5 Causes Why a Starter is Not Engaging

Car Starter Motor

Picture this… You have an early morning presentation with seed investors. It is a meeting that is going to change your life.

You pop into your garage in a hurry, but the car will not start when you turn on the ignition key.

You can hear the starter spinning, but it’s not engaging with the flywheel. What could be wrong?

5 Causes of Starter Not Engaging

  1. Low Battery Voltage
  2. Faulty starter motor solenoid
  3. Starter motor Plunger or Pinion
  4. Faulty Wiring to starter
  5. Flywheel damages

There could be a lot of different reasons causing your starter to not engage properly, but mainly there is an internal issue with the starter motor. Here is a more detailed list of the 5 most common causes why your starter won’t engage.

1. Low battery voltage

Bad Car Battery

When you are experiencing battery problems, the first culprit is your battery voltage, so you should check this first. The battery powers the starter, and if it is not working, the starter will fail to engage completely.

Charge your car battery fully, and you can even try to replace the car battery if you have another one you know works. You can also try jump-starting your car from the car battery of another car if you have the knowledge.

Next, check out whether your battery terminals are corroded. For this, you will notice a whitish or greenish substance on the terminals.

If you notice any corrosion on the battery terminals, you should remove the battery cable clamps and remove the terminals carefully.

RELATED: Does Auto-Start/Stop Wear Out Engine Components?

2. Starter solenoid

Starter Solenoid

The starter solenoid is located on top of the starter. When you turn the key, it is the starter solenoid that pushes a plunger inside the starter motor, pushing the pinion towards the flywheel.

Use a jumper wire to ground the solenoid to a bolt. Start the ignition and listen for sounds coming from the solenoid. If the click is loud and solid, then the solenoid is working fine but if you hear a weak click, then recheck the wiring between the solenoid and starter. Electrical wires can, with time, become dirty, loose, and broken.

3. Starter motor Plunger or Pinion

Starter Motor Diagram

If your starter solenoid seems to be fine, there might be another problem inside your starter motor. The parts that can accomplish this is the starter plunger or the starter pinion.

It is time to dismantle the starter and check inside for the pinion gears. These are often placed at the front of the starter. The pinion gears engage the flywheel in firing up your engine.

With time, these gears get worn out and cause problems with the starter engaging. It is time to purchase a new piston gear if it moves in both directions when you try to rotate it.

4. Faulty Wiring to starter

Corrosion On Cable

There may also be a situation when the starter gets electrics to make a sound, but not enough to actually turn the starter. This can happen if there is a bad starter cable between the car battery and the starter or corrosion at any connection.

Clean all connections both at the starter and the battery to ensure there is no bad connection. You can often locate bad connections by feeling on the cable connection; it will create a lot of heat if there is a bad connection.

5. Flywheel damages

Car Flywheel

You can identify the flywheel as the large wheel that is located between the engine and transmission. The starter pinion gears engage it to start the engine. What you should be looking for in a faulty flywheel are worn or damaged gears.

While the car is on neutral, rotate the crankshaft using a ratchet. As you move it, watch the behavior of the flywheel. You will need to replace it if you notice that the gears are damaged.

It would rarely happen suddenly; it is more common to have a wrong flywheel installed on the car.

Written by: Magnus Sellén

Founder, owner & main author of Mechanic Base. I have been repairing cars for more than 10 years, specialized in advanced diagnostics & troubleshooting. I have also been a drifting driver and mechanic for over 7 years.