[tspin]

drove my car this morning then tried to start it a few hours later. turns over fine but will not fire at all.

 

then noticed this wire plus connector hanging down. see photo

 

is this the problem ?

 

thanks

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[Waylander]

Do you have a third party alarm system?

That is not a plug that I have seen before

Do you have a spare DME Relay if so change it

There can be a 100 reasons why a car won’t start

Can you see the other half of that connector?


If you are going to attempt to figure out why you have to start with the basics


Fuel flow

Sparks

Air


Are these basics in attendance?


The DME is always a place to start as the just fail without warning

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[ds968]

+ 1. DME relay is the biggest suspect . They do go bad without warning - best to always carry a spare, but until then, see if anything happens if you remove it and put it back and try to start the car. They’re typically seated very well, so doubtful it got a bit loose during driving, but can’t hurt to do that ..miracles occasionally happen .

Also possible a vacuum hose could have popped out of place, check the engine bay to make sure all hoses are connected and tightly in place .

P.s. No idea what that plug in the photo is.

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[MCL968]

Does the tach needle jump as the engine is turning? If not, you may have a bad crank/cam sensor.

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[pdxmike]

FYI you can make a jumper while you wait for a  new DME relay. I have actually made one out of two paperclips for testing purposes. 

 

http://www.clarks-garage.com/shop-manual/fuel-05.htm

 

That connector looks like a bulb holder to me - just has ground and one other lead going to it  - doubt it has anything to do with your no start issue. 

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[ds968]

FYI you can make a jumper while you wait for a  new DME relay. I have actually made one out of two paperclips for testing purposes. 

lol ... pdxMacGyver ! ( those who are not old enough to get this reference .. your loss )

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[tspin]

I put in my spare, new DME relay but still does not fire at all and no, the tach needle does not budge.

 

It is now at the local, independent Porsche mechanic's shop so will find out soon and I will report back.

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[ds968]

Ugh, bummer . Hoping it’s someting inexpensive.

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[Waylander]

that will be the crankshaft sensor then

 

probably the connection

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[MCL968]

Blink test?

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[tspin]

In the shop waiting for the senior mechanic to come back from hols next week.  So far confirmed getting fuel but no spark.  Installed a new coil but still no spark.  On duty mechanic suspects a faulty ground somewhere or, worst case scenario, a bad DME.  

 

Is there anyone that repairs or rebuilds the DME?

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[94SilverCab]

that will be the crankshaft sensor then

 

probably the connection

 

I would never bet against Waylander...just sayin'

 

Jay

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[J.Elenbaas]

Just buy a new one, they are not that expencive.

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[Waylander]

If you have no tach bounce on cranking it will be the crank sensor not sending a signal to the DME computer


They fail with age and heat, and a real pain to change, changing the coil was a waste of time it could be checked with a multimeter in seconds


The engine needs to reach 200 RPM with the pulse from the crank sensor to switch the fuel pump to run mode


Sounds like you have taken your car to a place that is not familiar with these cars and just swap parts till it runs, when installing the new crank sensor use a dime or washer that is 1mm thick to set the air gap because if they get it wrong the flywheel will mince the new sensor

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[BOB968]

I just noticed you are from Ottawa. My buddy with a 944 has had it serviced for years. at 


Metric Auto Service
912 Clyde Ave, Ottawa, ON K1Z 5A5
 
 
   
613-725-6052

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[pdxmike]

Waylanders suggestion is dead on - DME itself rarely just fails, and would be unlikely to cause a random no start. If the tach needle isnt bouncing it is very likely to be related to the crankshaft sensor or connection.


Doing a blink test may show a code related to the crank sensor. A Durametric would also help.

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[tspin]

968 back on the road today.  Apparently the coil went bad and damaged both the Hall sensor and the DME.  The DME was sent to Vertex in Miami for a rebuild and was in such bad shape that I was charged an extra $150.  Got it back yesterday (Vertex did a great job with a quick turn-around)  and it was installed this morning.  All good now. 

 

Was a spendy adventure with new coil, Hall sensor and DME rebuild plus labor but on the plus side was my only major unplanned for maintenance in the last 5 years.

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[ds968]

Thats good news , but the ignition coil can damage a DME ?! As in the main DME / computer itself, and not the relay ? Thats seems improbable if not impossible . I could be wrong , maybe someone knowledgeable in this area can chime in and correct me , but if thats true,its pretty disturbing to learn.

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[pdxmike]

Also glad you got it back and are on the road again.


I share Dans puzzlement. The coil sends high voltage charge to the distributor, distributor sends charge to the spark plugs, ignition of fuel/air mixture, end of story. No interface with DME whatsoever.


Porsche made some questionable design decisions with the 968; sending 10,000 volts into the DME wasnt one of them.


Much more plausible that a bad voltage regulator could fry the DME - Im not sure if a faulty Hall sender could do it. Would defer to Waylander on that...

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[Waylander]

I can only go by whats being said, but just faulty coil would not damage the ECU unless it was a dead short to ground even then its only a pulse signal generated by the crank sensor,


The hall sensor could have been busted for a very long while as the engine will still run without it, and I dont think anything could make it go pop as it again does not have any voltage running through it, it generates a tiny volt pulse of its own

Dme computers do go wrong but not often,


So Im a bit puzzled to

The only possibility is that a wrong connection has been made somewhere and pushed a full 12v back through the ECU

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