86 944 turbo no start

[zooklm1]

I went to start my 944 this evening. It started, ran for a couple seconds, roughly/stumbling at idle and then quit. I tried to restart it and it cranks, gets fuel, speed and ref sensors are good. I checked the basics and still no start. I am thinking about swapping the DME with a spare. Any recommendations or key items to test?
Thanks,
Lee

[Tom]

I went to start my 944 this evening. It started, ran for a couple seconds, roughly/stumbling at idle and then quit. I tried to restart it and it cranks, gets fuel, speed and ref sensors are good. I checked the basics and still no start. I am thinking about swapping the DME with a spare. Any recommendations or key items to test?
Thanks,
Lee

I can respond in the morning and hopefully help, but in the meantime try asking Carbot in its forum
below. 951 no-start is well covered in its 'curated' knowledge base...

[chrischrischris]

The DME computer is pretty robust, so unless it got wet recently I would suspect something else is the problem. Access to the DME is pretty easy, so no harm in swapping another unit. Did you do any work on your car recently? When was the last time it was running? Any evidence of gasoline leaking through the diaphram of the fuel regulator & damper? Can you hear the fuel pump running and does it sound normal?

[danmartinic]

The DME computer is pretty robust

I respectfully disagree, at least at this age.

I have had to re-solder mine twice in 7 years. The parts themselves seem to be very solid but those solder joints... with all the vibration (how many have fresh motor mounts lol) I'm surprised they don't crack more often

At this point, it's practically basic maintenance: change your timing belt and re-solder DME same time

Or buy the FTech9

[walfreyydo]

Are you lacking fuel or spark?

Usually the DME is sort of the last thing you replace once you have tested and verified everything else, since there is not a great way to test the DME (there are companies that you can send it out to for testing through), but they do go bad.

So depending on if you lack fuel or spark, Clarks will walk you through the diagnostic process starting with those two basic tests. Once you have exhausted those steps, then maybe its time to try swapping out the DME.
https://www.clarks-garage.com/shop-manual/ts-01.htm

[zooklm1]

Thanks everyone for the suggestions. I have looked at the normal things like DME relay, engine position sensors, etc. I have not checked spark thru removing a plug and cranking the engine(will do this afternoon). I am getting fuel to the injectors.
Lee

[spacecad3t]

Thanks everyone for the suggestions. I have looked at the normal things like DME relay, engine position sensors, etc. I have not checked spark thru removing a plug and cranking the engine(will do this afternoon). I am getting fuel to the injectors.
Lee

Maybe a long shot, but is it possible that the battery was weak and it got drained? Did you notice the volt gauge while it was running? I have seen an old alternator create drag on a cold engine and make it run rough, produce weak charge, etc. How old is the battery?

[danmartinic]

Are you lacking fuel or spark?

Usually the DME is sort of the last thing you replace once you have tested and verified everything else, since there is not a great way to test the DME (there are companies that you can send it out to for testing through), but they do go bad.

So depending on if you lack fuel or spark, Clarks will walk you through the diagnostic process starting with those two basic tests. Once you have exhausted those steps, then maybe its time to try swapping out the DME.
https://www.clarks-garage.com/shop-manual/ts-01.htm

To remove and re-solder inside is not particularly difficult, is relatively quick, and chances are very high solves DME/ECU issues

No need to send out for testing or pay big money for replacing

All you have to do is get a cheap soldering iron.. solder.. sponge or cleaning mesh.. & magnifying glass

Open it up.. put some solder on the tip of the hot iron.. and quickly touch any joints that have little lines on them. You can add a bit of solder but usually just reflowing seems to do it

IMG_9458_Original.jpeg (480.32 KiB) Viewed 376 times

IMG_4113.jpeg (1.79 MiB) Viewed 376 times

In the pic above you can see both bad joints (lines with arrows) and freshly touched up joints (shiney). Very easy to do!

With zero skill or knowledge I was able to perform this twice so far and each time the improvemnt in drivability--in addition to solving the problem--amazed me

I would put money down that doing this to every DME currently in service with at least 100k miles today would result in a marked improvement of some sort

FYI I also did this to my original Made-In-West-Germany DME Relay and it's still in my car today

[danmartinic]

At the very least as part of regular diagnostics remove the DME/ECU and if you see ANY little lines like those above, it is not functioning as it should be

[Tom]

Does the boost gauge go to 1 when you turn on the key? This is a good proxy for whether the DME is getting power.

Does the tach bounce or twitch when you crank the motor? This is a good proxy for speed and ref sensor (harness) health.

Why do you say the speed and ref sensors are good and that it has fuel?