Rotten wiring insulation is probably your issue. On my 83 240 with B23F engine (non-turbo), the five wires that come out of a grey plug near the center of the firewall are usually the problem. You can cut them of two inches below the plug and run new 14 gauge stranded copper wires with oil and heat resistant insulation. Solder the new wires onto the 2" stubs left at the plug and cover the joint with heat shrink tubing. Route the new wires around the inner fenders to their final destinations. Leave the old wires alone; don't try to remove them from the main harness. Here's where the five wires on an 83 go (an 85 could be differnet): black (lower right corner of plug) to oil pressure sender; yellow (above black wire on plug) to temp sensor for gauge (not for fuel injection); red (above yellow) to alternator; yellow/blue (lower left wire on plug) to starter solenoid; fat brown (upper left corner of plug) to coil terminal 15. It helps access if you remove the intake manifold but it's not imperative. Use appropriate type and size of crimp-on connectors on the wire ends that connect to the devices. jp