clean and tighten ALL ground connections,
then try your known-good spare distributor.
( a set of known-good used parts like that makes all the diff in the
world in being able to track down intermittent stuff )

I had a similar situation in my own 85 ...
it would start loosing power after 2 hrs driving on the
Interstate...Like barely be able to limp off the freeway.
  A new Hall Sender in the distributor was the real fix in the end.

I also do things like inspect the ECU connections, for example. .treat
that area with Electric Contact Cleaner. ..
a majority of what I fix involves 'connections' .
much more than 'components'.

oh yeah..had the same thing on another 85 I own ( that I'd sell ) ..
was a running project car for months ...
one day, start...die in a minute or so.
restart...but not really run.
Spare distributor made that one happy again too.
Watch out for the wires and plastic gizmo they sit in, on the side of
the distributor.
those break easily ...the wires can get pulled on ...just a weak area.
But it's the electronics of the Hall Sender that I find to eventually
get intermittent and dodgy.
Ignitors ..almost never had a problem with one.
Same for coils ....though think about that too.

Scott

On 3/23/2016 11:14 AM, paul gordon wrote:
> I have been traveling down in Florida this winter and have had a problem that I thought I would throw out to the group and get some opinions.
> 1985 1.9 WB Standard Transmission. Traveling along at 60mpg and begin to slow down. Just as the clutch pedal is depressed to gear down the engine dies, all panel light illuminate  and it cannot be jump started. The only way to restart the engine is to stop the vehicle turn the ignition key off and start normally. Any thoughts? Paul.