Re: Cold start valve/thermo time switch testing (cold startingproblems)

["Victor Farren" <vfarren@rrs.cdie.org>]

Looks like a good write up to put on Scirocco.org. 

>>> "Andre' Bjorkheim" <andreb.mail@gte.net> 09/22 7:28 PM >>>
Helpful test for checking functionality of the cold start and the
thermo time switch unit.  I believe its applicable to both Mk1 and Mk2
roccos.  This came about because the 75-79 Bentley had the incorrect
procedure (regarding wiring) for testing the cold start unit.  Perhaps
this will help some of you listees in fixing your cold start problems.

    If you have a meter, some wire, and basic tools you can do it ALL 
the cold start/thermo time switch testing yourself.  

  First thing I would suggest is running an extra ground wire from
where the cold start bolts up to either the chassis or the battery
ground itself.  On my Mk1 its not necessary, but for some reason I 
have heard that it is a problem with the Mk2 cars.  Also clean your
battery ground cable and where it bolts up to the battery and also the
chassis.

  Second, if you have a multimeter you can test to see if both the
thermo time switch and the cold start are getting power when you
crank the engine over.  To do this, simply remove the 12 guage wire
(red w/blk stripe) off of terminal 50 on the starter.  This is the
wire that gets power when you crank the car over.  Also remove the
plugs on the thermo time switch and the cold start valve.  Take the
multimeter and check for continuity between the 12 guage red w/blk
wire that goes to the starter solenoid with the red w/blk wires
that go to the cold start and thermo time switch.  In each case, 
you should read close to 0 ohms.  If either of those red w/blk 
wires that goes to the cold start or thermo time are busted, then
they arent getting power on cranking, and hence cold starting will
be a problem.  

  Next, if those wires check out okay, you will need to check the
continuity between the green w/white stripe wire.  This wire is 
connects the cold start to the thermo time switch.  When the car
is cold, the thermo time switch grounds that wire so the cold
start will then fire.  If the circuit is open, the cold start will
never fire.

  Next, if that wire checks out okay (roughly 0 ohms resistance)
then you will want to check the operation of the thermo switch
and cold start valve themselves.  To do so, simply take the meter
and read the resistance between the one spade terminal on the
thermo switch that corresponds to the green w/white wire and the 
engine block.  When cold (recommended you do it in the morning)
this resistance should be very low, if not zero.  When hot it
will read a few hundred ohms or more.

  To check the operation of the cold start, simply ground the
green w/white wire (keeping the plug attached to the cold start
while grounding the green w/wht wire from the thermo time switch 
plug) and try to crank the engine over.  If everything is peachy, 
meaning the cold starts red w/blk wire had power and the green
w/white wire is properly grounded) and the car should fire right
up.  If not, then the cold start isnt functioning.  If it
doesnt fire right up, you can take the cold start off the
end of the intake manifold, place it into a jar, remove the
12 guage red w/blk wire from the starter solenoid, place a 
jumper wire from the battery + into the red w/blk wire and
then jumper L13 and L14 where the fuel pump relay sits (or 
terminal 87-output and 30-power on where the relay sits), and
you should get fuel to spray out.  If not, then your cold 
start is faulty.

  I hope this solves your cold start problem.  And, if I missed
anything, I hope someone points it out to me.  Good luck...  

==============================================

 André Bjorkheim 
 Lime Green 79 Scirocco ©
 ICQ #76283458

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