Near end of a 10 mile drive while fully warm, engine simply shut down - all lights on dash lit up. Starter cranks and engine won't start. Do not have a code reader, and have not checked for spark, which I do not suspect is the issue. Car running excellently before. Only recent changes were 150 miles ago adding Boost fuel additive for first time, and an independent mechanic pulling out and putting back in the relays behind fuse box to be sure the A/C auxiliary fan was working, which it was. Wondering about CPS or possibility of the fuel additive freeing up possible sediment in tank, thereby possibly affecting fuel pump. Any ideas appreciated. Also, any suggestion on how to get a reasonably priced code reader for this model (OBD-1 ?) appreciated.