DME Found missing grd no start

[84 944 oneowner]

Hello to all again, ok after all tests that were done i have found the ground on the dme that closes the loop for grounding fuel pump that energizes the dme relay. In turn also controls ground loop for inj not grounding. So here is the question> Anypne know where to find on the dme board a lable diagram for it? I need a diagram of inside of dme computer to fix the board. Thank you for any help as well as all the help provided.

[RC924]

Sure, schematics are on Clarks Garage and using the search feature here will lead to pics, PCB layout and more info.

[84 944 oneowner]

ah thankyou so much when scoped from both speed and ref sen it for sure wasnt reading due to a belived faulty ground from dme i think thanks again so much

[John_AZ]

Just a suggestion before you try to rebuild the DME .

A few members have successfully resoldered the DME.

Early DME repair write-up with pics. - Rennlist Discussion Forums

OR

DME Repaired w/pics - Rennlist Discussion Forums

You are determined.

GL
John

[RC924]

Sounds like you know enough about electronics to at least tackle this. Kudos, most other guys would simply be chasing a second hand DME.

Obviously check all connections and for dry joints on connector and switching transistor which is as far back as I think you will need to chase it. If the transistor proves faulty there are more modern substitutes.

Here is the 951 schematic which is easier to read, output stage is similar.

Good luck.

[John_AZ]

Originally Posted by 84 944 oneowner

ah thankyou so much when scoped from both speed and ref sen it for sure wasnt reading due to a belived faulty ground from dme i think thanks again so much

If you have "scoped" the speed and ref sensors, you have gone beyond what many have the knowledge and equipment necessary.

So if I can offer another DME OEM worksheet with values.

The Porsche 944 Motronic DME

Also here is a flow chart of troubleshooting that may be helpful



GL
John

[84 944 oneowner]

Hey guys, wow i cant belive i have recived this much help and info, lol cant say it enuff thankyou. Yes i belive i have narrowed it down to pin 19-20 on dme -20 on the transistor. I am keeping all crossed, fingers toes, legs, and anything else i can find lol thanks again i will give it run again tonight. Will try and get some pics posted

[84 944 oneowner]

Hello again, just wondering if specs on dme testing are the same for 84 vs 85 1/2 thankyou

[John_AZ]

Short on time to give absolute answer, sorry.

FR Wilk may have the answer here or on his site.

DME (ECU)

GL
John