1985 944 - No Start Diagnosis Help

[MossRestoration]

Hi Brains Trust.

I'm hoping someone can help me troubleshoot a no start situation on an 85 944... I'll give you some back story so you know what I'm dealing with.

Sorry in advance, this will be long winded and I'm not the best writer.

A customer has purchased this car as a project and sent directly to me to have some rust repair work done as well as diagnose and potentially fix a no-start situation. He doesn't want the car restored, he just wants me to fix the couple of major issues that are beyond his ability so that he can then take it on as a passion project.

The car itself seems to have seen a dozen different owners who have all "had-a-go" at getting the car running.

So far, this is what I've fixed/replaced and why.

- First step was to fix the rust issues. It's a RHD with the battery in the scuttle tray directly above the fuse box/relay box, when it came to me, the battery tray had completely corroded away, meaning all the electrics underneath were soaking wet with plenty of corrosion on all the joints. relays full of water, and all the earthing points on the under side of the tray no longer doing their job. The battery tray is now re-fabricated and installed including all the earthing points.

Everything I've checked in the standard process for diagnosing a no-start had appeared to have been played with when I looked. Most had been played with... incorrectly.

First was the coil, wiring was back to front and an incorrect coil had been installed. I found an original one in the back seat of the car, tested this on the bench, (resistance and manually collapsing the field to generate a spark) Tested good so it was installed.

Second were the speed and reference sensors. Initially I wasnt getting a reading at all at the DME plug for either of them, so I went looking at the sensors themselves. the plugs on both the loom and the sensors had been replaced with spade terminals. Haggard but should still work. I tested for continuity between DME plug and DIY connectors - NONE and with no obvious place that I could see for a failure and the price of a new engine loom being reasonable, this was replaced. Along with both sensors. When removing the sensors there were shards of metal on the ends, so I checked the gap and sure enough this had been tampered with too. So the new sensors are now in with a correct 0.8mm gap on the speed sensor (closest to the back of the car).

The DME relay was full of water and since it needed replacing, the customer decided to get a solid state relay with the diagnosis LED's.

After all this, still no start.

-No fuel pump (pump itself is fine, looks new and replaced by one of the PO's) No power at the pump at any stage.

-Still No Spark

-No tach bounce on cranking.


Not that it matters at this point with no spark, but injectors are all showing 12v with key on.

LED's on the new relay currently all come on for a few seconds and then the CTR FUEL PUMP and FUEL PUMP Lights go out.


My thoughts at this stage is the next issue in the series seems likely to be in either the wiring loom between the 9 pin firewall plug and relays (car loom). The DME itself, or potentially both. It seems likely that with all the obvious work thats happened by previous owners, the car has been attempted to be started with the fuse box and relays all full of water.

Before I just go throw the customers money at a new DME, I'd like to bypass the cars loom,relays etc entirely just to be sure. (the wiring loom at the fuse box has been extensively tampered with. lots of soldered joins and splicing, relay cabling extended etc) I dont think it's not fixable. but at this stage, it would be significantly faster to bypass it all I think so that the DME can be tested and thus all the other components on the engine.

Does this sound like a reasonable plan? If I can get spark, then I can temporarily power the fuel pump to check other systems. No one has an endless budget and I'm doing my best to keep it as low as possible for the customer.

So with that in mind, does any one know which pins need power and which pins need ground and is the 9 pin plug the best place to intercept this? I'm assuming I will also need to run new wires directly to the coil since the engine loom isn't what connects to the coil.

[MossRestoration]

Okay, there is definitely some odd things going on with the wiring.

I have 12v at both pins of the injectors even with the DME Relay completely disconnected.
I also have 12v at both sides of the coil with the DME Relay completely disconnected.

Also, I forgot to mention earlier that this one doesnt look like it was ever equipped with an alarm.

[944 Ecology]

https://www.clarks-garage.com/shop-manual/ts-01.htm#fire

[Monkey Wrench]

maybe you could check fo r a pulse on the sensor wires, a scope or soemone here had a good idea, connect a radios input and listen for it. ( poor man's audio osciloscope)


you might connect up a few test lamps , ECU power maybe or fuel pump power, "power feed to dme relay?
maybe node lights between the injectors and their input cables. I think if you see in real time by using some temoorarily connected small bulbs, you can then tell when things are on or if power is missing. you cna check with a meter of course but then you go use the meter for somethign else. with small bulbs you can monitor 10 power locations in real time , low cost in that.

I know in my volvo if I pull the fuel rail to try to watch the injectors spray, the injectors wotn fire if I dont reconnec the ground to the engine. someone here might have a source for "noid lights" if you plug them in betweent he injectors and wires you can see them flash as the injectors fire. in real time.

youcan go connecting small bulbs to questionable relays and such to study them for intermittent issues etc. what that can do is just dumb things down a little so you can see visually where the power is or is not.

the battery negative lead is important and ground to engine, almost everything electrical relies on a good return path. You obviously know that if you are this far in, you obviously have good electrical troubleshooting skills.

Id lift and celan every single ground you can find or come across with the moisture especially thoise bad grounds can hide themselves, and poor grounds can cause intermittents and hard to troubleshoot issues.

Ill clean and I use "penetrox A" its a grey grease like substance, if it see it near a ground teminal, I know Ive already cleaned that ground connection , if not I clean and then apply it. If I see no greay stuff it still needs doing.

https://sds.chemtel.net/docs/Rexel%20Holdings%20USA-0004804/FCI%20USA%20Incorporated%20Burndy%20Electrical_Pen etrol-a%20Oxide%20Inhibiting%20Compound_Unknown_01-17-2002_English.pdf

you mientioned the engine sensors were attreacting metal, I guess being somewhat maggetic , they are coils essentially, could there be more debris in there?

in some 944's the clutch center is rubber and can dissintegrate evidently a sign is rubber debris in around the starter motors gear, maybe if you pulled the starter you could see in ther better? clean and inspect? it definitely won't start if you loose the timing pulse(s) the tach blip is a sign.



sounds liks a frustrating project, you may be up against several reasons for a no start due to people mucking about before you. Vey frustrating.. I hope you are successful. Just taking this on is admirable.

[MossRestoration]

Little update, I have confirmed that amongst everything else, the DME has failed.

Both sensors were working perfectly, with all required wires showing perfect continuity for the DME to get the info it needed to trigger the coil. The cars harness completely bypassed so running 12v to pin 18 & 35, as well as 12v to the + side of the coil and jumper from pin 1 at the DME directly to the negative side of the coil. As well as ground run directly from battery to all the pins that needed ground at the DME. thankfully the new loom (and a continuity test) confirmed they were all getting it from the 2 earth points on the engine, but I ran a jumper from the battery negative to those lugs just in case.

With all that still the DME wasnt triggering the coil, so as a final step to confirm, I wired in a Bosche ignition module between pin 1 and the negative of the coil to amplify any signal that might just be two weak to fire the coil and still nothing. Very confident the DME has failed.

Interestingly, the cars wiring is so messed up that the fuel pump now works via the key as you would expect it to when the DME/Engine loom is completely disconnected from the cars loom.

A new DME is going to be ordered, customer and I are thinking along the lines of an Ftech 9 brand new unit. Seams a reasonably price, anyone have any experience?

[Monkey Wrench]

this page has soem interesting . worth the read. it has some depth on the coil's charge cycle time and related info.

https://roguetuning.com/944951_ignition

It seems to mention the transistor on the DME, but I wondered if this part was also involved, and from there Im a bit grey.

Its been my understanding that this component , which I believe is mounted near the driver side fender area is involved? Im not clear if it was perhaps not part of the design of this particular DME. ,

https://www.design911.com/uploads/products/1cc3fee9-d7f9-4456-a315-04528922c2a9/92860270601_3.jpg

im not sure if that link might get blocked, in case itgets blocked here is anothe rpic of the frontside of the thing. just as a visual reference.

https://www.douglasvalley.co.uk/images/20000/19533/fancybox_IMG_9521.JPG

I figured it was sort of a little amplifier, transistor basically and sits beteween the DME and the coil electrically. others can explain better about the imporance of it or if or why it exists and how to check it,

I just thought if this component failed it might add confusion or perhas be the culprit

I know in a volvo it has one too and it has some heat putty to transfer heat to the body so obviously it needed that for extra cooling of the component itelf.

Ill leave off here because I think others may be a lot more knowledgeable on this from an electrical engineering standpoint.

I could be off but this comment seemed to suggest to me , the component was bypassed.

"The cars harness completely bypassed so running 12v to pin 18 & 35, as well as 12v to the + side of the coil and jumper from pin 1 at the DME directly to the negative side of the coil."

the link above was to a page within and the main page was https://roguetuning.com
it seems to also link from within to Lindseys racing. so their site might be somehow related

https://www.lindseyracing.com/LR/Parts/944MTUNE.html

[MossRestoration]

Hi Monkey Wrench.

That unit is a Bosche ignitor module and exactly the unit I wired in during my testing. It can indeed operate as an amplifier of sorts which is why I wired one in as the final step to confirm the DME had failed.

Although they are installed factory on the later 16v 944's. The earlier 8v motors did not have one. It can still be used (like I did) to absolutely confirm that no signal is coming out of the DME to trigger the coil.

[walfreyydo]

Ok so no power to the pump right away indicates to me, an issue with the DME relay, one of the components which trigger the relay, or the wiring to the pump/fuse itself. There are no other components that control powering the pump, so its got to be one of those things.

If you review the diagram of the relay (you have been reading and using Clarks to do your diagnosis I hope) youll see that in order to power the pump it needs power from battery (pin 30), ignition switch voltage (pin 86), DME ground (pin 85), ground from DME to pickup fuel pump (pin 85b) and then power to fuel pump (87b). You should check all those pins in the fuse panel for either ground or continuity/voltage. If any of those fails, you know where to start looking.

Start there and work through those pins until the pump comes on and you are getting fuel (and correct fuel pressure, yes with a gauge on the rail), then move over to diagnosing the no spark condition. George linked a very very useful page above to the Clarks Garage engine troubleshooting guide. I recommend reading through it, follow the no fuel and no spark diagnosis steps. If you have fuel pressure and you confirm spark, the next step is to look at whether injectors are getting 12V (wiring) and if so, a firing signal (noid light) - this is also outlined on Clarks.

[Monkey Wrench]

since you obviously have a good electrical background and seem to feel you need to buy a DME , how might you feel about just going to an electronics shop and buying comparable electrolytic capacitors and soldering them in?

what I did before ( on a ford bosche ECU) was clip the cans about 1/ 8" or so above the board. Watch you dont get squirted with the stuff. it might be PCB's or something real bad for your eyes.

on your new cans, wrap each lead around a pin so its like a spring , then slide them over the stubs and solder, the reason I did that was because I'm a little afraid of the tiny soldering. it also avoided needing to muck with the heat putty to work on the solder side of the baord.

the capacitors have a line on the can indicating negative, don't get them in backwards.

does the board also have a diode? maybe they woulld be easy to check or replace.

I dont know if it will help, but worth a go maybe? whats to loose? the ability to have it exchanged? maybe?

the caps are cheap and at around 35 years old , well they do tend to expire , fail leak their stuff..

try to look on the board just below them. Ive seen where they leak their electrolytic fluid causing a light stain just below the component ( capacitor) on the board.. Sometimes they bulge out at the ends, a physical sign of failure.

the caps are very cheap, the board isn not. its a bit of a crapshoot, sure.

I blew one up in a volvo once, there it is called an ECU, it did not like the fact I'd somethow got the polarity at the battery, or a charger wrong, the board made a POP sound, I had a spare I did not try to find out what had popped, likely just one component? for sure that F-UP blew my ECU.

the actual fiunctionality of the thing at board level, thats way beyond this guy but I'd change caps, maybe save some cash if you are lucky? likely the right guy could check things like transistors or diodes and indeeed resistors. the chips and or Eproms remain mysterious little things to me ..

electrostatic discharge (static shock) can blow the Eprom You can ground yourself with a wrist strap to prevent discharging a static shock. That can wipe them out.

thinking maybe someone before you made a little mistake , cables backwards or accidentally "shocked" the E-prom / microchip

those might put it in "won't start mode"

possibly looking at the actual components closely could show something burned.



how about listen to the others ( above) who are much more knowledgable and then as a last resort , after you have tried everything you know or wwere prompted to , just before you go spend a thousand or so, where there is not much else to loose, then try a "re-cap" ?

[MossRestoration]

Thanks for all the responses everyone.

I had already completely exhausted the Clarks Garage troubleshooting before coming here.

DME Relay has been completely bypassed along with the rest of the cars loom during the later tests.

Although I could have replaced all the basic components in the DME, it wouldn't have worked out financially well for the customer for me to do so. I managed to find a local company who have now reconditioned the DME. (multiple faults found amongst it, many cracked solder joints, and a few blown components) Back in the car and initially still with the bypass loom in place I finally, finally had spark. It didn't however sound like the injectors were firing, so moved onto that. Luckily just a quick removal and clean and some manual firing managed to clear them up enough to work on their own and now the car is running.

Impressively given how many things were wrong with the car and the near 20 years it's been in a non-running condition left to waste away, it actually is now running quite well. Next to no stumble, power steering, aircon, alternator all working. Auto shifting well. No vacuum or fuel leaks. Not even any smoke.

Anyway, its now back off to the customer for him to continue on the restoration journey. Was just with me to tackle the big hurdles like rust repair and getting it running.