JH timing and the Bosch starter

[jdbubb at ix.netcom.com (Dan Bubb)]

Stock K-Jetronic has no control over ignition timing on a JH.

It sure sounds like the ignition is pretty advanced while cranking and is causing kickback.
But, I would think 6 deg BTDC wouldn't be enough to cause that.
So, I'm wondering how your vacuum advance/retard is set up?
The advance is getting ported vacuum? And the throttle plate is adjusted correctly so there isn't
any vacuum advance at idle? Vacuum lines all hooked up per Bentley?
Just throwing some thoughts out since it sounds like alot more advance during cranking than with the
engine idling and the vacuum advance/retard seems like the only thing that might effect that.
HTH.
Dan

----- Original Message -----
From: "Gordon Forbess" <gforbess@attglobal.net>
To: <scirocco-l@scirocco.org>
Sent: Tuesday, December 07, 2004 12:25 AM
Subject: JH timing and the Bosch starter


Here's my question:  Does the K-Jetronic (that's the one, right?)
system that ran the stock JHs retard the timing during the start
cycle?

If so, that might explain the behavior in my completely computerless
carbureted car (which originally came with a motor set at 3 degrees
ATDC).  My motor runs great at 6 degrees advanced (recently reset from
about +2 degrees) and I've checked it twice after a drive to make sure
it's spot on the mark on the flywheel.

The nasty behavior is that the starter now "bogs" on the initial try
and stops.  Often, just trying it again will start the motor, but the
"bog" is still there.  I'm thinking with the 6 degrees advanced
timing,  it is firing on the compression stroke and fighting the
starter motor.

Another clue:  If I cut my "secret kill switch" (which interrupts 12v
to the coil) and crank the motor, the starter spins it very fast.
Then quickly flipping the switch back to the "run" position while
still cranking, the motor fires normally.  No bogging down at all.

To eliminate other possible problems, I have recently replaced both
battery cables, the ground from alternator to block and added another
ground from the alt case to the body.  Also checked and cleaned all
connections.  In addition, I've added a relay to supply the starter
solenoid circuit so it doesn't let go when the voltage drops when the
starter motor gets powered. (This is evidently a problem well known on
certain Bosch starters and VW actually sells a kit with relay and
wiring harness)   The battery is nearly new, is fully charged and my
voltmeter says the charging circuit is working well.





Gordon
75 Scirocco/Drake 1.9 8V
http://pws.prserv.net/scirocco/scirocco.htm

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