'88 740 GLE non-turbo was having no ingnition response, just heavy single click. Following items checked and replaced:

1. Charged battery, only a couple years old
2. cleaned battery posts, replace one cable connector at positive side of battery
3. checked, cleaned and reset negative battery cable grounds to engine block and frame
4. turned engine over at crank shaft hub bolt
5. replaced positive battery cable after I was able to crank jumping the cable from the battery to starter
6. replaced starter/solenoid after having it checked under load
7. Pulled cleaned and increased connection tension on neutral safety switch which was replaced 4 years ago; switch contacts cleaned and looked good


After all this I was able to get the engine to crank when the automatic transmission was set in neutral position. But won't fire.

1. Sprayed starter fluid directly into throttle housing, NO fire
2. Check spark on #1 cylinder, NO spark

A complete tune-up was done 30,000 miles ago, including distributor, rotor, wires and plugs; plugs replaced less than 10,000 miles ago, too.

Car ran fine this winter, then all of a sudden wouldn't respond and started the heavy single click I started this description with. What is the next thing to start checking?