cool. when you have the no start condition check the sensor signal at the dme plug, which will verify or rule out the harness cause thats what its looking like.
lindsay racing has a nice section on the dme plug sensor upgrade

Thinking about it, I am not sure if my rev counter does bounce when I try to start her up..

I tried a new ignition switch, no joy..

I've got a new fix action (I don't play with the speed sensor plug anymore).

If I spray the relay/fuse panel under the dash with zero freeze when I have the no start condition (no tach bounce), the tach will bounce and it'll start.

I think I have a dodgy connection around this area. Getting close to finding the fault....finally!

Cheers,
Jeff

My Son's car 83 944 always have that kind off problem sometime it could go weeks, with no problem starting. I have tried almost everything there is to check. speed sensor /ref. sensor cap rotor coil vacuum lines, even getting the DME rebuild. First I tough I got it fix, by replacing the speed sensor & ref. sensor connector from Radio Shack. The original connector crumble from age. It turn out to be the connector on top off the booster brake, there is two connector 2 & 9 wire connector. On the 9 wire connector I found the wire (red/yellow) has been soldier together and the housing is melted a little (burn mark on the plastic casing. It just started again last week the car will not start (maybe it knows I wanted to sell it). Since my Son have upgrade his Car to a 87 944S. But then again since He live at home, I most likely have to deal with all the repair on His car, beside my own 944's . Anyway take a good look at the connector (2/9 wire).
Good Luck

-----------------------------
Bud

87 930 black
86 951 black
87 944S white
86 944 N/A Guards Red totaled
83 944 N/A white Auto
83 944 N/A black

Thanks Bud,

I know the connectors your talking about. I've given them a clean.

Cheers,
Jeff

Don't know if it's the root of my problem, but it certainly can't be helping.

I discovered today that my ingnition switch is intermittent.

Time for another parts order....

Finally got around to replacing the sensor harness with one from Lindsay Racing.

Now we, hurry up and wait!

Crap! Well, the harness is not the fault. The DME is next on the list. Bugger!

Well, I couldn't yet convince myself that it's the DME. Although, I came close to getting a refurbished one. The Aussie ones are not as common as the US or UK ones, although they would probably still work. But, they made Aussie DME's for a reason, don't know what that reason is...... Anyway, I not yet comfortable with the idea of parting with another $500. So today, I clanged the speed sensor, I got the Beamer 6 series one so often discussed (at half the price).

It worked a treat. The car started up no worries. Now we play the waiting game again......

My 83 used to do exactly the same thing. I used multiple nylon Ty-Raps to cinch up the sensor connectors very tight at the bracket until I replaced them with new connectors, AMP also. The Ty-Raps worked perfectly for 6 months though.

Clear silicon has been insulating those connectors for 12-13 years on my end. The bracket is no longer used.

I've been having an intermittent start issue with my 1987 924s for the past 2 years. I've replaced the DME relay, ignition coil, and DME computer, but the car still would only start when it wants to. Over the past month, I've noticed that whenever the car didn't want to start, it would always "pop start" with the clutch(this is why I've been parking it on inclines lately). I just now remembered a similar issue I had years ago with a Buick I had owned at the time. Even though it's starter whirled over fairly rapid, it was dragging just enough to deprive the ECM of vital current to ensure proper spark/fuel while starting. Despite turning over vigorously, I have noticed my Porsche starter lacks that new starter "zip", and has a characteristically deep, aged sound to it. I'm almost certain this is the cause of my issue! ;)

Yeah, my starter was also a little sluggish before I cleaned all my power and ground connections. My battery was only getting 12.9V from my alternator ATT. After all the cleaning, I now get 14.2V from my alternator and starting is strong.

The starter is scheduled for a overhaul anyway, the idiot PO has cross threaded the terminals on the starter. While they are being replaced I'll have the whole thing rebuilt.

So far she's been starting every time since the sensor change. Keeping my fingers crossed.

Cheers

Outback, is your car still having the problem after replacing the sensors? I have this exact problem and want to make sure that this fixed your problem before investing in a new pair.

Hi Razor,

The sensor only went in a couple of days ago (Sunday afternoon). It's too early to tell. My fault can disappear for a week, then return every day.

I replaced mine with the BMW 635i sensor (Bosch). The only difference is the tail on the sensor is longer. It's half the price of the genuine Bosch sensor.

Cheers

I noticed my car wont charge at an idle, I've replaced the rectifier in the alternator, but it still has this issue. Exactly what power and ground connections did you clean on your car? I've cleaned my battery terminals.

Clean;

Battery terminals and posts
Alternator terminals and posts
Starter motor terminals and posts
Chassis Grounds (engine bay and dash)
Engine grounds (bell housing)
Fuse terminals

I also cleaned the 9pin and 2pin connectors on the firewall, and the connectors/terminals for the AFM, TPS, AAV & both temp sensors.

The OPS also got a clean up while I was fault finding my OPG and the injectors connectors recently got a clean up when then new injectors went in yesterday.

Cheers

Five days now and all is well.

Giving it the ultimate test.......my 17 year old son has taken the car to school today.

I'm trying to bring my son's 84 944 back to life and have the same no start problems. The car has sat for 2 years, but when last run, had the intermittent no start that seemed to be related to the sensor connections. Thinking about the discussion on grounds, I remember that the radio would loose it's memory after about 10 minutes of sitting. I always suspected that it happened because of a bad ground somewhere, and now I'm wondering if that might be contributing to the no start problem.

Dave

Hi Dave,

It's possible that the grounds are an issue. It's worth cleaning them anyway. A lot of other things work better when you do (like your instruments tell the truth).

Cleaning the grounds didn't help my intermittent start problem but I'm glad I did it anyway.

I'm also glad I replaced the sensor harness with the Lindsay Racing harness. The original harness was hard and brittle and I kept breaking wires when manipulating it. The Lindsay harness is definitely a quality product and worth the $125.

And my boy didn't manage to break anything when he took the car to school yesterday. It's probably too early to call it yet, but I'm looking up.

Cheers