Might be the distributor, but the usual failure mode is permanent, requiring
a replacement unit.

Computer? Perhaps. The ECU is located in the RH A pillar area. If the cover
is removed, the board can be inspected for leaking capacitors, a relatively
common problem. One symptom is sudden engine failures. The ECU also controls
the MPI relay (see below). The problem might be simply fixed by removing and
replacing the three ECU connectors, using a squirt of WD40 on the contacts.

Since you were pursuaded to replace the fuel pump (e.g. because of an ECU
error code), I suspect the problem is in fact the MPI relay. This is the
relay you (should) hear clicking from the RH A pillar area when you start
the engine. This relay controls power to the fuel pump, and are also a not
uncommon problem. You can source a used relay from a 93-96 Summit wagon /
Mitsu Expo.

It MIGHT also be the IGN switch. After a while the internal contacts get
worn and don't always make good connections. My 93 AWD wagon has this
problem with the START position.