Classic car refers to cars that are more than 25 years old and have a vintage and antique appearance. Many people prefer to own classic cars to gain attention and admiration from their friends. In addition, these are famous because of the historical point of view. However, many people face issues with their ignition coil, which can lead to stalling, backfiring, engine overheating, and compromised fuel economy.
Classic car coil getting hot can be due to a faulty ignition module, poor and weak grounds, water and engine oil contamination, worn-out spark plugs, key in the ignition, degraded insulation material, use of incorrect coil, faulty ballast resistors, old batteries, and heavy engine loads.
I wanted to start my classic car yesterday morning, but the engine could not start. I tried to start the engine several times but saw a check engine light on the screen. I faced difficulty starting my vehicle because of a faulty ignition coil, which was not providing sufficient voltage for the air and fuel mixture to burn. I replaced the ignition coil with a new one because of the damaged insulation layer.
| Causes | Solutions |
| Faulty ignition module | Use voltage regulators |
| Poor and weak grounds | Check ground connections |
| Water and engine oil contamination | Check seals, gaskets, and valves |
| Worn-out spark plugs | Replace spark plugs |
| Key in ignition | Remove the key from the ignition |
| Degraded insulation material | Inspect chemical, oil, and coolant leakage |
| Use of incorrect coil | Use coils that are compatible with the electric system |
| Faulty ballast | Replace ballast resistors |
| Old batteries | Change dead batteries |
| Heavy load on the engine | Avoid overloading your classic cars |
Faulty ignition module
The ignition control module is the part of the ignition coil to control its functioning. It helps monitor the ignition timing and allows the spark plug to generate air and fuel mixture.
The ignition control module is the brain of the ignition system. The overheating coil issue comes from a faulty ignition control module that cannot control its functioning.
The coil works continuously to ignite the air and fuel mixture. The control module is vulnerable to failure because of overheating, age-related wear and tear, and voltage fluctuations.
Moreover, the control module also becomes bad because of faulty electric connections, excessive vibrations from broken engine mounts, and harsh driving conditions.
I always prefer to install surge protectors in my classic car to protect the electric components from fluctuating voltage and electric problems. Voltage regulators are beneficial because they regulate the electric current supply to the respective electric components.
Poor and weak grounds
Classic cars contain several ground connections to provide an additional path for the current flow during short circuits and voltage spikes.
Coil overheating issues in classic cars come from poor and weak ground connections. It increases the resistance of electric current in the circuit, leading to higher current flow to different electric components.
Ignition coils are designed to hold the maximum electric current for their functioning. Higher voltage increases their component’s temperature and also leads to engine issues.
Ground connections become poor because of corrosion, frayed wiring, and loose attachments. It is necessary to check the ground connections in your cars to ensure the correct current flow to the various systems.
Water and engine oil contamination
Ignition coils are also vulnerable to water and oil contamination because of their damaged insulation layer. These cannot sufficiently generate the electric current for air and fuel ignition.
Water and oil contamination affect their normal functioning, and they work harder to ignite the ignition mixture, which leads to overheating.
Water contamination problem comes from condensation in the engine compartment, head gasket failure, which allows coolant to seep into several areas, and incorrectly sealed parts.
In addition, you can face oil contamination issues because of overfilled engine oil, high oil pressure, worn-out piston rings, and damaged cylinder walls.
My friend also faced the same issue, and he complained about the burning smell from the engine and difficulty starting his car. I told him the problem came because of the failure of the ignition coil, which was not providing sufficient electric current to the spark plug.
I suggested him to inspect the engine parts and replace the worn-out gaskets, seals, and cylinder walls with new ones. He opened the hood and saw the broken piston ring seal, interrupting the coil functioning and leading to overheating.
Worn-out spark plugs
Ignition coils supply the electric current to the spark plugs that generate a spark to ignite the ignition mixture. Sometimes, these spark plugs become faulty, which leads to an increased gap.
The coil sends more power to fill the gap between the spark plugs so they can provide the spark for ignition. Chances of ignition coil failure and overheating increase because of working at higher output.
Spark plugs are vulnerable to damage because of carbon soot accumulation, dirty air filters, continuous driving at slow speed, oil contamination, heat damage, and dirty fuel injectors.
It is better to replace the spark plugs when you face difficulty in starting your car engine. I also faced the issue because of the failure of the spark plug, so I turned off the engine for cooling and spark plug replacement.
I disconnected the battery and removed the spark plug wires from the connectors. I installed the new spark plug and attached its wirings to the connectors.
Key in ignition
Classic car coil is more susceptible to overheating if you do not remove the key from the ignition switch. The key in the ignition switch allows it to continuously supply the power from the batteries to the spark plugs.
Many people do not turn off the ignition in their class cars when they have to wait on the roads for a few minutes. My friend also used to do this because he thinks frequently starting the engine increases the risk of wear and tear of their components.
I told him that it increases the coil’s temperature and the risk of failure. It is better to turn off the ignition and remove the key from the switch while waiting on the traffic signals and busy lanes of roads.
Degraded insulation material
Classic car ignition coils contain epoxy resins in their windings that protect against electric currents and heat conduction.
The degradation of insulated material is common because of damaged primary windings.
Oil leakages from the broken gaskets and damaged seals cause degradation of insulated material. In addition, excessively high temperatures can also damage the insulation coating.
Inspect the engine parts regularly to ensure no chemicals, oil, or coolant leakages.
Use of incorrect coil
Many people face issues while starting their car because of using the incorrect coil. You have to use it according to the voltage of the electric system in your classic cars.
The overheating problem comes from the use of incompatible ignition coils in vehicles that are incompatible with the electric system.
High voltage current increases their temperature and leads to engine stalling and backfiring because of unburnt fuel. It is necessary to select the right coil that is compatible with the electric system. You should not add a 6V coil with a 12V system because of the high current flow.
Faulty ballast
Ballast resistors are the electric devices of switches that control the voltage supply to the coils. Sometimes, these resistors fail to perform their function, leading to a high current supply.
High voltage supply causes overheating issues and complete failure of this component. Ballast is vulnerable to failure because of high temperatures, aging, faulty batteries, and electric issues.
You cannot repair the faulty ballast, and you have to replace it to fix the electric issues.
Old batteries
You can face coil overheating issues in your classic car because of old and dead batteries. These batteries cause an insufficient voltage supply to this part.
They work harder to supply sufficient electric current to the spark plug for ignition. Batteries in vehicles can last for 5 to 7 years with proper maintenance.
You have to replace the dead and old batteries with new ones if you face issues with the electric components of your cars.
Heavy load on the engine
Classic car coil can also overheat because of the high temperature of the engines. The temperature inside engine compartments rises because of heavy loads.
The issue comes because of the overloading of vehicles. Engine components work harder and require more power to pull the heavy loads.
You should not overload your car and add weight according to its maximum weight-carrying capacity because it can cause damage to engine parts.
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