[T3] ? on dist drive

[Jim Adney]

On 16 Aug 2016 at 20:19, William J wrote:

>  What about pin 17 ? There are three wipers or slidding contacts . One that 
> that runs on 12 and 14 and 17 . On decell the forked switch is the contact 
> on accel the forked switch position contacts for the full load .

17, as you suspected, controls the shutoff during coastdown 
(overrun.) The double contacts on 14 bridge the gap, allowing contact 
between 14 & 47 (47 is ground, or common, for all these 
contacts/functions.) In normal operation, on the car, the shaft can't 
rotate far enough for the double contacts to both cross the gap 
between 47 & 14.

It's also important to notice the spring contacts at the end of the 
wiper arm. One contact disables the alternating ("throttle pump" 
contacts if the throttle is closing; the other disables the idle 
contact if the throttle is opening.

>  If the injecotrs do not shut off on decell then wouldn't the 
> fuel still be injected and cause un burnt fuel to burn in the heat of the 
> exhaust.

Possibly, but keep in mind that you'll still be getting spark.

Some California cars in '72-3 came with a damper that slowed the 
closing of the throttle so that you'd keep injecting for a short time 
during overrun. Apparently, that produces less emissions than cutting 
off injection quickly.

>  I just find it odd that suddenly after tightening the TPS terminals the 
> popping out the exhaust no longer happens. All the other FI terminals needed 
> to be tightened yet were no where close to as loose as 14 and 17 .

I don't see how loose 14 or 17 would cause any problems, either.

A loose contact on any of the other 3 could mimic the "throttle 
valve" contacts, however, and might create extra injections.

Note also that the '73 TVSs have a tendency to develop tiny cross 
contact shorts between 20 and 9. Check this with an Ohmmeter: connect 
it between 20 and 9 and slowly open and close the throttle. If you 
see any twiches of the Ohmmeter needle, try cleaning the spaces 
between the little interdigitated gold 20 & 9 contacts. If you can't 
get rid of this, you'll need to replace the TVS, or disable those 
contacts by putting a bit of insulating plastic under the 2 
stationary spring contacts that connect the board to the connector.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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