Firing order for 1987 420 sel

I have A 1987 Mercedes 420sel and it won't start I'm not getting any spark to the plugs , I've changed the plugs and the distributor cap and the rotor and the wires, can the distribitor cap be installed incorrectly/ What about the firing order?
Thanks Steve

You can't really put the dist. cap on wrong. If you still need the firing order it's labeled on the valve cover, but if your not getting any spark to the plugs that's not your problem. Check to see if the trigger wire for your ignition is in good shape i.e., not shorting, plugged in, and has continuity. It's the wire between the distributor and the control unit(GREEN). Check for power to the control unit and the coil. Check dwell..Check your grounds..Good luck.