Does the starter switch on the grip need a certain amount of juice to activate? Mine tends to work more with a stronger charge and some times if I press it a certain way.

Does this indicate it's failing or can I fix it ?

I have a messed up shoulder so I would prefer to be elec start to be reliable.

 

1991 xplorer 400 4x4

 

First off check that battery,solenoid and starter connections are tight. Loose/corroded connections can cause problems.Plus at an idle the battery should be receiving around 14 volts from the regulator. If it's charging ok,but still has a problem,have the battery load tested. If it's ok,then could be corrosion in the left control switch.Use some electrical contact cleaner through the switch openings,press the starter switch,on/off slide switch,light switch back and forth.Left switch contacts over the years can corrode. Plus not a bad idea to check the control switch connection at the terminal board. Plus are you sure about year model? 400 didn't come out until 94. Explorer 400 came out in 1995.