no spark... from DME failure???

[MrPants]

my car has been having a no start issue. ive been sick these past few days so i had the car towed to a nearby mechanic. they say it has no fuel AND no spark. they think its DME failure.
my question is, does the DME even regulate spark at all? if the DME is bad i should stille have plenty of spark, correct?

[SoCal Driver]

The DME relay first provides current to the DME and the injectors. When you crank the car the second set of contacts close powering the fuel pump.

So IF the DME relay is not working, first powering the DME, then there is no way you will have spark (reference sensor) and no way you will have fuel pressure (pump).

Unless you ask the mech certain direct questions (threatening his prowess) you can't trust his determinations that it's the DME.

Here are the questions:

With the key on did you find voltage at the coil and at the injectors?

If no voltage at the coil then the ingition switch is bad. Common.

If voltage at the coil but not the injectors then the DME relay is bad or there is a break in the wiring to the injectors.

If there is voltage at both then ask:

Was there spark at a plug?

If there is no spark at a plug ask:

Was there spark at the coil?

If there is spark at the coil then suspect the coil to dist cap wire or the rotor being loose or even burned through. If the rotor does not rotate then suspect the timing belt.

If the wires and rotor check out OK then ask:

Did you test the speed and reference sensors?

Testing is to check that they have 1.5k to 2k ohms resistance and that the sheild is not shorted out to the sensor wires. There should be a plus 2 volt pulse coming off of the sensors when the engine is cranked over. With older cars the sensors plastic housings have cracked and will break the thing wires inside so you can wiggle them and the car may start.

If you have had the clutch or engine out recently you may want to check the clearence between the rear sensor and the starter teeth. 0.8 mm or about the thickness of a dime.

As to fuel delivery ask:

Did you jump between fuse #2 and #3 on the AUX fuse panel and run the pump?

Did the fuel pump run when you were cranking the car?

Only after the above is determined can you even come close to suspecting the DME unit.