Clean & secure all connections in the battery to starter circuit. Don't assume they're OK - remove, clean & tighten them all.
Remove the fuses, clean all the contacts with a brass brush then put in new fuses. The bullet fuses used in our cars are known to look OK but not pass electrons when they get old.
Read through the L-jetronic Diagnostic page (link is in my signature) for other things to check - like the flywheel sensors and the fuel pump fuse.
While you're doing the above, charge up the battery. L-jet (if that's what you have) requires at least 10.5V to power on the computers and send the make sparks/squirt fuel signals. It can sound like it is cranking over OK but if system voltage is below that threashold it won't start.