It will turn over but will not fire.We have developed a no start diagnostic chart for just this situation.No Start DiagnosticsRelated Questions1990 mercedes 500slwhen at idle a\/c blows cold air ,when driving no cold air.1990 Mercedes 300ELoud squeal at cold start up in the morning getting worse. RESPONSE The most common cause for this would be from the Serpentine Belt. The belt is worn, loose or been exposed to anti-freeze. If the belt is worn, replace it. If the belts are…1989 mercedesthe odometer and heater dont work, why?