Regarding using an additional (jumper) battery to help start a vehicle. Tired,
You are not actually increasing the voltage. You ARE increasing the available
amperage ( 1 amp = 1 coulomb/sec or 6.25 billion billion electron/sec) With the
increased available amperage, the batteries (in parallel) are able to maintain
a higher cranking voltage (that which pushes the electrons) ( if you were to
measure voltage at the battery while you were cranking, the reading could be
11.0 volts or less. The additional battery keeps it at or near this level
longer. Without the 'booster', voltage could very quickly drop below 10 volts.
This also helps to explain why a slow crank is often associated with a 'hard
start'. There may not be enough voltage left to create a quality spark in the
coil, especially with tired plugs or worn points)
Another point to consider is that the slower a typical starter turns, the
HIGHER its amp requirements as the starter is, in effect, almost shorted to
ground (through the armature and field coils-the parts that do the work)
With an additional battery hooked in parallel ( jumped + to +, - to - like we
all do) the battery gets 'sucked' down slower, helping to maintain both a
higher cranking speed AND a longer cranking period.
Of course, if the starter is good, and all the connections are sound, this is
just for clarification ;-)
Automotive instructor: Licensed Technician
Stellarton Nova Scotia
>>> "Thomas Walter" <email@example.com> 06/22/00 10:02AM >>>
> I am reassembling a project from boxes. I have a starter that I plan to use
> in 68 2000. Is there an easy way to bench test the starter to see if it is
> any good??
I'd confirm the starter at least spins!
While wearing boots, I will step down on the starter holding
it against the garage floor. Battery cable hooked up from the
mounting ear to "-" side of the battery. Positive cable hooked
up to were the power is normally supplied.
With a "remote starter" between the "+" terminal and 1/4" spade
connection on the stator solenoid, depress the remote starter
button. You should see the pinion gear slide forward, and hear
the starter "whirrrrlllll". Don't let the starter run more than
a few seconds in this unloaded condition.
Ma Roadster (Suze), who hasn't been on this list in years, would
clamp the starter down on her bench, and lift a long piece of
2x4 board into the starter teeth. This was the "load test" she
did. Yes, wood splinters every where!
When the starter brushes get towards the end of their life
you'll discover a slow cranking starter. There are four brushes.
Two positive, two negative. Typically one will fail first, so
rather than having TWO sets of windings to spin the motor,
you only have ONE set of windings energized. Slow spin, but
sometimes a jumped battery seems to start it right up. Battery
is fine, just the jump helped raise the voltage momentarily!
With the starter out, I will remove the back cover, and inspect
the brushes. Typically I can buy four brushes from a rebuild
place for $4 total. Cheap insurance to replace them, and inspect
everything else. Oh, Nissan wants something like $14 each for
Also while everything is out, check the bolt threads into the
bell housing. It is easy to strip the aluminum threads out, and
usually I'll install stainless steel inserts while I have the
starter out. Little things that make life easier.