Carrera 3.2l NO Spark

[sleepdoc]

Hi all,

My 1986 3.2l Motronic / 914 conversion has hit a snag, and I need some direction.

The engine is completely installed, wired, instrumented, and ready to start.

I have never seen this engine run, but it was purported to run on engine stand by PO.

When I crank the engine there is no spark.
None, no output from the coil.
There is good oil pressure, and compression.

The notorius DME relay comes on with the ignition, and the fuel pump relay
comes on with cranking. There is 12V at the + coil terminal. The coil has nominal
resistance between termnals. The battery is new and charged.

I have gone through the Bently check out of the fuel injection sensors' wiring and
function as measured at the fuel injection dme connector.

I have observed the reference and speed sensor signals at the dme connector
with an oscilloscope.

I have worked this problem long enough now as to start to doubt the dme.
Unfortnatley I live in a porsche scarce enviornment and can't find a running carrera to test the dme on.

Does anybody have any diagnostic ideas? Anybody interested in me sending you the dme
to test on your car?

thanks Mark

[rstoll]

Is it possible to swap the speed and reference sensors on your engine. Bought my 944 as a basket case. On reassembly I had the two sensors swapped, no fire. Swapped the connectors and she fired right up.

------------------
Robert Stoll
83 SC
83 944

[sleepdoc]

Robert,

Good Thought, I have traced the sensors to the connectors, thence to the DME. I actually measured the sensor signals at the DME connector with an osciilloscope. I know the correct signals are arriving at the correct pins. The Bently book mentions this specifically also.

thanks Mark

[sleepdoc]

Gentlemen and ladies Please! I need some ideas.

thanks Mark

[Kurt B]

I'm posting only because you're out of ideas. I chipped my 3.2 but found it one of the early soldered in kind, so I had to unsolder the old one and solder the new one in. The first time I did this, I missed a pin, and the car got no spark. It would crank and stink like gas but would not fire at all, not even roughly.
After I checked the pins and resoldered, it started immediately.
The Bentley does have checked for the DME, and you don't need an break out box if you just want to peel the rubber off the wiring harness. I'd go through those and check the ones you can check with ignition on...
sorry can't help more.



------------------
Kurt B
1984 Carrera Cabriolet
911 Page
carrera_cabriolet@yahoo.com

[ez911]

Check your solder connections in the Motronic ECM,in particular the big three pronged diode thats mounted sideways.Had the same problem this winter,engine stopped dead.After much troubleshooting a guy on this bb said to check the diode ,and sure as hell,mine was never soldered and lost contact when I finally hit the right bump.Good luck,Ed.

[Eric Coffey]

You may want to see if a local shop/yard has a DME unit that they would lend out so you can just "swap and go". That way you won't have to open up your DME unit unless it is definitely the problem. Also, you mention that you are getting no output from the coil, but 12V at the terminals, so you checked the coil itself right? Keep us posted.

-Eric

[This message has been edited by freefly (edited 09-05-2001).]

[sleepdoc]

Thanks Eric

I have checked the coil against the nominal resistance values. I don't know how to check it under more dynamic conditions.

Unfortunately I live in such a rural enviornment that there are no shops with dmes to try, in fact I have contacted the state PCA secratary to see if he knows anyone with a 3.2l in this state.

[nhromyak]

Did you check the resistance levels on the Coil and on the BOSCH CD Unit (sheesh I forgot what this is called).

Check the four or five brown ground wires that should be connecting to the #1 cylinder intake. I noticed when these are not grounded or a poor ground, there is no spark.

Check all other grounds as well (transmission ground strap, etc.).

I beleive these hold the ground for the CDI unit, and the coil.

Good Luck


------------------
Nick Hromyak
'85 Carrera 7 & 9 Fuchs
Havin' Fun in Sacramento

[This message has been edited by nhromyak (edited 09-05-2001).]

[This message has been edited by nhromyak (edited 09-05-2001).]

[Ned, NYNA11]

Mark,
Airmail/fedex it to me and I will install it in my 87.
Ned Monaghan

[Joeaksa]

Mark,

Where do you live? I have an extra 3.2 DME computer so if you live close we could swap them to troubleshoot...

JoeA

[pete911]

I had the same problem on my car. I hooked a scope up to the coil on the plus side and saw the voltage go to zero while cranking the engine. My quick fix was to run a new wire from a switched fuse back to the coil. The engine now runs and starts fine. Make sure you have 12 volts on the plus side of your coil while cranking.

[jabb]

Sorry for stating the obvious...
Is the distributor rotating when the engine is cranking over ??

------------------

• Joe A.
• 84 911 Targa
• 75 914/6 3.0

[Peter Kelly]

Sure sounds like the DME to me.. if you talk real nice to the guy at Vertex he will probably let you buy one of their rebuild ones with option of returning it if it does not fix the problems (they did that for me)

[Early_S_Man]

One final check before you swap DME units:

Monitor both sides of the coil primary with a separate channel of the oscilloscope while cranking the engine. If you don't get ground pulses on the low side of the coil and a farly steady 11-12 Volts at the 'Hot' side of the coil, check the power for the hot side of the coil.

If you have good power at the hot side of the coil and nothing like good pulses at the Low side of the coil, check the coil output lead at the DME connector.

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[sleepdoc]

Thank you all very much for input.
I have opted to send the DME to Ned
to try in his car. I will post an update
When he has had a chance to try it out.

best Mark

[sleepdoc]

Hi All,
Well Ned checked out the DME and it is infact kabroken.
Does anyone have a circuit schematic for the

Bosche 0261 200 050
or other bosche m3.1 DME?

thanks Mark Robinson

[DRD]

I have a rebuilt DME for sale with a warranty from vertex,reciept and all the paper work.I never used it. Email if interesed.
DRD
Darren

[sleepdoc]

Followup
Thanks all for input. With a rebuilt DME she fired up instantly, runs well except for some
popping at cold idle. Now I can get on to working through the remaing small problems prior to running Ruby on the street.

Thanks again Mark