FI diagnostic plug

[jadney@vwtype3.org (Melissa & Jim)]

>From: Toby Erkson <Toby_Erkson@ccm2.hf.intel.com>

>I have been waiting for someone to mention this, hoping that I wasn't the 
>only one who had it.  I'm referring to the diagnostic plug.  My baby came 
>stock with it (now that my FI system is gone I no longer have it, of 
>course).
>
>Has anyone sat down and figured out a way to use the existing plug to 
>perform system checks.  I mean, if it's there why not use it?  I gave the 
>Bentley manual a cursory look and saw that the electrical diagram shows the 
>connections from the FI and ignition system to the plug so one would think 
>you could use it for home mechanic diagnostics.

There's actually no connection in the diagnostic plug that connects to the 
FI; well, on some years, there is one that makes a common connection to one 
of the starter solenoid terminals where the FI also attaches, but that 
doesn't really count.

Using a diagnostic plug scavanged from a T1, I made a box that that will 
plug into any other diagnostic socket.  From it I can test the dwell, start 
(71-2 only) and crank the engine, and turn on the turn signals and brake 
lights.  It also has LEDs to indicate +12 V and AT kickdown switch 
operation.  I find that this box is only really useful to crank an engine to 
set the dwell when I am working alone, since I don't own one of those remote 
starter switches.

NOTE: this plug was started in late 71, and the 71-2 cars have two wires 
running from it to the starter solenoid.  On those cars only, it is easy for 
someone to reverse the connections at the starter.  This results in the FI 
thinking the starter is cranking all the time the car is running, and makes 
the car run WAY too rich.  The obvious symptom of this is that if you get in 
your car and just turn the key ON, you should hear a relay click and then 
"unclick" about 1 second later.  If you don't hear that second click, those 
wires are reversed (if there are two), or connected to the wrong terminal 
(if you have only one.)  This is mentioned in the Bentley manual.

Jim
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       Melissa Kepner                                    Jim Adney
       jadney@vwtype3.org               jradney@njackn.com
                             Laura Kepner-Adney
                             Madison, Wisconsin
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