The ignition coil, a vital component of any vehicle's starting system, is responsible for providing electricity to the spark plugs. When a car does not start, starts hard or stalls frequently, this element may have problems and needs to be replaced. Luckily, you can do some simple tests to see if the ignition coil is working properly or if you need to go to a mechanic or auto parts store. Read on to learn more.
Steps
Method 1 of 2: Perform the Spark Test
Step 1. Turn off the car and open the hood
As with most maintenance procedures, the car must be shut down and stationary. Open the hood and locate the ignition coil. Although the exact location varies from model to model, it is usually located near the fender, choke or under the distributor. Be aware that in vehicles that do not have a distributor, the spark plugs are connected directly to the coil.
- A safe technique for finding the ignition coil is to locate the distributor and follow the wire that connects it to the spark plugs.
- Before starting, it is best to wear safety glasses or other eye protection; Also get some insulated tools (especially pliers) to avoid electric shocks.
Step 2. Detach a spark plug lead from its housing and then from the spark plug to which it is attached
Usually these cables run from the distributor to each spark plug individually. To avoid any injury, be very careful when working on a car's electrical system and always use insulated gloves and tools.
- If the engine has been running for a while, be aware that the compartment under the hood will be quite hot and the components may be hot. It would be better to wait 5-10 minutes after turning off the vehicle before starting these operations.
- To save time and avoid possible spark plug damage, consider using a spark plug tester instead. Instead of connecting the actual spark plug to the lead, connect the test spark plug. Ground the alligator clip. Then ask your friend to start the engine, checking for sparks.
- Using a test spark plug also means avoiding exposing the combustion chamber to possible debris.
Step 3. Remove the spark plug using the correct socket wrench
To perform this task, the simplest thing is to use the specific socket wrench.
- From this point forward, be very careful not to drop any objects into the hole left free by the candle. Leaving some debris in its housing causes engine damage, and since retrieving something inside this hole is really difficult, it's better to be safe than sorry!
- Cover the cavity with a clean rag to prevent debris from entering the combustion chamber.
Step 4. Connect the spark plug back to its lead very carefully
You should find yourself with the cable connected to the distributor (at one end), while at the other end you will find the connector to the spark plug, but it is not inserted in its housing. Handle the spark plug with insulated pliers to avoid electric shock.
Step 5. Touch any metal part of the car with the threaded part of the spark plug
Then make sure that the spark plug (connected to its cable) touches a metal part of the engine with the threaded head. Any sturdy piece of metal inside the engine compartment will do, even the engine itself.
Again, remember to handle the spark plug with insulated pliers and, if possible, with gloves. Don't risk an electric shock just for neglecting protective clothing
Step 6. Remove the fuel pump fuse
Before starting to test the spark plug it is necessary to deactivate the pump. This will ensure that you cannot start the engine, thus allowing you to check for sparks in the coil.
- If there are no sparks, the combustion necessary to start the engine will not take place in the cylinder, but it will still be filled with fuel. Deactivating the pump fuse is to prevent this from happening, as it can seriously damage the motor.
- Check your manual to locate the location of the fuse in question.
Step 7. Ask a friend to start the engine
Have your assistant turn the ignition key: this will supply electricity to the car's system and, consequently, also to the spark plug in your hand (assuming the coil is working).
Step 8. Check for blue sparks
If the starter coil is working properly, you should see blue sparks at the tip of the spark plug when your assistant starts the engine. These are clearly visible sparks even in daylight. If you are unable to see them, then the coil is in trouble and should be replaced.
- Orange sparks are a bad sign. This means that the coil is not delivering enough energy to the spark plugs (there can be a variety of causes, such as a broken coil box, "weak" electrical power or worn connections).
- The last possibility is that there are no sparks. In this case the starter coil could be permanently dead, or one or more electrical connections are damaged or you have performed the test incorrectly.
Step 9. Put the spark plug back into its housing and restore the wiring carefully
Once the test has been completed, you must turn off the engine and carry out all the operations described above but in reverse order. Disconnect the spark plug from the cable, reinsert it in its seat and re-attach the cable to the connector.
Well done! You have performed a function test of the ignition coil
Method 2 of 2: Perform the Endurance Test
Step 1. Remove the coil from the vehicle
The test described above is not the only one you can put into practice to check the functionality of this element. If you have the ability to get a tool called an ohmmeter, which measures electrical resistance, then you can quantitatively assess the coil's ability to transmit energy, instead of proceeding with a qualitative examination like the one in the previous section. To proceed with this check you must remove the coil, so as to have access to its electrical terminals.
Refer to the vehicle maintenance manual for exact instructions on how to disassemble it. Most of the time it needs to be disconnected from the distributor cable and then unscrewed with a wrench. Always check that the machine is turned off before starting work
Step 2. Find the normal coil resistance values
Each vehicle has its own technical specifications regarding the electrical resistances of the system and therefore also of the coil. If the values you find are outside the expected range for your machine, then you know for sure that the item is damaged. You can usually find these specifications in the maintenance manual. However, if you can't find them, you can contact the dealer who sold you the vehicle or do some research online.
In general, most of the coils mounted on the transport means have a resistance between 0, 7 and 1.7 ohms for the primary winding, and between 7,500 and 10,500 ohms for the secondary winding
Step 3. Secure the ohmmeter connectors to the primary winding poles
The distributor has 3 electrical contacts: 2 on the sides and 1 in the middle. These can be internal or external, it makes no difference. Turn on the ohmmeter and touch one connector of each of the electrical contacts. Take note of the resistance values you read: this is the resistance of the primary winding.
Some modern coil models have a different contact configuration from the traditional one: always consult the vehicle maintenance manual to find out which ones correspond to the primary winding
Step 4. Put the connectors of the ohmmeter to the poles of the secondary winding
Attach a connector to the external contacts and touch the middle one, inside the coil (where the main wire connects to the distributor). Record the value you read on the instrument: this is the resistance of the secondary winding.
Step 5. Determine if the values you measured are within the normal range for the ignition coil
This is a very delicate part of the electrical system: if the primary and secondary resistance differ even slightly from the normal values, it will be necessary to replace the element, since it is clearly malfunctioning.
