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Before an engine will start, it must first be cranked. Turning the engine over draws air and fuel into the cylinders
and compresses the mixture so it can be ignited to provide power. Cranking the engine also generates the ignition
and crankshaft position sensor signals that are needed to fire the spark plugs and operate the fuel injectors.
So if a starter fails to crank the engine or turns too slowly, the engine won’t start. And a no-start means the
vehicle owner either walks or bums rides until the problem is fixed (unless, of course, he’s a real plugger who
drives a vehicle with a stick shift and enjoys the thrill of pushing or roll starting his vehicle.
Starting problems can be a real headache because of the uncertainty and frustration they create. Most people won’t
tolerate a starting problem for long, and will seek out repairs or try to fix the problem themselves (if they’re
a do-it-yourselfer) - which means somebody has to diagnosis what’s causing the starting problem and then make the
necessary repairs.
Unfortunately, starting problems aren’t always simple to diagnose. Sometimes the starter motor is blamed for a
hard starting or no-start condition that is not the starter’s fault. As a result, some starters are replaced unnecessarily.
But when the newly installed starter fails to work any better than the old starter, your customer thinks the one
you sold his is no good and brings it back. Then you’ve got an angry customer in your face, and you’re in the awkward
position of trying to figure out what (or who) is really at fault.
One way to avoid such predicaments is to bench test old starters to make sure they are defective before you sell
your customer a replacement.
IS IT REALLY THE STARTER? Any one of a number of things can prevent an engine from starting. An engine needs the
right combination of air, fuel, compression and ignition to start. If any of these is lacking, the engine may be
hard to start or not start at all.
If nothing happens when the ignition switch is turned to the start position, it may mean the starter motor has
failed, or there may be an open in the ignition switch, starter circuit wiring or neutral safety switch on the
transmission linkage. Some vehicles with manual transmissions also have a safety switch on the clutch pedal that
prevents the starter from cranking unless the clutch pedal is depressed. Other causes of no cranking may include
a bad solenoid, loose or corroded battery cables or even a low or dead battery.
The first thing that should always be inspected is the battery to make sure it has enough voltage to operate the
starter. A discharged battery or one that is badly sulfated may not be capable of producing enough voltage or amps
to start the engine.
The next check would be the starter motor itself. Using a jumper to bypass the solenoid is a trick that will show
if the starter motor spins or not. If the starter works when bypassing the solenoid, the problem is in the solenoid
or ignition circuit.
If an engine cranks at normal speed but refuses to start, it’s probably not the starter - unless the starter motor
is pulling so many amps from the battery that there isn’t enough voltage left to power the ignition system and
fuel injectors.
A good starter will normally draw 60 to 150 amps with no load on it, and up to 250 amps under load (while cranking
the engine). The no-load amp draw depends on the design of the starter, so always refer to the motor’s amp specifications
when bench testing a starter.
If the drive gear mechanism can be replaced separately, there’s no need to replace the entire starter - only the
drive mechanism (which is often referred to as a "Bendix" drive). This is not recommended on permanent
magnet gear reduction starter motors. If faulty, the entire starter should be replaced.
A bad solenoid can also be a source of starter problems. The solenoid acts like a relay to route power directly
to the starter from the battery. It may be mounted on the starter or located elsewhere in the engine compartment
and is usually connected to the positive battery cable. Corrosion, poor ground at the solenoid mount, or poor battery
cable connections will prevent the solenoid from doing its job. Replacement is necessary if the solenoid is defective
or stuck open or closed.
INSIDE THE STARTER. The starter motor itself is a high torque direct current electric motor. Inside are a rotating
armature, four brushes and a pair of field coils or permanent magnets (on new models). The starter uses the opposing
magnetic forces of the armature and field coils or permanent magnets to convert electrical energy into mechanical
energy.
When the ignition switch is turned to the start (crank) position, voltage is routed through a solenoid or relay
to the starter motor. As the starter motor begins to spin, the drive gear extends and engages the teeth on the
flywheel ring gear to crank the engine. When the engine starts and the key is released, the drive gear retracts
and the starter stops spinning. An overrunning clutch in the starter drive prevents the starter from being over-revved
and being damaged when the engine starts.
Though most starters are "direct drive," some have an extra set of reduction gears to increase cranking
torque. Reduction gears also allow a smaller, higher speed motor to be used. Reduction gear starters are often
found on Chrysler and import applications.
Cranking an engine is hard work and pulls a lot of amps out of the battery. The cranking load is even greater during
cold weather because low temperatures thicken the viscosity of the oil in the crankcase and increase drag. At the
same time, the battery has less amps available because cold temperature slows down the chemical processes inside
the battery that release stored electrical power. So if the starter has worn internal components, a poor ground
or positive cable connection with the battery, or the battery’s level of charge is low, the engine may not crank
fast enough to start or it may not crank at all.
Starter problems can be caused by worn brushes (carbon pads inside the motor that supply current to the rotating
armature), by shorts or opens in the armature or field coils or by worn bushings that increase drag or allow the
armature shaft to rub against the pole shoes.
Continuous and prolonged cranking is very hard on a starter because it generates excessive heat. If not allowed
to cool every 30 seconds or so for at least a couple of minutes, the starter will be damaged by continuous cranking.
Fuel injection has reduced the strain on starters because it takes fewer cranks for the engine to start. Consequently,
starter sales for newer vehicles with fuel injection are much lower than those for older vehicles with carbureted
engines.
SELLING TIPS. When a customer needs a starter, the replacement should have the same or higher cranking capacity
as the original. Most quality replacement starters meet this criteria, but some may not because of over-consolidation.
Just because a starter fits a particular vehicle application doesn’t mean it has enough muscle for reliable cold
starting. So in addition to matching bolt patterns, drive gears and electrical connections, it’s also important
to match power ratings, too.
To receive proper core credit for an exchange starter, make sure the old starter is complete and is the correct
one for the application. Reduction gear starters and permanent magnet starters usually have significantly higher
core values. Also, be careful when handling permanent magnet starters because the magnets are brittle and can be
easily cracked.
One item you should also recommend replacing along with the starter on older high mileage vehicles is the solenoid
(if not included with the replacement starter). Solenoids wear too, so replacing this component will help assure
reliable starting.
Your customer might also need new battery cables if the old ones are damaged or badly corroded. It’s important
to make sure the replacement cables are heavy enough to handle the amp load because some inexpensive battery cables
use undersized wires to reduce cost.
The smaller the diameter of the wire, the fewer the amps it can carry. New ground straps may also be needed if
the original straps are missing or damaged.
Lastly, a more powerful battery with a higher cold cranking amps (CCA) rating may provide some added kick for reliable
cold-weather starting. The average battery only last about four years, so if the original battery is more than
four years old, chances are it may need to be replaced.
If the vehicle also has any weaknesses in the charging system, these problems should be addressed too when the
starter is replaced.
FORKLIFT
OPERATION AND SERVICE.
BE SURE TO VISIT THE HOME PAGE FOR INFORMATION ON LIFT TRUCKS REPAIR,
SERVICE, TROUBLESHOOTING, AND EVERYTHING YOU NEED TO KNOW ABOUT FORKLIFTS AND THEIR USE.
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