As mentioned, the coil, rotor, or ignition unit (or their wiring) can cause a total lack of spark. You can check easily by putting a timing light on a plug wire and see if it flashes while cranking.

Can you check if the fuel pump is running while cranking? Put your hand on it while someone cranks and see if it vibrates.

Generally the the iginition units either work or die completely.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe