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New Tech Articles from ImportCar Magazine
Starter Troubles -
Testing For Potential Problems
Edited from an article by Gary Goms, ImportCar, July 2003
When we diagnose problems with the modern, permanent magnet, reduction-gear import starter, let’s begin by looking at a system composed of the battery, starter and connecting wiring. The automotive battery, for example, is designed as a fast-discharge battery capable of sustaining enough amperage output to crank the engine until the fuel injection and ignition cycles take place in the engine’s cylinders. In many cases, we’re seeing batteries being installed in import vehicles that range from the cheap, discount store variety that barely meet OEM specifications to the exotic, high-output units that far exceed those requirements.
Although each design has its own discharge characteristics and failure patterns, cell failure is perhaps the most common issue that affects starter operation and the characteristics of the starter itself. Conventional load testing, therefore, often fails to detect defective battery cells. To perform an accurate load test, the battery must be fully charged and at room temperature.
If the battery isn’t fully charged, test the alternator for output voltage and amperage. Keep in mind that modern load-sensing charging systems, such as those found on many Honda models, may only charge during specific operating modes, such as when the lights are turned on. When the alternator does charge, the voltage should range from about 14.2 cold to about 13.8 hot. Loaded amperage should range from 40 to 60 amperes on a late-model, accessory-laden import.
After verifying charging voltage, the battery must then be loaded to either the test value indicated on the battery label or to one-half the rated cold-cranking amperes (CCA) for 15 seconds. After load testing, a battery that’s in good condition should have at least 9.6 volts remaining at the terminals.
Another method, called conductance testing, reveals cell faults by metering a small alternating current through the battery cells. For conductance testing to be successful, the battery should be load tested or the headlights should be turned on for five minutes to remove the surface charge from the battery. Next, it’s equally important to enter the CCA numerical value rated at 0° F into the tester. Using the "advertised" cranking amps rated at 70 degrees or room temperature will cause a failed reading.
Open circuit voltage (OCV) measurements are also a good indicator of cell condition. A battery that’s in good condition with the surface charge removed should produce 12.6 volts OCV. A 12.4 OCV indicates a 75 percent charge, whereas a 12.2 OCV indicates a
50 percent charge state, and a 12.0 OCV indicates a 25 percent charge. A battery that can’t maintain 12.6 OCV usually has a defective cell or weak electrolyte. High OCVs, such as 12.8, usually indicate that the specific gravity of the electrolyte (normally 1.250-1.270) is too high.
THE CRANKING PROCESS
The starter plays an unusually important role in the modern computerized engine management system because most late-model engines must crank at about 200-300 rpm to activate the electronic fuel injection. For example, when the PCM "sees" a strong, sustained signal from the crankshaft position sensor (CKP), it will activate the fuel pump relay in order to pressurize the fuel injectors. Without seeing a reliable CKP signal indicating sufficient cranking speed, the PCM may not activate the fuel pump relay, thereby creating a cranking, no-start condition.
In the same sense, many imports equipped with air flow sensors or meters must also generate a specific volume of air flow through the meter to close the fuel pump relay. In either case, if the starter fails to spin the engine fast enough for the PCM to activate the fuel pump, the engine will not start.
DIAGNOSTIC OVERVIEW
So, if the engine doesn’t crank fast enough for the PCM to activate the fuel pump relay, which is at fault, the battery or the starter? The answer will be relatively obvious on low-mileage imports that have little wear on the battery, starter, or charging and engine management systems. However, it’s important to remember that the answer is not as easy to discern on high-mileage vehicles due to a larger degree of wear on the starter and other components of the starting system.
As a basic consideration, it’s always important to make sure that battery connections are tight and free of corrosion. Especially integral are the B+ connection to the starter and the B- connection to the engine block and chassis. Too often, these connections are left loose if the engine or transaxle has been removed. It’s also critical to make sure that the battery can deliver sufficient voltage and amperage to the starter.
As for testing the starter itself, begin by checking the engine oil level. Often in today’s self-service gasoline market, the owner simply forgets to check the oil level and runs the engine dry. This mimics a bad starter by seizing the engine bearings to the crankshaft.
The second major step is to determine the nature of the starter failure. A defective starter either fails to engage or cranks too slowly to engage the engine electronics. Engagement failures fall into three varieties. The first failure scenario involves a "zero engagement" or "no-clicking" activation of the starter solenoid. In today’s vehicles, a condition like this can be caused by an unintentional activation of a vehicle anti-theft system. In other cases, a defective ignition switch, starter relay or loose wiring connection can cause the problem.
The most accurate way to test these components is to connect a DVOM to the primary wire connection on the starter solenoid. Using the min./max. feature found on most professional DVOMs or multimeters, record the voltage at the solenoid terminal when turning the ignition switch to the "crank" position. If battery voltage is recorded, the above components should be considered in good condition.
If the starter clicks, but doesn’t engage, the problem is usually caused by a faulty starter solenoid that’s not engaging the starter drive gear. In most cases, replacing starter solenoids is not a cost-effective procedure; replacing the solenoid by itself is very expensive compared to replacing the defective starter with a remanufactured unit.
The second failure scenario occurs when the starter motor is running but fails to engage the flywheel ring gear or when the engagement is rough and noisy. In most of these cases, the overrun or one-way roller clutch on the starter drive gear is worn or sticking. In the remainder of these cases, the flywheel ring gear itself is either worn, or has broken or missing teeth.
The third failure scenario is a low-cranking speed issue caused by worn shaft bushings or a seized engine. In either case, the starter’s amperage draw will be unusually high for the application. Also, when starter current draw is high, remember that battery voltage will often drop below 9.6 volts. This is enough to affect system electronics which, in turn, will affect fuel pump operation.
Finally, keep in mind that simply dropping a permanent magnet starter can fracture a field magnet, which may cause a variety of cranking speed symptoms.
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