Ignition troubleshooting on a Mk.1 (v. long)

[MK1Scirocco16v at comcast.net (Dave Ewing)]

I like to use a very simple tool to rule out the ignition switch--a known
good ignition assy with a switch in it.  This way you just unplug your
switch, hook it to the test switch and turn.  You can do this just with a
switch and a screw driver.  The switch is what I would check first as they
are a common faulty item.  I wouldn't suspect the coil.  BTW, are you
measuring resistance with the wires attached??

Usually when the modules go bad they will be irratic meaning that it will
die then start back up and run like nothing happened until it dies again.
If the Hall sender goes bad it won't play games with you like the
module--they usually just die unless there is a bad wire that gets knocked
around.

HTH!

Dave
----- Original Message ----- 
From: "Ben Channard" <zeroid@hotmail.com>
To: <scirocco-l@scirocco.org>
Sent: Monday, September 08, 2003 7:56 PM
Subject: Ignition troubleshooting on a Mk.1 (v. long)


> Abstract:  Have fuel but no spark.  Battery and starter are good.
>
> My CIS 1981 Mk.1 wouldn't start one evening.  To my surprise, It started
and
> restarted the next morning but when I finally wanted to drive away an hour
> later, it wouldn't start.  Fuel pump buzzes and jumpering the fuel pump
> relay doesn't remedy, and I can smell fuel so I've focused on ignition.
>
> I followed the Bentley (R/S/J '80-'84) ignition troubleshooting protocol
but
> have several ambiguous results and am still left with a non-starting car.
>
> To test the coil for spark the Bentley calls for a 1000 ohm suppression
> resistance at "each end of the cable" but I'm not sure how to set this up.
> I tried the test without a resistor and saw nothing.  Also saw no spark at
a
> grounded spark plug.
>
> Tested the coil's resistance between the center electrode (#4) and
terminal
> 1and got a reading of 4.2K ohms which is within range but the reading
> between terminals 1 & 15 was 0.9 to 1.0 ohm which is outside the
acceptable
> range of 0.52 to 0.76 ohms.  Thinking this was the culprit, I bought a new
> coil (Niehoff brand) and ignition was still dead.  The new coil also had a
> resistance of 1.0 ohms between terminals 1 & 15!  Is this coil bad?
>
> Voltage at terminals 2 & 4 of the ignition module harness is 12.1V which
is
> OK.  (As an aside, the photos for Fig 4-4 and 4-5 are switched in my
seventh
> revised edition of my Bentley).
>
> Tested the ignition module by detaching the distributor harness and
> measuring voltage at terminals 1 & 15 of the coil.  Turning on the
ignition
> gave a constant 0.56V instead of the 2 volt or above which should fall to
> zero after a couple seconds.
>
> Ignition module seems bad so I tried two other boneyard modules and they
> don't work and in fact give no voltage with the above test.
>
> Tested the Hall sender by measuring voltage at terminals 3 & 6 of the
> ignition module while hand turning the crank--voltage alternated between
> 3.03V and zero which is normal.  BTW, the car died while driving about a
> week and half ago due to a broken Hall sender wire.  Replaced the sender
> with a used one and car started up fine.  The pin which anchors the
trigger
> wheel to the shaft fell out when trying to lever out the wheel.  Can this
> pin cause problems since it fell into the distributor body?
>
> Other miscellaneous checks--all three wires from the distributor harness
had
> continuity to the ignition module.
>
> Can the oxygen sensor box cause a no start?  How about the ignition switch
> even though the fuel pump and starter and all electricals are activated by
> the key?  Can I rule out the distributor?
>
> Can the new coil be bad?  Is it likely that all three ignition modules are
> bad (albeit they are all used)?   I'm leaning toward the ignition module
but
> I'd like to eliminate any likely suspects before springing for a new
module.
>   Thanks for slogging through this email.  Regards, benton-----
>
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