Car Won't Start After Replacing Ignition Coil, Car Won’t Start After Replacing Ignition Coil [5 Effective Solution], KevweAuto

Car Won’t Start After Replacing Ignition Coil [5 Effective Solution]

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Having your car fail to start after replacing the ignition coil is frustrating. You fixed the bad part, so why doesn’t the engine turn over? Don’t panic yet, There are a few common missteps that can lead to no-start conditions even with a new coil.

This article explores the top reasons an engine won’t crank after a coil replacement along with tips to correctly diagnose and resolve the no-start issue. With a few simple checks and repairs, you can get your car firing on all cylinders again.

Key Reasons the Car Won’t Start After a Coil Replacement

Car Won't Start After Replacing Ignition Coil, Car Won’t Start After Replacing Ignition Coil [5 Effective Solution], KevweAuto

Here are the most common causes of a continued no-start problem after installing a new ignition coil:

1. Incorrect Coil Installation

Improperly seated coil towers or reversed coil wiring can prevent spark generation and fail to start the car. Taking care to correctly install the replacement coil is key.

2. Additional Bad Coils

If other worn coils were not identified and left in place, the new coil alone may not be sufficient to allow starting. All faulty coils must be replaced.

3. Crankshaft Sensor Failure

A bad crank sensor provides inaccurate timing signals to the ignition system. This can prevent spark even with a new coil.

4. Low Battery Voltage

Weak battery output can leave insufficient voltage to generate a strong spark for ignition, even if the coil is fine.

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5. Immobilizer System Glitch

Anti-theft issues like a failed transponder key or ECU security malfunction can also lead to no-start conditions after a coil swap.

Methodical Diagnosis to Isolate the No-Start Cause

To identify the real reason your car fails to start after the coil replacement, methodically test:

1. Verify Proper Coil Installation

Check that coil electrical connectors are fully latched and tower mounting bolts are tight. Swap with another coil if orientation seems reversed or positioning is off.

2. Scan for Engine Codes

Retrieve any diagnostic trouble codes (DTCs) for clues on failures like additional bad coils, crank sensor issues, or security problems. Research codes to understand where to focus efforts next.

3. Inspect Fuses

Make sure the coil fuse in the underhood box is not blown from an improper installation. Also check ECU and fuel pump fuse integrity to ensure they have voltage.

4. Test Battery Voltage

Use a multimeter to verify battery voltage is 12+ volts when the key is on. Check voltage drops when cranking to see if it’s discharging heavily.

5. Try an Alternate Coil

Swap the new coil with a known-good used coil from another cylinder. See if the no-start condition changes or engine tries to fire.

By following a diagnostic routine, you can isolate the specific reason the new coil is not resolving the starting issues and make further repairs.

Correcting an Improper Coil Installation

If you find the new coil was not properly installed:

  • Remove the coil and inspect the oven seal for dirt, tears or blockage from old grease. Clean or replace if needed.
  • Check coil mounting holes for issues like cross-threading or debris obstruction. Allow good mating contact.
  • Ensure locking bolts are tightened to factory torque specs to avoid arcing risks. Do not over-tighten.
  • Confirm electrical harness plug is clicked fully into coil receptacle for continuity. Use dielectric grease.
  • Refer to a shop manual for your specific vehicle’s coil orientations and locations if unsure.
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Taking care to correctly mount the replacement coil allows it to work as designed so the engine can start.

Identifying and Replacing Additional Faulty Coils

Car Won't Start After Replacing Ignition Coil, Car Won’t Start After Replacing Ignition Coil [5 Effective Solution], KevweAuto

If you determine other coils are also bad:

  • Perform resistance testing on remaining coils to identify any out of spec readings signaling failure.
  • Visually inspect coils for damaged towers, cracked casing, or burned electrodes.
  • Move the new coil to the cylinder with the worst misfire and replace other faulty coils one at a time with manufacturer recommended parts.
  • Clear codes and verify engine starts and runs smoothly before declaring coils fixed.
  • Consider replacing the entire set if coils are old or service history is unknown.

Finding and changing all bad coils restores strong ignition to all cylinders for reliable everyday starting.

Fixing a Defective Crankshaft Position Sensor

If the crank sensor tests defective:

  • Inspect sensor mounting and wiring for damage, corrosion, or loose connections.
  • Determine if sensor air gap spacing to flywheel is out of spec – reposition if needed.
  • Install a new OE sensor if resistance testing indicates internal failure or wiring repairs don’t resolve issues.
  • Clear codes and verify engine starts and runs properly before driving.

The crank sensor must provide accurate input to the ignition system telling it when to fire the coil packs. A new sensor paired with the new coil gets things in sync again.

Charging or Replacing a Weak Car Battery

Low battery voltage problems can be resolved by:

  • Cleaning corroded battery terminals or charging the battery to 12+ volts if it is unable to hold a charge.
  • Testing the alternator output with a multimeter to see if the charging system needs repairs.
  • Replacing the battery if it is more than 3-5 years old. Match oem specifications for best performance.
  • Verifying ground strap connections are free of dirt/debris to allow proper current flow.
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With ample battery power, the ignition system can fire the new coil and allow the engine to start up.

Professional Assistance with Ongoing No-Start Issues

Car Won't Start After Replacing Ignition Coil, Car Won’t Start After Replacing Ignition Coil [5 Effective Solution], KevweAuto

If you’ve made the above repairs and the car still won’t start, have a professional technician diagnose further:

  • They can test ECU and security system operation to spot any immobilizer faults prohibiting starting.
  • Dealership computer scans detect issues with anti-theft systems that aftermarket tools often cannot.
  • Diagnosing intermittent no-start problems may require specialist tools to simulate conditions.
  • Checking fuel pump current ramp-up and relay activation goes beyond typical DIY capabilities.

Seeking help from a professional mechanic is recommended if you’ve replaced the coil and battery but the car still won’t start reliably. Their expertise and equipment can get to the bottom of remaining issues.

Preventing Future No-Start Conditions

Here are some tips to help avoid a repeat no-start situation after future coil replacements:

  • Carefully follow factory service manual procedures for coil pack R&R rather than winging it.
  • Confirm any salvaged used coils have integrity through resistance testing before installing.
  • Routinely check engine codes for early detection of crank sensor or other faults.
  • Maintain the battery’s charge level and condition to avoid low voltage issues.
  • Use dielectric grease on electrical connections and avoid touching contacts to prevent shorts.

Staying meticulous during repairs and attentive to component condition keeps your ignition system in top shape for consistent starting capabilities.


While a faulty coil is the obvious suspect for engine no-start conditions, other issues like additional bad coils, sensor failures, electrical shorts, or immobilizer faults can still prevent starting even after a new coil is installed. Following structured diagnosis procedures and making necessary repairs will get your car firing on all cylinders once again. Seek professional assistance if needed when DIY efforts cannot resolve ongoing starting difficulties.

Ejenakevwe Samuel

I'm Ejenakevwe Samuel, and my blog is all about sharing the love for cars. Through my blog, I pour my heart into educating fellow car enthusiasts in everything they need to know about their beloved rides. Whether it's driving tips, maintenance tricks, or the latest trends, I aim to empower others to make informed decisions and take care of their vehicles like a pro.

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