my 968 failed to proceed - starter motor

[Buchanan Automotive]

The 968  ( 1992 - 1995 ) has two completely different starter -motors 

Manual Trans Only  = 944 604 104 00   1.7KW  , this is an unusual design where the drive shaft (  Bendix shaft with toothed gear) protrudes out a long way with NO end support at all from the starter-motor itself  , the very critical shaft support is from a dedicated bronze bush pressed into the special 968 manual trans ONLY  alloy two piece bell housing ( the Tip version has a different bell housing ) .          This 968 manual trans starter- motor shaft "Support" bronze bush will quite naturally wear / chop out ,  and this worn bronze bush puts more ( sideways ) push / influence onto the starter motor internals & does it no favors at all ( extra internal wear ) , so with every clutch replacement or every 968 starter -motor replacement we always install a new bronze support bush in the bell housing & yes its a Porsche spare part ( 999 531 017 00 )  ( Manual Trans 968 only )

Note =  All  starter-motors wear out and / or become electrically unreliable in old age & yes the solenoid ( which is part of the S/motor ) can & do stop working , but they also suffer from the Armature ( heat soak / old age ) intermittent failures 

Note 2 }  Common starter motor ( Old Age ) failure mode  }  Engine & starter motor etc hot , meaning that car has been driven for more than 15 minutes & you stop the engine for 10 minutes and all you get is just a single click sound , then when it cools down ( it may ) operate again apparently normally until its gets the heat soak conditions & the failure mode repeats its self again

Note 3 } never ever seen where engine oil weeping , leaking onto a 944 / 951 / 944S / 944S2  / 968 has caused any real issues , its mainly just old age & heat soak electrical damage and wear , like we all see on all cars , be it  GM  , Fords , Toyota's , Mazda's , BMW's  etc etc 

Note 4 }  Earth Straps , engine to body & battery to body are critical + good quality calcium battery or similar

968 Tip ( Auto Trans )  , completely different starter motor , its still a 1.7KW but because there is NO dual mass flywheel , the starter motor looks similar to the one fitted as standard to the 944S2 , but its not , the 944S2 received the low output 1.4 KW & the solenoid design is different as well 

Note 5 }   968  12V  engine wiring harness ( the one to & from the Alternator , Starter Motor  etc  )  we had a high mileage 1993 968 in here recently doing a cam belt / rollers etc & when removing the starter motor ( to lock the crank ) we noticed deterioration ( heat soak / crumbling )  of the wiring loom insulation of the individual cables withing the 12V  harness , this was at first noticeable where the individual cables / wires were exiting from within the harness near the starter motor had noticeable crumbling insulation which when one thinks about it had quite serious consequences , for example the two most prominent individual cables / wires within this main harness  were the Terminal 50 wire & right up against it inside the harness was the main Non Fused main battery cable ( to & from the alternator & feed 12V into the cabin etc ) , and their individual plastic insulation/s were crumbling away quite badly , now if the terminal 50 wire touched the main battery cable ( both with crumbling insulation and against each other ) then the starter motor would engage and you would not be able to stop it ( think of the consequences of that ) with the car parked or engine running / driving ( Yikes )

So I opened up the old harness & its was bad every where we opened it up , so we stopped everything & fabricated an entire new 12V engine harness for this 968

Naturally we are now looking at all 968 models very carefully in this one area , but remember this particular 968 has done lots of city driving over the last 24 years & probably thousands & thousands of hours of heat soaking traffic conditions imaginable in its 260,000 Kms ( this is bad for wiring in engine bays )  , so this is the worst one we have seen , but we were lucky to catch this one before it became a real issue

We routinely make new 12v engine bay wiring harnesses for 951 & 944S2 Porsche's , and for the same reason , old crumbling wiring etc , but the 968 was different in so far as the extreme proximity of terminal 50 wire ( crumbling ) to the 12V battery cabling ( crumbling ) within its overall harness , it had greater potential to cause uncontrolled engagement of the starter-motor  

Regards
Bruce Buchanan 
Buchanan Automotive   41 years working on Porsche cars 6 days a week

[jakroo]

Do all the obvious simple stuff first and if that ain't it call in the experts!

Will do.  944s2cab has very generously offered his help and is currently on his way to assist the investigation.

 

Thanks Bruce, this a great deal of info that we'll take all this in to consideration.  Mine's a tipper.

[jakroo]

My new BFF Steve turned up in his white 944 Cabrio with a boot full of tools including a trolley jack and miscellaneous pieces of wire, swager etc ready to make good my broken down 968.  (try carrying that lot in one of those fancy air cooled cars :-) )

Some testing of volts at various points in the car all showed everything was okay but perhaps a little low.  A good peek under the car and the issue showed itself - a loose connection to the starter motor secondary circuit (note another technical term learned in recent days).  Something to get looked at by a mechanic.

A couple of spanners, some cleaning fluid and some electrical cleaner and protector stuff and we're all good to go again.

After a few short hours including the obligatory sit down to chat about our cars, and my saviour headed off home on his white stallion.

Thanks 944s2cab.  This is what makes this forum such a great place.  Sure, he could have spent time in his garage mucking about, or painting or fixing something of his own that was busted, but no, he came to help me out.

Thanks to everyone who contributed to the thread, much appreciated...and a big thanks to Steve for making the trip.....

 

[LeeM]

 Onya Steve ?

[Allan C]

I had the same with my 968 as Bruce pointed out in Note 5 and have since had insulation breaking down with other electrical components in the engine bay. As the auto electrician who fixed mine said, Europe do not see engine bay temperatures as we do on a hot summers day. He also said most European cars have this when the cars are getting older. He has fixed Mercedes with this failure which are 4 years old.

Thanks again Bruce for another extremely informative article.

[944s2cab]

My new BFF Steve turned up in his white 944 Cabrio with a boot full of tools including a trolley jack and miscellaneous pieces of wire, swager etc ready to make good my broken down 968.  (try carrying that lot in one of those fancy air cooled cars :-) )

Some testing of volts at various points in the car all showed everything was okay but perhaps a little low.  A good peek under the car and the issue showed itself - a loose connection to the starter motor secondary circuit (note another technical term learned in recent days).  Something to get looked at by a mechanic.

A couple of spanners, some cleaning fluid and some electrical cleaner and protector stuff and we're all good to go again.

After a few short hours including the obligatory sit down to chat about our cars, and my saviour headed off home on his white stallion.

Thanks 944s2cab.  This is what makes this forum such a great place.  Sure, he could have spent time in his garage mucking about, or painting or fixing something of his own that was busted, but no, he came to help me out.

Thanks to everyone who contributed to the thread, much appreciated...and a big thanks to Steve for making the trip.....

 

Thanks for the kind words, it really was no hassle at all, in fact a bloody good day, going for a drive and fixing Porsches plus meeting new people, 

Got to say, that is one hell of a nice car you've got, a bloody bargain if you ask me,

We'll have to arrange a blast around a track in the new year

[Dreamr]

Got to say, that is one hell of a nice car you've got, a bloody bargain if you ask me,

I don't want to put labels on myself or anything, but I'll take credit for that ..... 

[jakroo]

12 hours ago, Dreamr said:

I don't want to put labels on myself or anything, but I'll take credit for that ..... 

Indeed you should do Dreamr.  The previous owner actually rebuilt the car (as such) but you put them in contact with me so I could benefit greatly from their spending.  It is a great looking car that is now again 'able to proceed' after 944s2cab's ministrations.

[Jason E]

On 11/18/2017 at 5:19 PM, Allan 968 said:

I had the same with my 968 as Bruce pointed out in Note 5 and have since had insulation breaking down with other electrical components in the engine bay. As the auto electrician who fixed mine said, Europe do not see engine bay temperatures as we do on a hot summers day. He also said most European cars have this when the cars are getting older. He has fixed Mercedes with this failure which are 4 years old.

Thanks again Bruce for another extremely informative article.

Hi Allan,

can I please ask which auto electrician you use in Brisbane?  I am thinking of having some extraneous wiring removed, some rewiring & some preventative wiring maintenance performed & i'd like to go to someone who knows what they are doing.

cheers,

Jason

13 hours ago, jakroo said:

Indeed you should do Dreamr.  The previous owner actually rebuilt the car (as such) but you put them in contact with me so I could benefit greatly from their spending.  It is a great looking car that is now again 'able to proceed' after 944s2cab's ministrations.

I've driven this car & it absolutely was a cracker..........

[Allan C]

Hi Jason,

I used Kedron Auto Electrics - 35 Kate Street, Kedron. Ph 3359 4411. Steve has owned this business for over 40 years. I understand this is probably close to where you are.

Cheers Allan

[Ross B]

Guys,

I have had the same wiring failure mention by Bruce (note 5) and Allan 968, the Battery/Altinator/Starter harness. The problem was picked up by Steve at T&D Auto in Brisbane during some routine work. He mentioned he has replaced this wiring on a number of 968s, so any other 968 owners should seriously inspect this harness. As Bruce said the insulation breaks down with time/heat and can cause catastropic results. As the wires in this harness run in a sleeve the insulation breakdown on the wires inside the sleeve is often not obvious until the sleeve is removed. 

From memory to have a new harness made and fitted by T&D was around $450. My 968 engine has only 45K on it, so this insulation breakdown may be a function of time rather than just long term heat exposure.

Ross 

[Cam Arnott]

Good to know this potential fault gents. I might get the CS checked over shortly!

[Cam Arnott]

As it turns out I had the hot start issue happen to me on the Great Ocean Rd when I was on the way back to Adelaide after picking the car up. Pulled up for a leak and when I went to start up again all, I could get was a single click.

After calling Roadside Assistance I remembered this thread, had a quick read on my iPhone on the side of the road and tried staring the car again. (I'd been stopped for about 20 mins by then) and away she went.

Thanks to those who've posted on this thread 

[Cam Arnott]

A footnote to add that I had the starter replaced today along with a new bush for the gearbox. The auto elec checked the wiring harness to the starter and found the lower section of the loom had serious deterioration of the insulation, so stripped it all back and re-did it.

Check your wiring folks!

[jakroo]

good to know Cam, thanks.

[Cam Arnott]

Pics are always more interesting!

IMG_7914 by Cameron Arnott, on Flickr

IMG_7911 by Cameron Arnott, on Flickr

IMG_7912 by Cameron Arnott, on Flickr

[Allan C]

Exactly the same as happened to my 968. Generally I the wiring is not interfered with it will be OK. The Auto Electrician said to me to be very careful with any wiring under the bonnet as the insulation will be very brittle. Had the cam chain hydraulic tension pads checked and the wiring on the hall effect sensor at the back of the head had to be replaced due to brittle insulation.

[OzJustin]

Does anyone have a wiring diagram showing the routing of the battery to alternator cable on a 944? I.e. is it under the car body or in the interior under the carpet?

Can anyone recommend a good auto electrician on Brisbane southside, preferably with Porsche experience? I’m looking to get my corroded cable replaced.