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Euro 95 993 Is Drive Block causing this non-start issue?

Apologies in advance for a long post- but the background could be important.

After reading many posts on both Rennlist and Pelican I am still at a loss trying to get my car to start.
Some time ago my wife had the car, a 1995 993 C4, to commute to work. The drive in went perfectly and on the way home she stopped to refuel. As she was rejoining the motorway and just shifting into third gear the engine quit. She managed to pull off to the side of the road where she tried several times to re-start with no luck. The car was then recovered and dropped off on our driveway. I came home from work about 4-5 hours later and we decided to put it in the garage so I could investigate. We were ready to push it in, but decided to see if it would start and happily it did so she drove it in. It has not ever started since then. It will crank, but it will not start.
Upon initial investigation I found that I wasn't getting any spark. At this point I verified the DME relay was working and even bought another one just to double check that this item was not to blame. I was able to also perform some checks at the DME connector to verify I was getting readings that were correct. I even had a thread on Rennlist for this, here's the link, https://rennlist.com/forums/993-forum/998726-no-trouble-codes-no-spark-no-start-95-993-c4.html
As time went by I ran out of ideas so I hired an automotive electrician to come and fix the car. He visited my car on 3 occasions for several hours each time and never could figure out what was wrong. Finally, he stopped answering his phone when I called.
Next step was to have it sent to the nearest Porsche Service Center as I figured they will have the correct diagnostic tools to find the problem. Well, after 5 weeks with them we are no nearer to solving the problem. They have verified the alarm control unit is OK by replacing it temporarily with a brand new module and the DME has been sent out to an independent shop for testing and come back as OK with no faults. However, they now suggest that replacing the DME is the solution to my problem, which to me doesn't make sense.
But, does it make sense that the drive block could be the culprit here? Would performing the immobilizer bypass procedure method suggested by Bill Verburg in this forum possibly solve this issue since the electricians and Porsche Master Technicians haven't found anything else wrong?
The Motronic Unit is 993.618.124.04 , 0.261.203.675.
Any ideas out there?
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David Dolan
1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-07-2018, 10:43 PM
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Further information today from the Porsche Service Center stating that the feeds going into the DME are OK, but the feeds coming out are not OK.

Another call to a company that rebuilds DMEs and the guy there said the unit can indeed check out OK, but if the Immobilizer signal is wrong then it will not start.
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-08-2018, 03:29 AM
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It's common for the DME solder points to go bad, I've had DME's rebuilt by ECU Doctors very competent and quick.

As to the immobilizer, If the immobilizer is bad, which is possible, ECU Doctors also does them

You can by pass it but to do so 2 things need to be done
1)the chip in the DME needs to be replaced w/ a chip that does not expect an immobilizer signal.
2) the R61 relay needs to be by passsed, see this thread
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Old 03-08-2018, 03:52 AM
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Quote:
Originally Posted by Bill Verburg View Post
It's common for the DME solder points to go bad, I've had DME's rebuilt by ECU Doctors very competent and quick.

As to the immobilizer, If the immobilizer is bad, which is possible, ECU Doctors also does them

You can by pass it but to do so 2 things need to be done
1)the chip in the DME needs to be replaced w/ a chip that does not expect an immobilizer signal.
2) the R61 relay needs to be by passsed, see this thread
Today I've ordered a Steve Wong chip for this very reason.
The relay will also be ordered.

However, is it possible for a DME to check out as OK and still have bad solder points?
And, if I install those items I assume the condition of the immobilizer is no longer something to worry about?
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David Dolan
1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-08-2018, 03:58 AM
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Quote:
Originally Posted by david dolan View Post
Today I've ordered a Steve Wong chip for this very reason.
The relay will also be ordered.

However, is it possible for a DME to check out as OK and still have bad solder points?
And, if I install those items I assume the condition of the immobilizer is no longer something to worry about?
The usual cold solder issue is an intermittent cutout on bumps or rough road, gradually gets worse. So your issue may be different.

Yes, At least on my '95 and 2 others that we've done that to. The immobilizer is irrelevant, remote locks and alarm still work in the usual way.
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Old 03-08-2018, 05:08 AM
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Quote:
Originally Posted by david dolan View Post
Today I've ordered a Steve Wong chip for this very reason.
The relay will also be ordered.

However, is it possible for a DME to check out as OK and still have bad solder points?
And, if I install those items I assume the condition of the immobilizer is no longer something to worry about?
I did this to my immobilized 95. Best $ Iíve spent on it yet.
Old 03-08-2018, 07:09 AM
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Quote:
Originally Posted by wesleyc View Post
I did this to my immobilized 95. Best $ Iíve spent on it yet.
Glad to hear that, hopefully it will be what fixes my car too!
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-08-2018, 08:40 AM
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Yes I just sent an RS ECU that I ourchased almost ten years back thinking it was a non immobilizer
OBD-1 unit that once checked by ECU Specialists it was determined it did actually have the drive
block option .
Easily bypassed have yet to try it but wasn't very expensive ... Bert
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Old 03-09-2018, 04:07 PM
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If you are facing non-start issues with the car, it could be due to the drive block causing troubles. However, there could be other reasons too. And to ensure that you knowthis well enough, you can consult the user manual of your car.
And suppose if you lost the user manual, you can get a copy of it for free on the online website manuals.co.
Old 03-12-2018, 04:16 AM
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Well, I'm a step closer with the arrival of the Steve Wong chip. Interestingly, I had the situation where the notched chip end was facing in the opposite direction of the notch in the chip carrier. This is in direct conflict with the written instructions included with the chip and on his website. After a short email exchange he told me it should face the same direction as the original chip did. This was the obvious answer, but as the Porsche Service Center had sent the DME out for testing the previous week and that had also been mentioned by the DME repair Centre I wanted to make sure they hadn't rotated the original chip's orientation.
Anyway, here are some before and after shots as I'm still waiting for the fuse box relay to arrive to complete the elimination of the immobilizer from the start sequence.

Just after opening the DME this is what you see.



Close up of the original chip, note the notch on the left end.



As you can see the chip carrier has a notch facing the other direction(towards the circled 30).



Steve Wong's chip now installed with the notch to the left.



Last shot with the outer clip attached to secure the chip installation.

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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-13-2018, 11:03 PM
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My relay has arrived now too, so next thing to do is get this back to the Porsche service center and see if the car starts.






I do have a question though as I have been re-reading Adrian Streather's 993 book and in the Alarm, Immobilizer and intergrated central locking system section he states if the anti-drive-off feature is activated when the alarm system is armed the ignition and injection systems are disabled. He also notes that when relay 61 is disabled no power is available to the starter motor solenoid.

I am a bit worried about that statement as I have always been able to crank the engine, so it might be I am not actually going to solve the problem. Is there ever a state where the immobilizer could prevent starting and still allow the starter to turn the engine over?
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-18-2018, 04:05 AM
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OK, reading in Adrian Streather's Engine section I find another list which shows that the engine CAN turn over and you can still have an immobilizer fault, hmm.



So all hope is not lost that the new chip and relay might do the trick!
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-18-2018, 05:04 AM
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Well, not completely surprised by the result however I was disappointed when I received the call from the Porsche center that after installing the DME and relay the car has still not come back to life.
I've asked them to look at some suspicious wiring in the fuse-box now, I am concerned the aftermarket alarm had not been completely removed-as in some wiring that is not-factory could be interfering with the starting procedure.
I'm starting to believe that this is going to be something really basic in the end, such as a loose or broken wire connection. Fingers are crossed that they find it with a few more hours of investigation.
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-22-2018, 12:01 AM
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Another suggestion I've had from the Porsche Service Technician is the idea of temporarily replacing my DME with another one that is known to be working just to 100% rule out any question of doubt over my DME. The Porsche technician said they just don't see that many 993's in the service center anymore so this is not something he's been able to do so far.

Does anyone know what DME's would be OK to try based on the original DME part number, 993.618.124.04 , 0.261.203.675.?
Also bearing in mind that I have just replaced my factory chip with a Steve Wong non-drive block chip and the R61 relay as suggested by Bill Verburg.


Would really appreciate some input as with this information I can put out a request for help with the Porsche Club here in the UK.

Thank you!
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-26-2018, 03:22 AM
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Quote:
I am concerned the aftermarket alarm had not been completely removed-as in some wiring that is not-factory could be interfering with the starting procedure.
That certainly complicates things, Lord only knows what wiring changes were done to that car.

Does the Porsche dealer say whether it's fuel or spark that is missing?

It's much harder to diagnose these days but back in the day you generally checked for those 2 things first
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Old 03-26-2018, 11:58 AM
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Quote:
Originally Posted by Bill Verburg View Post
That certainly complicates things, Lord only knows what wiring changes were done to that car.

Does the Porsche dealer say whether it's fuel or spark that is missing?

It's much harder to diagnose these days but back in the day you generally checked for those 2 things first
Indeed, I had a long conversation today with the Porsche technician and he agreed that the next step would be to remove all the non-factory wiring changes that were currently complicating things in the fuse-box panel. He will remove all that wiring and investigate and repair as required to eliminate them from the list of possible causes of this problem.

He stated that in his experience this problem generally gets solved once the DME is replaced, however they are thin on the ground. I'd have to buy or borrow another one to test this idea. The nearest new DME is in Germany and it's about $5000 from the dealer.

I know we aren't achieving a spark at the coils, the mechanic stated that not all the grounds are giving the signals that the DME wants and so the coils are not getting energized. He also said that he tested the fuel pump and it works just like I had also found, but he said he was still a little suspicious. I'd say we believe currently that it's spark that is missing, but he's keeping his options open.

I asked if it would be possible to simulate the correct signals from the grounds to see if the engine would then start, but he said it would be too complicated as there are multiple grounds that would all need to be jumpered and his worry was that any mistake could fry the electronics.

In any case I could possibly reach out to some club members in the UK forums if I knew all the compatable DME's for my car.
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1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 03-26-2018, 12:25 PM
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After 3 months at the dealer I finally had to pull the car out and send it to an independent garage as I just wasn't getting the car repaired quickly enough. The new garage had not one but two other 95 993's in for work so in just one day there were 2 other cars to test my DME with. My DME was swapped into one of the other cars and it immediately started up! So DME is OK! The ignition module was also swapped over and the same result was had...the car started right up.
The new shop has a few ideas regarding either position sensors or hall sensors, if those are OK then it's down to wiring issues. I have a much better feeling from them that they will get to the bottom of this issue sooner rather than later now. I'll keep posting as results come in.
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Old 05-15-2018, 12:35 AM
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Because I hate a thread without an ending I'm glad to finally report the car has finally started again!

Turned out to be the Crankshaft Position Sensor which I had previously checked with a multi-meter at the DME terminals. If you've read my thread in Rennlist I had a reading that was a little bit under the recommended range, however another forum member suggested this was close enough to be considered OK. Even so, what had happened was that the plastic the CPS is made of had become so old that it started to crumble. When this happened it became loose in it's bracket eventually causing the gap between it and the bump on the flywheel to disappear. What happened next of course was there was an impact to the sensor by the flywheel.

Just goes to show an electrical signal can be OK, or nearly OK and if you don't do a physical inspection you might be sorry. This solution took many months to find because of not looking at the parts more closely.

Positives to take away from this experience, a bit better understanding of the electrical system, a Steve Wong Chip, elimination of a secondary alarm, elimination of the drive block immobilizer and an independent garage that solved a problem rather quickly.

Negatives, the Porsche dealer service centre didn't find what in the opinion of the second garage was one of the first things they should've checked. I didn't find it either on my initial investigations, nor did the Automotive Electrician that visited my home 3 times.
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1979 911 SC Targa Metallic Black
Old 05-20-2018, 09:53 PM
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Warning graphic photos!

Thought I would post the photographic evidence of a battered Crank Position Sensor.






No wonder the car wouldn't start!
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David Dolan
1995 993 Carrera 4 India Red
1979 911 SC Targa Metallic Black
Old 05-30-2018, 03:37 AM
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