Identifying the Distributor Coil
The distributor coil, also known as the ignition coil, is a crucial component in the ignition system of older vehicles with internal combustion engines. It is responsible for converting the low voltage from the battery into a high voltage that is necessary to ignite the spark plugs, initiating the combustion process. Identifying the distributor coil is essential for diagnosing and resolving ignition problems.
Visual Examination:
The distributor coil is typically located on top of the distributor, an assembly that houses the ignition points or electronic ignition module. It has two terminals, one that connects to the battery and another that distributes high voltage to the spark plugs. The coil is usually encased in a black or gray plastic housing and has the primary and secondary windings.
Other Identifying Features:
Apart from visual examination, here are some additional characteristics that can help identify the distributor coil:
Coil Markings: The coil may have markings indicating its manufacturer, part number, and specifications. These markings can be found either on the side of the coil or on a label attached to it.
Resistance Measurements: Using a multimeter, you can measure the resistance of the primary and secondary windings of the coil. The primary winding typically has a resistance of a few ohms, while the secondary winding has a resistance in the thousands of ohms.
Voltage Test: With the ignition key turned to the “On” position, you can use a voltmeter to measure the voltage at the positive terminal of the coil. It should show battery voltage, indicating that the coil is receiving power.
Locating the Coil
The distributor coil is typically located on the side of the distributor. It is a small, round object with two terminals. One terminal is connected to the positive terminal of the battery, and the other terminal is connected to the points. The coil is responsible for generating the spark that ignites the air/fuel mixture in the cylinders.
Identifying the Distributor Coil
There are a few ways to identify the distributor coil. One way is to look for the two terminals. Another way is to look for the coil wire. The coil wire is a thin, insulated wire that connects the coil to the distributor cap. Finally, you can also look for the coil’s resistance. The coil’s resistance should be between 0.5 and 1.5 ohms.
If you are having trouble locating the distributor coil, you can consult your vehicle’s service manual. The service manual will contain a diagram of the distributor, which will show you the location of the coil.
Checking the Distributor Coil
Once you have located the distributor coil, you can check it to see if it is working properly. There are a few different ways to check the coil. One way is to use a multimeter to measure the coil’s resistance. Another way is to use a spark tester to check for spark. Finally, you can also check the coil by replacing it with a known-good coil.
If you are not comfortable checking the distributor coil yourself, you can take your vehicle to a mechanic to have it checked.
Checking for Corrosion or Damage
The distributor coil is a component in the distributor that helps generate electrical sparks to ignite the fuel-air mixture in the engine’s cylinders. Over time, the coil may become corroded or damaged, which can affect the vehicle’s performance and efficiency.
### Visual Inspection
Begin by visually inspecting the distributor coil for signs of damage or corrosion. Look for any cracks, breaks, or burn marks on the coil casing. Also, check the electrical terminals and wiring for any loose connections or damaged insulation.
### Continuity Test with Multimeter
Use a multimeter to test the continuity of the distributor coil. Set the multimeter to the ohms scale and connect the probes to the terminals of the coil. A good coil will have a low resistance reading, typically below 5 ohms. If the reading is high or infinite, the coil may be damaged and needs to be replaced.
### Resistance Test with Ohmmeter
An ohmmeter can be used to measure the resistance of the distributor coil’s primary and secondary windings. The primary winding should have a resistance of around 0.5 to 2 ohms, while the secondary winding should have a resistance of 5 to 15 kohms. Deviations from these values may indicate a problem with the coil.
Testing Resistance
To test the resistance of the distributor coil, you will need a multimeter set to the ohms range. Disconnect the distributor coil from the vehicle’s electrical system. Connect the multimeter leads to the terminals of the coil. The resistance reading should be within the manufacturer’s specifications. If the resistance reading is too high or too low, the coil is faulty and should be replaced.
Checking Coil Resistance
| Coil Type | Primary Resistance | Secondary Resistance |
|---|---|---|
| Internal coil | 0.4-2.0 ohms | 6,000-15,000 ohms |
| External coil | 0.5-1.5 ohms | 6,000-15,000 ohms |
When testing the resistance of the distributor coil, it is important to use a multimeter that is in good working order. A faulty multimeter can give inaccurate readings, which could lead to misdiagnosis of the coil. If you are not sure how to use a multimeter, it is best to consult with a qualified mechanic.
If the distributor coil is found to be faulty, it should be replaced as soon as possible. A faulty coil can cause a variety of problems, including engine misfires, stalling, and poor fuel economy.
Inspecting Spark Plug Wire Connections
The spark plug wires carry high-voltage electricity from the distributor coil to the spark plugs. Faulty wire connections can cause the engine to misfire or run poorly.
- Locate the spark plug wires. They are usually black or red and are connected to the distributor cap and the spark plugs.
- Inspect the wires for any damage, such as cracks, cuts, or breaks. Also, check for any loose or corroded connections.
- Remove the spark plug wire from the distributor cap and the spark plug. If the connection is difficult to remove, do not use pliers because you could damage the wire.
- Inspect the inside of the boot (the rubber covering) that connects the spark plug wire to the distributor cap and the spark plug. Look for any corrosion, carbon buildup, or moisture.
- Reinstall the spark plug wire by pushing it onto the distributor cap and spark plug. Make sure the connection is snug and secure.
Spark Plug Wire Resistance Test
You can use a multimeter to test the resistance of the spark plug wires. The resistance should be between 5,000 and 10,000 ohms per foot of wire. If the resistance is too high, the wire may be damaged and should be replaced. If the resistance is too low, the wire may be shorted to ground and should also be replaced.
| Resistance | Condition |
|---|---|
| 5,000-10,000 ohms/ft | Good |
| < 5,000 ohms/ft | Shorted to ground |
| > 10,000 ohms/ft | Damaged |
Using a Dwell Meter
A dwell meter is a specialized tool used to measure the dwell angle of a distributor coil. The dwell angle refers to the period during which the electrical current flows through the coil, allowing it to generate the spark required for ignition. Measuring the dwell angle can provide insights into the health of the distributor coil and ignition system.
Materials Required:
- Dwell meter
- Ignition coil wire
- Ground wire
Procedure:
- Disconnect the negative terminal of the battery to prevent electrical shock.
- Connect the positive lead of the dwell meter to the positive side of the coil.
- Attach the negative lead of the dwell meter to the negative terminal of the battery.
- Connect the ignition coil wire to the “Ignition” terminal of the dwell meter.
- Connect a ground wire from the engine to the ground terminal of the dwell meter.
- Start the engine and observe the dwell angle reading on the meter. The dwell angle should be within the specifications provided by the vehicle manufacturer. (Refer to the table below for typical dwell angle values.)
Typical Dwell Angle Values:
| Engine Type | Dwell Angle (Degrees) |
|---|---|
| 4-cylinder | 28-32 |
| 6-cylinder | 24-28 |
| 8-cylinder | 22-26 |
Utilizing an Ohmmeter
An ohmmeter is a valuable tool for testing the distributor coil’s resistance. Here’s how to proceed:
1. Disconnect the Coil:
Unplug the coil’s electrical connections to isolate it for testing.
2. Set the Ohmmeter:
Ensure the ohmmeter is set to the appropriate resistance range (typically 0-1000 ohms). The exact range may vary depending on the multimeter you are using.
3. Identify Coil Terminals:
Locate the two terminals on the coil, usually marked as “positive” and “negative.” Connect the ohmmeter’s leads to these terminals.
4. Observe Reading:
Take note of the resistance value displayed on the ohmmeter. A typical range for distributor coils is between 0.5 and 5 ohms.
5. Check Normal Function:
If the measurement falls within the acceptable range, it indicates that the coil is functioning normally.
6. Check for Open Circuit:
An infinite resistance reading or “OL” on the ohmmeter indicates an open circuit in the coil. This means the coil is faulty and needs to be replaced.
7. Check for Short Circuit:
A very low resistance reading, close to 0 ohms, suggests a short circuit in the coil. This condition can also cause coil failure and requires replacement.
| Resistance Reading | Indication |
|---|---|
| 0.5 – 5 ohms | Normal operation |
| OL (infinite resistance) | Open circuit; replace coil |
| Close to 0 ohms | Short circuit; replace coil |
Replacing the Coil
If you have confirmed that the coil is faulty and needs to be replaced, follow these steps:
1. Gather the necessary tools and materials
- New distributor coil
- Screwdriver
- Wrench
2. Disconnect the battery
This will prevent any electrical shocks while working on the distributor.
3. Remove the distributor cap
Locate the distributor cap and gently pry it off.
4. Locate the coil
The coil is usually located inside the distributor cap.
5. Disconnect the wires
Gently disconnect the wires connected to the coil.
6. Remove the bolts
Use a wrench to remove the bolts holding the coil in place.
7. Remove the old coil
Carefully lift out the old coil.
8. Install the new coil
Reverse the steps above to install the new coil. Be sure to tighten the bolts securely.
9. Reconnect the wires
Reconnect the wires to the coil.
10. Replace the distributor cap
Carefully replace the distributor cap and secure it.
11. Reconnect the battery
Tighten the battery terminals to reconnect the battery.
12. Start the engine
Start the engine and check if the problem is resolved.
Troubleshooting Common Issues
9. Replace the Coil
If the coil is damaged beyond repair, replacement is the only option. Follow these steps to replace the coil:
- Disconnect the negative battery terminal.
- Remove the distributor cap and rotor.
- Unbolt the distributor body from the engine.
- Disconnect the electrical connector from the coil.
- Remove the old coil from the distributor.
- Install the new coil into the distributor.
- Reconnect the electrical connector to the coil.
- Bolt the distributor body back to the engine.
- Install the distributor cap and rotor.
- Reconnect the negative battery terminal.
Start the engine and check for proper operation. If the engine starts and runs smoothly, the coil replacement was successful.
Here’s a table summarizing the possible causes and solutions for common distributor coil issues:
| Problem | Cause | Solution |
|---|---|---|
| Engine won’t start | Open circuit in coil | Replace coil |
| Engine runs rough | Weak spark from coil | Clean or replace coil |
| Engine stalls at high RPMs | Coil overheating | Check and correct ignition timing |
Safety Precautions
Before attempting to check the distributor coil, it is crucial to adhere to safety precautions:
1. Disconnect the Battery
Prior to any work on the electrical system, the battery’s negative terminal should be disconnected. This will prevent any electrical shocks or accidental ignition.
2. Wear Appropriate Safety Gear
Protect your eyes by wearing safety glasses and your hands by wearing gloves. The distributor cap can be sharp and may contain electrical hazards.
3. Allow for Coolant Time
If the engine has recently been running, allow sufficient time for the coolant to cool down before working near the distributor. Steam or hot coolant may cause burns.
4. Use Insulated Tools
Employ insulated tools when handling electrical components. This will minimize the risk of electric shocks or short circuits.
5. Keep the Work Area Clean
Maintain a clean work area free of loose wires or debris. This will prevent accidental connections and potential hazards.
6. Avoid Naked Flames
Do not expose the work area to naked flames or sparks. Gasoline and other fluids used in vehicles are highly flammable.
7. Ground Yourself
Before handling any electrical components, discharge static electricity by touching a grounded surface. This will prevent damage to sensitive electronics.
8. Respect Sharp Edges
The distributor cap and other components may have sharp edges. Handle them with care to avoid cuts or punctures.
9. Avoid Contact with Battery Acid
In case of battery acid contact, immediately flush the affected area with plenty of water and seek medical attention if necessary.
10. Be Aware of Your Surroundings
Stay alert and be aware of potential hazards in your surroundings. Ensure the work area is well-ventilated and free of obstructions.
| Safety Precaution | Description |
|---|---|
| Disconnect the Battery | Disconnect the battery’s negative terminal before working on the electrical system. |
| Wear Safety Gear | Wear safety glasses and gloves to protect your eyes and hands. |
| Allow for Coolant Time | Allow the engine to cool down before working near the distributor. |
| Use Insulated Tools | Use insulated tools when handling electrical components. |
| Keep the Work Area Clean | Maintain a clean work area free of loose wires or debris. |
| Avoid Naked Flames | Avoid exposing the work area to naked flames or sparks. |
| Ground Yourself | Discharge static electricity by touching a grounded surface before handling electrical components. |
| Respect Sharp Edges | Handle the distributor cap and other components with care to avoid cuts or punctures. |
| Avoid Contact with Battery Acid | Flush the affected area with water and seek medical attention in case of battery acid contact. |
| Be Aware of Your Surroundings | Stay alert and be aware of potential hazards in your surroundings. |
How to Check Distributor Coil
The distributor coil is an important part of the ignition system in an internal combustion engine. It is responsible for converting the low voltage from the battery into the high voltage that is needed to create a spark at the spark plugs. A faulty distributor coil can cause a variety of engine problems, including misfiring, rough idling, and stalling.
There are a few different ways to check a distributor coil. One way is to use a multimeter to measure the resistance of the coil. The resistance should be between 0.5 and 1.5 ohms. Another way to check the coil is to use a spark tester. A spark tester is a tool that can be used to check the strength of the spark at the spark plugs. If the spark is weak or nonexistent, it could be a sign that the distributor coil is faulty.
If you suspect that your distributor coil is faulty, it is important to have it checked by a qualified mechanic. A faulty distributor coil can cause serious engine problems, so it is important to have it replaced as soon as possible.
People Also Ask
How do I know if my distributor coil is bad?
There are a few signs that may indicate a faulty distributor coil, including misfiring, rough idling, and stalling. You can also use a multimeter or a spark tester to check the coil for proper resistance and spark strength.
Can I replace a distributor coil myself?
Replacing a distributor coil is not a difficult task, but it is important to follow the manufacturer’s instructions carefully. If you are not comfortable working on your vehicle, it is best to have the coil replaced by a qualified mechanic.
How much does it cost to replace a distributor coil?
The cost of replacing a distributor coil will vary depending on the make and model of your vehicle. However, you can expect to pay between $50 and $200 for the coil itself, plus labor costs.
