The engine starting systems which are used in most vehicles have seen very little change over the last several decades. The system is actually quite simple and consists of just a few major components: The Starting Motor itself, the Starter Solenoid, the Ignition Switch, and usually a Safety Switch. These components are connected via associated electrical wiring. When you begin to start your vehicle, several events take place. Electrical current is routed from the battery through the ignition switch and any safety switches first before actually reaching the starting motor. These safety switches are in place to prevent you from accidentally starting the engine while the transmission is in gear. In a vehicle with an automatic transmission, the safety switch will not allow the engine to start unless the transmission is either in Park or Neutral. Likewise, a vehicle with a manual transmission will not start unless the clutch is disengaged or “pushed in”.
If all switches etc. are working correctly, then current is routed to the starter solenoid. This solenoid is what actually mechanically engages the starting motor to the engine in order to start the vehicle. After you release the key, the starter solenoid then disengages the starting motor whilst the engine is running. The starter solenoid is usually located upon the body of the starting motor itself, and in some cases is built into the starting motor as an integral part. Some vehicles (mainly of Ford manufacture) also use what is commonly called a “Starter Relay”.
If your vehicle engine will not crank over, then there is one simple test which you can quickly perform in order to help you to further isolate the problem.This test will require the help of someone to assist you. What you are going to do is to verify whether or not the required electrical signals are present at the starting motor itself; If they are, then the starting motor is at fault. If not, then we can look elsewhere for the trouble.
To perform this test, you will need to know the exact location of the starting motor on your vehicle. You can get this information in several ways, but the best way is to buy a service manual for your particular vehicle. The service manual is an invaluable aid for many tests and repairs, and is not expensive. You can usually buy them at almost any auto supply store. You will also need something with which to indicate the presence of electrical voltage, such as a DC Voltmeter, Multimeter, or a so-called “Test Light”. Any of these can be purchased at nearly any auto supply store, home improvement store, or large department store such as Wal-Mart®. We will discuss using the test light for this test because it is the easiest to use and the most inexpensive, usually about $5 – 15 USD.
IMPORTANT: Before performing any tests, make sure that the vehicle is securely parked and cannot move. Block wheels if needed. Make sure that the transmission is in Park or Neutral as applicable, and set the parking brake. If it is necessary to raise the vehicle in order to perform this test, then excessive proper safety precautions and use jackstands to support the vehicle. NEVER crawl underneath a vehicle which is only supported by a jack.
The test light will usually look similar to an ice pick with a wire attached. This wire will have a metal clip on the other end. After you have observed the above safety precautions, then perform the following test procedure:
a) Locate the starting motor. Once located, attach the metal clip lead of the test light to a good electrical ground near the starting motor. The attachment point must be bare metal (no paint nor rust), and must be clean and dry. A good place to attach for this might be a bolt or nut on or near the starting motor.
b) Look for and make mental note of any wires which are connected to the starting motor. In most cases there will be one large wire and one smaller wire. The points at which these wires connect to the starting motor are where you will connect the probe (sharp point) of your test light for the rest of this procedure.
c) Have the person who is assisting you climb into the vehicle. Put yourself into position so that you can connect or touch the probe of the test light to the points described above. Once you are in position, have your assistant attempt to start the vehicle whilst you connect the test probe to each of the starting motor wires.
d) While your assistant is attempting to start the engine – i.e. the key is in the start position – the test light should light up when you touch any of the wires at the starting motor. If this is the case, you need not troubleshoot any further. The problem will likely be in the starting motor itself or its attached solenoid. There is one exception to this and that is if the system uses a separate electrical relay for starting such as in some Ford vehicles. If your vehicle has such a relay, it will usually be mounted upon one of the inside fenders, underneath the hood. You can use your test light to test the relay using exactly the same procedure as for the starting motor – with the key in the start position, the two larger wires which are connected to the relay should light up the test light. Again, if this is the case, then the starting motor is at fault.
If the test light does not light under the conditions described above, then further troubleshooting may be required. Another very common cause of starting problems is the safety switch mentioned earlier in this article. The location and testing of the safety switch will be covered in the service manual for your vehicle.
I hope that this article has given an understanding of your vehicle starting system and its associated basic tests.
For a lot more quality and useful car repair information visit the Auto Repair Guide website where you can find good information and resources to help you save money, make informed repair decisions, learn how to do your own repairs, and get the most from your vehicle.
Eldon Jarrard is a certified professional automotive technician who specializes in electrical repairs and driveability diagnostics. Eldon also has over 25 years of experience in the field.
Recent Comments