank the engine while you keep an eye on the spark tester.
- 5
You'll see one of two results:
1.) The spark tester sparks.
2.) The spark tester DOES NOT spark.
Alright, let's break down what your test results tell you:
CASE 1: The spark tester sparked. This is the correct test result.
If you've already:
- Confirmed that none of the four spark plugs sparked (TEST 1).
- Verified in this test that the ignition coil is sparking.
Then the reason there's no spark at the spark plug wires is a bad distributor cap or rotor. They need replacing.
And if the spark plug wires are just as old as the distributor cap and rotor, it's a good idea to replace them too.
CASE 2: The spark tester DID NOT spark. No spark usually points to one of these issues:
- The ignition coil is faulty.
- The ignition coil isn't getting power.
- The igniter isn't sending the ignition coil its activation signal.
Next up, let's see if the ignition coil is getting power. Head over to: TEST 4: Making Sure The Ignition Coil Is Getting Power.