Check the fuel pump relay first. Those cars were famous for the relay to heat up and fail. That car does not have OBDII I had a 89 740 which had a simple computer system. A repair manual likely will tell you how to read codes. Or check YouTube. From there check for spark and fuel pressure it is like...

It also could be a broken timing belt. If it is broken, which you can determine by removing the front half of the timing belt cover, the valves will NOT be damaged. You just have to realign the timing marks and put the new belt on. A manual is very helpful but you can probably find a video online to...

I can't remember if the radio had to come out. Mine had a double radio Premium sound option. So likely the lower equalizer unit was removed. I traded it back in 1995 for a 850. Being a relay, put your hand on it and turn the key on and it should click when the power hits it. I do recall the tabs tha...