Starting System Repair San Antonio

What are the symptoms of a bad starter motor: When starting a car with a fully charged battery, there is a single click or nothing happens at all. The starter motor doesn't run, even though there is a 12-Volt power at the starter control terminal.

Another symptom is when the starter motor runs, but fails to turn over the engine. Often, this might cause a loud screeching noise when starting the car. Of course, this could also be caused by damaged teeth on the ring gear of the flex plate or flywheel.

 

Starter solenoid

A typical starter solenoid has one small connector for the starter control wire (the white connector in the photo) and two large terminals: one for the positive battery cable and the other for the thick wire that powers the starter motor itself.

The starter solenoid works as a powerful electric relay. When activated, through the control terminal, the solenoid closes the electric circuit and sends the battery power to the starter motor. At the same time, the starter solenoid pushes the starter gear forward to mesh with the ring gear of the engine flex plate or flywheel.

Battery cables

As we mentioned, the starter motor requires very high electric current to turn over the engine. That's why it's connected to the battery with thick cables. The negative (ground) cable connects the negative "-" battery terminal to the engine cylinder block, or transmission, close to the starter.

The positive cable connects the positive "+" battery terminal to the starter solenoid. Often, a poor connection at one of the battery cables can cause the starter motor not to work.

How the starting system works:

1. When you turn the ignition key to ON position, the engine computer (PCM) checks if the ignition key security code matches (immobilizer). If yes, the engine is allowed to start.

2. When you turn the key to the START position, or press the START button, the engine computer (PCM) checks if the transmission is in Park or Neutral, if the brake pedal (Automatic) or clutch pedal (Manual) is depressed and if the steering lock is unlocked (in some cars).

3. If all checks pass, the engine computer activates the starter relay.

4. The starter relay closes the starter control circuit and activates the starter solenoid.

5. The starter solenoid closes the high-current circuit and sends power to the starter motor.

6. At the same time, the starter solenoid throws the starter gear forward to mesh it with the engine flex plate gear (or flywheel gear in a manual transmission). The flex plate (flywheel) is attached to the engine crankshaft.

7. The starter motor turns over the engine crankshaft fast enough to allow the engine to start. In cars with a push button start, the system disengages the starter motor as soon as the engine starts running.

Neutral safety switch

Automatic transmission range switch.

For safety reasons, the starter motor can only be operated when the automatic transmission is in Park or Neutral position. In a car with a manual transmission, the engine can only be started when the clutch pedal is depressed.

In cars with an automatic transmission, the transmission range switch works as a neutral safety switch. It sends the signal to the engine computer if the transmission is in Park or Neutral. In vehicles with a manual transmission, the clutch pedal switch performs the same role. It tells the engine computer if the pedal is depressed.

The job of the transmission range switch is to tell the vehicle computer (PCM) which gear the transmission is in. 

If your car has a gear indicator on the dash, you might be able to see when a transmission range indicator is not working.

The most common problem is when you shift the transmission into "Park" and the letter "P" doesn't show on the dash. This means that the vehicle computer (PCM) doesn't know that the transmission is in "Park" and will not allow the starter to operate.
 

Starting system problems

Starting system problems are common and not all of them are caused by a faulty starter motor. To find the cause of the problem, the starting system must be properly tested. If when you are trying to start the car, you hear that the starter cranks as usual, but the car doesn't start, then the problem is most likely not with the starting system. 

Most starter problems are caused by worn out or burned solenoid contacts, worn brushes and a commutator and worn armature bushings. The symptom of worn out solenoid contacts is when the solenoid clicks but the starter motor doesn't run. When the starter brushes are worn out, the starter motor doesn't make any noises. When front and rear armature bushings wear out, the armature rubs against the field shoes causing the starter motor to run slow and noisy. Many modern starter motors have small ball bearings instead of bushings.

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