How do you check a coil on a car?

Asked By: Geronima Jorcano | Last Updated: 1st April, 2020
Category: automotive auto parts
4.3/5 (150 Views . 25 Votes)
To test the ignition coil connect the ohmmeter's two test leads to the coils primary terminals (+ and -). Most coils should read between 0.4 and 2 ohms. Zero resistance would indicate a shorted coil while a high resistance reading would indicate an open coil.

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Likewise, people ask, how can you tell if an ignition coil is bad?

Here are some of the most common symptoms of bad ignition coil.

  1. #1 – Backfiring.
  2. #2 – Poor Fuel Economy.
  3. #3 – Engine Misfiring.
  4. #4 – Vehicle Stalling.
  5. #5 – Engine Jerking, Rough idling, Poor Power.
  6. #6 – Check Engine Light On / DTC Code.
  7. #7 – Engine Hard Starting.
  8. CNP Coil Type.

Additionally, how do you test a 12v ignition coil? You can test a 12-volt ignition coil for effectiveness by checking the resistance of its wire windings with a multimeter.

  1. Disconnect your engine's main negative battery cable with a wrench.
  2. Pull the main ignition coil wire, the one that leads to the distributor, off the coil.

Regarding this, how do you check a coil with a multimeter?

Test the coil with a multimeter. Disconnect the coil pack's electrical connector then remove the coil pack from your car's engine using a wrench. Set the ohmmeter/multimeter to 200 ohms range then turn it on. Using a meter lead, attach the spark plug wire terminal to each coil.

Can you drive with bad ignition coils?

The answer is you should not. You can drive the car until it breaks down completely (and it will). Once a fuel part starts leaking while a car is running, a fuel drip can be the formula for fire if you get sparks from a spark plug wire or an ignition coil that is faulty. Something like this could be the end result.

29 Related Question Answers Found

What does a bad ignition coil sound like?

If you try to start your engine up and you hear a spluttering sound repeatedly, then you are likely experiencing an engine misfire that can be attributed to a bad ignition coil. You may still be able to drive your vehicle, but you will hear a lot of strange noises and even feel jerkiness as you accelerate the vehicle.

Can I replace just one ignition coil?

You can replace one coil at a time or all at the same time. I would however recommend having all spark plugs replaced with the coils so you do not have to remove coils twice.

Will a new ignition coil improve performance?

A high performance ignition coil helps engine performance four important ways. First, the higher voltage allows for a larger spark plug gap, which results in a more robust initial flame kernal at the start of combustion. The result is a real-world engine torque increase.

How much does it cost to replace ignition coils?

The average cost for an ignition coil replacement is between $223 and $328. Labor costs are estimated between $58 and $75 while parts are priced between $165 and $253. Estimate does not include taxes and fees.

Should you replace ignition coils with spark plugs?


The most common component to replace in conjunction with the ignition coils are the spark plugs. Worn spark plugs can cause unnecessary load on the coils and there is often some overlap in the labor required to replace both components.

Where is ignition coil A located?

The Ignition Coils are located on the cylinder head above their respective cylinders (shown, Cylinder One). The Ignition Coils (with power output stages) are located on the right side of the engine on the valve cover (shown, Cylinder One).

What happens if ignition coil gets wet?

When the coil gets wet, or there is moisture near it, there is enough of a path for some (or all) of the spark energy to get out right through the insulation. The voltage in a coil can get somewhere the neighborhood of 30k volts, this requires a good bit of quality insulation to contain.

Will a bad coil pack throw a code?

A shorted or open fuel injector solenoid, or a shorted or open coil will usually set a code, but a dirty or weak fuel injector or a weak coil probably won't set a code. Bad spark plug wires are a common cause of misfire codes.

How much voltage should be at the coil?


The coil becomes a transformer, stepping the voltage up. If your car uses a 12 volt battery, the 12 volts you put into the primary side of the coil will exit the secondary side as 30,000 volts!

How often should you replace coil packs?

But in general, my advice is, if you have more than about 75k miles on the car and a coil pack goes bad, replace them all. Back in the days , say 50 years ago, most cars would work wit one ignition coil to power all cylinders on 2 .

What would cause a coil not to fire?

The most common cause for a misfire is a problem related to the ignition system. Misfiring can be caused by loss of spark; imbalanced air/fuel mixture; or loss of compression. This includes worn, fouled or damaged spark plugs, bad plug wires or a cracked distributor cap.

What would cause an ignition coil not to fire?

A bad Crankshaft Position sensor is a common cause of no starts. The signal from this sensor goes to the PCM or ignition module that switches the ignition coil(s) on and off. In ignition systems with a single coil and distributor, a bad coil or a cracked distributor cap or rotor can prevent the spark plugs from firing.

How do I know if my coil is 6v or 12v?

You need to connect an amp meter in series with the coil and 6 volt battery. A 6 volt coil will draw 4 amps. If you have an accurate ohm meter, reading across the posts of a 12 volt coil should be about 3 ohms. A 6 volt coil is about half of that.

How do you troubleshoot an ignition coil?


How to Test Ignition Coils
  1. Safety First. Let your vehicle cool down, and put on the emergency brake.
  2. Remove the Ignition Coils. Find the ignition coils.
  3. Test the Primary Winding. Each ignition coil consists of two separate coils wrapped around each other: the primary winding and the secondary winding.
  4. Test the Secondary Winding.
  5. Solve the Problem.

Do you need a resistor with a 12 volt coil?

If a 6 volt ignition system is converted to 12 volts and a Delco style 12 volt coil with an internal resistor is installed as part of the conversion, no external resistors are required. The 12 volt battery must be connected so the negative (-) battery terminal is connected to ground.

Should there be power on both sides of a coil?

Yes, if the points are open and/or the electronic module is NOT CLOSED then you will measure battery voltage on both the coil (+) and coil(-) terminals. Since there is no current flowing through the coil (no path to earth) then both sides of the coil will be at the same potential.