The two times my  '85 didn't start were right after some wet weather.  It
cranked very slowly and would not start.  This is after starting all winter
with 20-50 oil (Delaware winters).  The starter is new (less than a year
old) as is the alternator.  I swapped in the  battery from my '89 Jetta
diesel (new Interstate this past winter) and it still didn't crank fast
enough to start.  I plugged in the 1-amp trickle charger and the weather
dried out some.   3 hours later,  it started and ran fine.   Is this a
ground problem?  All the stock connections are clean.  The battery ground
wire was good.   I want to upgrade the stock battery/starter wiring.  Would
running an extra ground wire from the battery to the starter help?   BTW,
both vehicles use the Group 41 size and it is a real pain getting at the
battery under the front passenger seat.  The lid is screwed down!  Is this
a camper thing?  My '86 GL had a flip up lid.

                                                        Jay