car has no spark.. help??

[Rico2301]

ive changed both crank sensors, cap n rotor, spark plugs, wires, and coil and still no spark??

[rick13]

You will find many similar posts as reference. Use the search forum function.

Rick

[quinnfiske]

I had that problem and did the same thing. Turned out to be the DME. The coil driver failed. I was told it happens all the time.

Don't forget to check the DME relay before you spend a bunch of money. Another common failure.

[buzzbom]

recently my car stopped running while i was driving home one night. I have another n/a 944 at home as well so i swapped dme relays. swapped coil. nothing . im not getting any spark to coil. no tach bounce. the connections of the referance sensors have been jerry rigged together by the guy i bought the car from and so i checked the ohms from the pin25 and 26 on the harness and pin8 and 6. the ohms read fine at 993. so im guessing the referance sensors are fine. i pulled my dme out from the floor board and opened it up to check solder joints they all looked dull couldnt really see any broken though. not sure what else to do. i would like to know exactly whats wrong so im not just buying useless new parts.

[mcarter]

When mine doesn't start I have to wiggle the ref sensor main harness. I have a new LR ref sensor harness to install someday.

[buzzbom]

well took my dme down to office max and had one of the techies look at the circut board looks like water damage some corrosian and some bubbly stuff. he says.... so i guess i need to look for a new dme??

[kdjones2000]

Send your DME to a place to have it tested. 944 Online will do it for free.

[buzzbom]

is there any way to check if the dme computer is bad while it is in the car??? multimeter??? i asked to bring the computer to a couple porsche techs but they told me they need the vehicle to check everything.. i would like to diagnose myself

[Arizona_928]

tach bounce?

[Along4ride]

First,

Check that the Coil has battery voltage on one of the terminals in the KOEO position. No Battery voltage = no spark and not the DME's fault.


Second,

The DME grounds the ignition coil using a power transistor. You can test if it is doing its job by disconnecting the DME wire from the coil and connecting a 12V bulb to it and the positive battery terminal. If it is good the bulb will pulse as the engine is cranking. An LED would work better, but use a 1K ohm resistor in series or it will blow out. The only flaw to this approach is that a bulb/LED does not draw nearly as much current as the coil. This test is only conclusive if the bulb does not light up at all indicating the DME is not grounding the terminal at all.