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If everything else is OK, A bad or no refrence sensor signal to the DME will still give you spark; it's just at the wrong time. Bad or no engine speed sensor will prevent the fuel pump from running except when there is a start (engine cranking) signal present. I'm pretty sure you need the speed sensor signal to fire the fuel injectors and spark as well. The tach is also driven from the speed sensor.
In general, the speed sensor counts every tooth on the flywheel and tells the DME exactly how fast the engine is turning; the reference sensor pulses once per revolution when a small iron set screw in the flywheel passes. This tells the DME where it is in the combustion cycle (where is TDC)
It sound to me like you are not getting any power to the DME. This could be in the relay or due to the alarm.
Power comes in to the DME through the DME relay on pins 18 and 35 in the main connector, these are heavy red wires with a yellow stripe. Check to see if you have power there while cranking and ignition on. if not, then suspect the relay and/or the alarm.
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-John
'94 968 Iris Blue
'85.5 944 White - Rally Cross and wrenching practice
'84 944 Gemini Grey (gone, but missed...)
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