We had this drama a fair while ago in the 604 but i thought i better post in here for others who may have the same trouble
In 604's there is a coil relay ussually located under the coil/s and towards the firewall a little
can be easily replaced but when the relay fails the ignition lights will all come as per normal but the car will turn over and over without firing
an emergency procedure to get you home if you don't have a spare relay is to run a wire from the positive side of your battery to the positive side of your coil and start the car as per normal
the only thing is you can't turn it off untill you break this connection
when you get home replace the above mentioned relay
this hot wiring method is a good test to see if the relay is stuffed as you are bypassing by hot wiring
i'd advise not to drive too far without rectifying the relay as it is there for a reason and i don't want to see anymore burnt 604's
hope this helps a few 604 folks out there