The starter motor is what sealed the
fate of early
electric cars.
Ironically, electric cars inspired the starter motor. Early gas cars were grand and fast, but unpopular, since starting them usually involved one person in the driver's seat adjusting the
spark and
gas while someone standing in front of the car (with one arm
honed to
muscular perfection) spun the whole engine by hand with a
crank. And there was always the chance of a
backfire breaking said person's arm.
Yes, most early cars were electric because it was
convenient and it worked.
Ambulances were even electric. Then gas cars borrowed a trick from electric cars, namely the
motor and
battery. Someone
bolted the motor to the
engine in a way that it would rotate the
flywheel at a suitable starting
RPM. Use the battery to power the motor and provide spark, and
presto, electric cars were forgotten for
decades. Gas powered cars could now be started easily by anybody.
There are two types of modern starter motors I've seen:
Ones with attached
solenoids and ones without.
Starters without attached solenoids usually only have one wire going to them, a thick
high amp wire coming from the
starter relay (and a
ground, of course). They are
geared so that when
activiated the motor
shaft will spin within the pinion which causes it extend long enough to contact the
engine's
flywheel and spin the engine. When the starter motor stops the still-spinning pinion spins back down the motor shaft away from the flywheel.
I've noticed these type to be a bit more
reliable and safer to work with.
Starters with an attached
solenoid look just like a normal starter but with a
cylinder stuck to the side, near the pinion. These type have two wires, a
live high amp wire from the battery and a smaller wire from the starter
switch. The small wire
activates the solenoid, which connects the high amp wire to the starter motor while also (usually, your starter may vary) extending the pinion along the starter motor's shaft into contact with the flywheel. This is great, but...
Make
DAMN SURE you unhook the
battery when changing this type of starter. Since there's no starter relay to turn off that hot wire, it is always
live and will
weld itself to the
frame,
oil pan, or whatever you touch it to.
Also, these types don't seem to wear as well. Especially on trucks and big engines that don't have much stuff around the starter to shield from water splashes and road
muck. Since the solenoid is in charge of engaging the motor to the engine, there’s more moving parts to break and wear down.
I've replaced my solenoid-based starter twice in two years. Last time it decided it was going to keep trying to start, regardless of what position the key was in. If yours does this, TURN THE KEY OFF. The solenoid is probably stuck and the starter will burn out and/or eat up your flywheel. Then quickly unplug the battery. Try lightly hitting the solenoid with something. For my
F-150 I stuck a long wooden dowel alongside the engine and tapped it through the hood. That will usually free up the solenoid (you will sometimes hear a 'clunk' sound when that happens), now you can start it and drive to the
auto shop to get a new one. Sometimes you can get the solenoid by itself, but you'll probably be stuck buying a whole new starter.