On Mon, 27 Dec 93 sfisher@megatest.com (Scott Fisher) wrote:
> Well, it's almost all back together -- the Green Car, that is.
Stuff edited [FL]
>- --Scott "I just hate having to redo work, though" Fisher
OK! Here we go again:
The solenoid on the starter Scott Fisher describes has TWO windings.
Both windings are energized from the starting contacts on the
ignition switch when you turn the key to the starting position.
Winding #1 is connected in series with the starter motor itself. That
is, the current that comes from your ignition switch has to travel
through the winding in the solenoid, through one pair of the brushes,
through the commutator, through the armature, through the other pair
of brushes, through the field windings and, through the ground of the
of the starter, through the ground of the engine, through the ground
strap between the engine and the chassis (or through the choke cable,
if you forgot to put the ground strap back in the last time you pulled
out the engine!) then through the chassis and, finally, through the
negative battery cable back to the battery.
If the brushes do not make proper contact with the armature, chances
are that you will hear a _click_ (or nothing at all) instead of a
_CLICK_ when you turn the key.
Winding #1 is the one which does most of the work of engaging the
pinion with the gear on the flywheel when you turn the switch. This
winding is shorted out by the solenoid contacts when the starter is
engaged. The contacts then supply the full amount juice from the big
fat cable connected to the battery (and back to the battery as described
above).
Winding #2 now is left to itself to keep the starter engaged until you
release the ignition key.
> On this starter, all wires connect to one post of the solenoid; the one
> that matters most is the battery cable. A couple of brown wires bolt to
> that post too, and a white-brown wire connects to a spade lug and runs
> to the ignition switch. That all works; all the ignition-related stuff
> (lights, fuel pump, etc) work when I turn the key.
The big fat wire from the battery supplies the juice from the battery to
the starter when you turn the key. Of the other wires connected to the
same post, one comes from the generator/alternator (through the ammeter,
if you've got one), the other runs to the ignition switch through
the fuse box. Basically this terminal is the hottest point, electrically
speaking, of the entire car. The white-brown wire is the one that supplies
juice to the solenoid winding_s_, as described earlier.
Here's how I would go about troubleshooting your problem:
1. Pull out the starter. Mount the starter in a vice on your workbench.
2. Connect the body of the starter to the negative side of a good
battery, using a jumper cable.
3. Connect a cable between the positive side of the battery to the
small terminal on the solenoid (where the white-brown wire was).
The solenoid should pull in with a good, solid CLICK and stay
in that position until you disconnect the cable.
4. Connect the cable from the positive side of the battery to the
_other_ large terminal on the solenoid (not the one you removed
the battery cable from, but the one closer to the starter itself).
The starter should run freely, without the drive pinion being in
the extended position. Don't do this for more than a few seconds!
5. Finally, connect the positive cable to the top terminal on the
solenoid, run a third wire to the small terminal on the solenoid.
The solenoid should now pull in, extend the drive pinion, close the
contacts and the motor should be spinning. Again, don't do this for
more than a few seconds at a time!
If any of these tests fail, you'll need to rebuild the starter. Since you
already have the starter out, why not rebuild anyway?
Here are a couple of things to keep in mind, if you decide to take the
starter apart:
1. Mark the location of the end plates relative to the starter body with
a couple of center punch marks before you dismantle the starter.
Some starters have little tabs and notches where these parts go
together, some don't. It's important that these parts get put back
in the same place, relative to each other, as they were.
2. Mark the top of the solenoid before you remove it. If you put it
back the wrong way, it won't work.
3. Don't use emery cloth or any other kind of abrasive material on the
commutator. If it needs cleaning or turning, take it to a shop.
> I suppose the next step would be to check resistance across the two
> poles of the solenoid and compare that against resistance from the
> input pole ofthe solenoid to ground on the block. I guess I should
> have asked Santa for a DMM... :-)
Although I have probably half a dozen DMM's, I find it easier to us an
_analog_ voltmeter when working on cars (and boats). My favorite was a
Simpson, model 260-7, which I unfortunately loaned to a fellow SOL'er
a few years ago, and never got back.
(Mike Zwijacz (Lotus Europa). I'm still pissed off at you for that.)
A simple gadget which I find very helpful when troubleshooting 12 volt
circuits is an old taillight with a 25 watt lamp in it. I have connected
two black wires with alligator clips on one side of the lamp. One wire is
about six inches long and is useful for hanging the thing from anything
that is grounded, that's nearby. The other black wire is about 20 feet
long and is used for testing grounding problems, e.g. to test that dim
taillight, I connect the short wire directly to the negative side of the
battery and connect the long wire to the socket of the dim taillight. If
the taillight gets brighter, I know that there is a bad ground somewhere
between the battery and the taillight. On the other side of my test lamp
I have a 20 foot red wire with a pointed test probe on the end. If I
connect this probe to the hot terminal of the same dim taillight as
before and the dim light gets dimmer, I know that there is a problem
between the hot side of the battery and the taillight circuit (The
additional current drawn by the test lamp = additional voltage drop).
The test lamp is also handy for testing corroded fuse holders, flaky
starter switch contacts etc., where a Digital Multimeter may happily
show 12 volts even though there may be hundreds of ohms of resistance
the circuit.
(One modification I would include next time I make one of these gadgets,
would be to include a couple of 10 amp in-line fuses in each of the long
cables.)
> On the assumption that the battery might simply be too pooped to run the
> starter even if it would run the fuel pump and the lights, we backed the
> car out into the driveway (after verifying that the engine wasn't frozen)
> and hooked it up to the ZX, which has a voltmeter. (That, BTW, is about
> the limit of my electrical troubleshooting gear.) I let the ZX charge
> on the B's battery for a few minutes, then tried the M.G.'s key again.
> Still nothing. And furthermore, the voltmeter in the ZX didn't even
> wobble when I turned the B's key to Start.
A voltmeter in a car (even in a ZX, whatever make of LJC that may be) is
not a very good instrument for troubleshooting. A simple test lamp like
the one I just described would work much better. If you hook it up
directly across the battery you'll be able to tell, fairly accurately,
what condition the battery is in, both under load and no-load. If the
light goes from bright to close to nothing when you crank the starter,
well let's hope that Sears is having a sale on DieHards this week. If the
brightness of the lamp changes only slightly, then the battery is most
likely not the problem.
> Oh well. At least now I know how to install the starter and which
> bolt goes where.
Good luck!
- --Flemming "electricity is just like water 'cept you can't see it" Larsen
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