It could be a relay located under the hood with the misleading name of "radio interference suppression relay" which actually powers the injectors, among other things. I had an 89 on which it went bad. The problem was intermittent. The symptoms were that it would stall without warning while driving. It would restart as soon as you could pull off the road and come to a stop. It would then run normally until the next time it did it, which could be three minutes--or three months--later. Or, it can fail completely, as it did more recently on my 88. This causes it not to start.

This relay is (usually) clipped to the coolant bottle, just in front of the right strut top. It is black, rectangular, and has a four-pin connector.

The wiring harness is a possibility too. I had an 86, which I parted out, with this problem. It's pretty obvious---the wires will either be bare already, or the insulation will look dry and brittle, and will crumble at the slightest touch. It affects most of the wiring under the hood---look at the wires to the injectors, the alternator, anything else on the engine, and there is usually a large connector on the right side of the firewall that is easy to spot. Sometimes the wires to the front lights can go bad too.