Date: Tue, 23 Dec 2014 08:49:56 -0800
Reply-To: Stuart MacMillan <stuartmacm@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stuart MacMillan <stuartmacm@GMAIL.COM>
Subject: Re: Trying to understand starter stuff
In-Reply-To: <vanagon%2014122300460061@GERRY.VANAGON.COM>
Content-Type: text/plain; charset="us-ascii"
Here is a nice relay setup:
http://www.thesamba.com/vw/classifieds/detail.php?id=1119534 (Won't work
with an automatic with factory cruise control for some reason though.)
Stuart
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
David Beierl
Sent: Monday, December 22, 2014 9:46 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Trying to understand starter stuff
At 11:03 PM 12/22/2014, Marc Perdue wrote:
>Hi all,
Excellent! I now have three verified cases of a starter control lead coming
off without causing a hard start failure: your Van, my '89 2.1l, and my '71
Fiat 128. I solved that one after running out of gas in an uphill line to
buy gas somwehere in upstate New York, when it became clear that the motor
would crank if it were torqued slightly sideways.
Starters have some challenging necessities. They have to have big cables
direct to the battery; a heavy switch that can switch them on and off under
load without burning up quickly; a means of engaging the pinion into the
flywheel ring gear; and a positive means of disengaging it when the motor
starts, so the starter doesn't burst from overspeed.
Back when the world was new the electrical switching was done by a
heavy-duty relay that would today be called a contactor but was commonly
known as a solenoid. It was mounted somewhere between battery and starter,
and a light wire from the starter button or key switch used to activate it.
For testing you could use a screwdriver to jumper between the big battery
cable connection and the control terminal. Starter "solenoids" were a
commonly available FLAPS part and no doubt still are; as they regularly
failed in use. Last one I bought cost three or four dollars. Excellent for
switching a couple hundred amps DC but not rated for continuous duty.
They're meant for starting cars, once per trip segment, plenty of time to
cool in between.
Engaging and disengaging the pinion was accomplished by a clever invention
called a Bendix drive. The pinion was mounted on the starter shaft and
engaged a pair of helical slots in the shaft. It was kept wound down to the
bottoms of the slots by a light spring that pressed it away from the end of
the shaft. When you hit the button, the shaft would spin violently and hurl
the pinion into engagement during the first few revolutions. And when the
motor started, the ring gear would spin the pinion back down the track out
of engagement. It worked a treat, so long as you kept it clean and not
gucked up with oik or grease. The Bendix Corporation waxed fat and happy.
Came the day that someone thought it would be better to combine actions. If
the contactor were mounted on the starter it would simplify wiring, and it
could be used as a real solenoid, to physically throw the pinion into
engagement as well. Or rather a solenoid could be thus used, and with some
contacts added could perform the contactor function as well. An overrunning
clutch would handle decoupling the starter from the engine, leaving the
pinion in engagement but not forcing the starter to keep up with it. Full
disengagement would happen when the key was released. Over a decade or two
this method largely took over for starting cars, and that's how Bosch did it
on our starters.
The big cable goes direct from battery to starter, where it meets the
thinner wire from the alternator that supplies charge. That connection is
subject to corrosion. The ground connection through the starter, bell
housing, transmission ground strap may be defective. The solenoid itself
wears and gets crudded up; you have to take the starter apart to clean it
up. Non-A/T versions of this starter have no bearing at the pinion end; the
shaft inserts into a sleeve bearing that's in turn inserted into the bell
housing of the engine. That wears and needs renewal. And the solenoid gets
its operating power not from that fat cable but from battery to panel to
ignition switch and back to the starter. It only needs two or three amps,
but it's a long trip. It's easy to see if a relay could help it -- just
jumper the alternator B+ post to the starter control terminal. You can
reach it by reaching your hand over the top of the bell housing, quite a way
forward and then to the right. There's probably a spare terminal to latch
on to. If it cranks snappily that way and listlessly by the key, add a
relay. If it makes no difference, neither will the relay.
Yours,
David
