Starting System Malfunctions
Nothing is more frustrating than getting behind the wheel, turning the key and not having the car start. This is especially true when you’re in a hurry and there is someplace you need to be. Finding the cause of this no-start condition can be just as frustrating. Anything from a dead battery to a poor ground condition can disable a vehicle. And, as we head into the fall months, approaching winter, it’s a good time to review the causes and solutions to starting system malfunctions.
THE STARTING SYSTEM
The basic starting system consists of the starter relay and the starter motor, with its integral starter solenoid. But there are other components that are considered to be part of the starting system. These include the battery, battery cables, ignition switch, the position switch (clutch pedal or park/neutral switch depending on the type of transmission) and the wire harnesses and connectors.
When a vehicle does not start, the problem can usually be traced to the starter relay, starter motor or the battery. The ignition switch and position switch are not usually at fault. When a vehicle does not start, what is the first component that you check? It’s probably the battery. If there’s no juice, there’s no starting the car regardless of the condition of the other starting system components.
The battery, starting and charging systems operate in conjunction with one another and should be tested as a complete system. When attempting to diagnose a problem with any of these systems, it is important to remember their interdependency.
The diagnostic procedures used include the most basic conventional diagnostic methods to the more sophisticated On-Board Diagnostics (OBD) built into the Powertrain Control Module (PCM). Tools such as an induction-type milliampere ammeter, volt/ohmmeter, battery charger and 12-volt test lamp might be required.
In this article we review basic conventional diagnostic methods for trouble-shooting starting system malfunctions. Quite often, starting difficulties are the result of simple problems within the battery or starting systems. Let’s look at the battery first.
TESTING THE BATTERY
Most batteries installed on late model cars are sealed and maintenance-free. The built-in indicator that provided state-of-charge information is gone, too. Yet, there are plenty of batteries that still use this sight glass. However, before we start testing the battery, it should be inspected.
The importance of the battery terminal cleanliness cannot be overstated, especially if the vehicle is driven in a cold, winter climate. Remove the battery cables and check for any signs of corrosion. The battery posts should be cleaned with a wire brush. The terminal should be cleaned with a terminal brush, as shown in Figure 1. If the corrosion has expanded into the cable wire, replace the cable.
Next, determine the state of charge of the battery. If the battery has a built-in indicator, look into the sight glass. Note the color of the indicator. If the indicator is green, the state-of-charge is 75 to 100 percent, which is adequate. If there is no built-in indicator, a hydrometer can be used. If, however, there are non-removable cell caps and no built-in indicator, a voltmeter can be used.
A battery open-circuit voltage (no load) test will indicate the approximate state-of-charge. First, remove the surface charge by turning on the headlamps for 15 seconds. Next, allow the voltage to stabilize for five minutes. Then, disconnect the battery cables (negative first) and connect the voltmeter. A reading of 12.4 volts or more indicates adequate charge.
STARTING SYSTEM TESTS
Once the state-of-charge of the battery has been determined to be good, a cold-cranking test can be performed. Engage the parking brake. If the vehicle is equipped with an automatic transmission, place the gearshift lever in Park. If the vehicle is equipped with a manual transmission, place the gearshift lever in Neutral and block the clutch pedal in the fully depressed position. Verify that all lamps and accessories are turned off. Finally, to prevent the engine from starting, remove the Automatic Shut Down (ASD) relay.
Connect a volt-ampere test meter to the battery terminals (Figure 2). Rotate and hold the ignition key in the Start position. Note the cranking voltage and current (amperage) draw readings on the volt-ampere tester. Remember, a cold engine will increase the starter current draw and reduce the battery voltage reading.
If the voltage reading is below 9.6 volts, there might be a problem with the starter. Refer to the appropriate test procedures. If the starter motor is good, refer to engine diagnosis and testing procedures. If the starter motor proves to be bad, replace it.
If the voltage reads above 9.6 volts and the current draw reads below specs, perform a feed circuit test. This test is detailed later in this article.
If the voltage reads 12.5 volts or greater and the starter motor does not turn, refer to the appropriate control circuit test.
If the voltage reads 12.5 volts or greater and the starter motor turns very slowly, perform a feed circuit test.
The feed circuit test will determine if there is excessive resistance in the high-amperage starter feed circuit. When performing this test, the voltage drop is giving an indication of resistance between the two points at which the voltmeter probes are attached. The same vehicle conditions apply for this test as for the cold-cranking test. A voltmeter, accurate to 1/10 (0.10) volt, is required.
To perform this test, connect the positive and negative leads of the voltmeter between several points. The first is between the negative battery terminal post (positive lead) and the negative battery cable clamp (negative lead). Rotate and hold the ignition key in the Start position. If voltage is detected, correct the poor contact between the cable clamp and terminal post.
Next, repeat this test, but this time between the positive battery terminal post and the positive battery cable clamp. Rotate and hold the ignition key in the Start position. If voltage is detected, correct the poor contact between the cable clamp and terminal post.
Now, connect the voltmeter to measure the voltage between the positive battery terminal post and the starter solenoid battery terminal stud (this connection is shown in Figure 3). Rotate and hold the ignition key in the Start position. Observe the voltmeter. If the reading is above 0.2 volt, clean and tighten the battery cable connection at the solenoid. Repeat the test. If the voltage reading is unchanged, the positive battery cable is faulty. Replace it.
Next, connect the voltmeter between the negative battery terminal post and a good, clean ground on the engine block. Rotate and hold the ignition key in the Start position. Observe the voltmeter. If the reading is above 0.2 volt, clean and tighten the negative battery cable attachment on the engine block. Repeat the test. If the voltage reading is unchanged, the negative battery cable is faulty. Replace it.
Finally, connect the positive lead of the voltmeter to the starter housing. Connect the negative lead of the voltmeter to the negative battery terminal post. Rotate and hold the ignition key in the Start position. Observe the voltmeter. If the reading is above 0.2 volt, correct the poor starter-to-engine block ground contact.
