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Diagnosing Starter Problems

You turn the ignition key and you get that dreaded clicking sound. Or maybe after a few seconds of cranking, without starting, the starter runs very sluggishly. In either case, you now have a starting system problem.

A couple of cautions when experiencing starting system problems. You can damage a starter by continuous cranking because the starter heats up very rapidly. After cranking for a half minute, let it rest for a couple minutes to cool off a bit. If the engine doesn't turn over after a few tries, find the source of the problem. The starting system is probably not the culprit especially if problems start with a drastic drop in temperature. Check the car for ignition or fuel system faults.

Many of us immediately reach for the jumper cables when a vehicle will not start. If the crankcase oil is like molasses, or the engine is tight or seized, the engine cannot crank fast enough, even with normal battery amperage. Boosting from another source provides additional amperage that can damage the starter.

Be especially cautious when jump starting a modern car with electronics and computers onboard. Electronic components are very vulnerable to voltage spikes. Indeed, before jump starting a late model vehicle, read the owners manuals. New car have specific instructions for jump starting, if you can even do it.

You can do a few tests to diagnose a starting system problem without any tools or measuring equipment. Turn on the headlights and start cranking. If lights go out, you probably have a poor battery cable connection that is impeeding the flow of current. Start checking battery posts and battery cables for tightness and corrosion. A very thin film of oxide between the terminal and cable clamp can choke off most of current. Clean battery posts and cable terminals. Make sure all connections are tight. Also check connections to the starter and solenoid and engine-to-chassis grounding cables.

If headlights continue to shine brightly and nothing happens, voltage is probably not reaching the starter. Usual suspects here include a problem with the park/neutral or ignition circuit switches.

If lights go dim and the cranking action is sluggish, first suspect a low battery.

Starting problems especially in cold weather on a system that worked well last summer can often be traced to a weak battery. Sub-zero temperatures can cut a battery's amperage output by more than half. Check out the battery condition. If the battery checks out okay, look for a locked or dragging starter, a starter with high internal resistance, worn brushes or open circuits in starter's windings or armature.

You can use a multimeter to check for starter problems. A starter current draw test should be performed to see if you have to replace the starter Measure the amperage on the battery-to-starter cable while cranking the engine. As a general rule of thumb, under normal load conditions, the starter should draw about one ampere per cubic inch of engine displacement, plus or minus about 25-percent. Check the service manual for the specifications for your particular vehicle.

If the current draw is not too high, check for resistance in the starter circuit. Starter current can exceed 200A, even 300A on large displacement engines, so even low resistance can cause a significant voltage drop. Rather than measure resistance, which is usually off scale for most DMMs, measure the current drop instead. A drop of only 0.2 to 0.3 volts may be enough to reduce performance in automotive circuits. Set the DMM to the millivolt scale and connect the positive lead to the side of the component nearest the battery (+) and the negative lead to the Systematically, check drop between battery post and connecting cable, the solenoid posts and wires that attach to them and across the solenoid itself. Also check connections to the starter, alternator and ground strap link the engine block and body.

Normal Voltage Drops
Across wires or cables 200 mV
Across switches 300 mV
Grounds 100 mV
Connectors 0 mV

If the battery cables are damaged or have worn insulation, replace them. Spend a few extra bucks and get the best quality ones. Cheap one may look okay from the outside, but may be made with small gauge wire covered by thick insulation. These undersized cables cannot carry the peak current when needed.

A "click" with no cranking probably means the solenoid is being energized but there is not enough current to turn the starter over. You can check for a faulty solenoid by bypassing it. If the starter now spins, the solenoid is probably bad. If the starter spins, but it will not crank the engine, check for an engagement problem. The latter could be caused by a weak solenoid, defective starter drive or broken teeth on the flywheel. A starter on the verge of failure may engage, but slip. Incidently, if the starter locks ups while engaged with the flywheel, it can over rev the starter destroying it.

Then there is the matter of noises emitted by the starter system. A high pitch whine could be caused by misalignment of the starter. Check also for nuts and bolts that might have vibrated loose.

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