Mark,

 My 87 syncro did it too.  I did a continuity(ohm) check on the (3) wires that
run from the "brain" under the rear seat left side to the hall sender of the
distributor. I used a FLUKE brand meter on diode checker to find the correct
contact on the parallel plug, the i used the Ohm setting. One of the (3) wires
read 5 ohms for a wire that is only about 6 feet this value was to high.  The
other (2) wires read a .2 to a .5 ohm reading.
Remember to disconnect the Brain after the key is OFF to prevent damage to it.
Keep in mind that the TACH runs off of the dist.

Did you hear relays and the injectors firing? mine did.

If you need more info please contact me!!!

kurt thomas
87 syncro
91 honda CBR1000 (m/c)
98 caravan (could not wait for VW to import a van-again)