No Start After Clutch Job
05-05-2014, 01:14 PM
#61
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There are so many ways things can go wrong outside of the electronics themselves. Testing in a running car is the simplest solution. I know from conversation that even Specialized ECU uses test cars from time time to validate electronics in real world beyond their bench top simulation. I think the biggest challenge from a troubleshooting perspective is when components and harnesses are exchanged.
In my case, my DME harness looks pretty disheveled in the passenger footwell. There seems to be a lot of extra wire there from a length perspective. Looking at my wiring diagrams the T1 connector on my car should be an 8 pin affair. But it is a 14 pin connector. This size connector in this location didn't appear until MY 90 according to my diagrams. The PO of my car operated a Porsche restoration shop for a number of years. The car I purchased was a "restoration" in progress which the PO just got tired of working on. The PO worked as a professional photographer (self taught) covering primarily F1. He typically had one weekend a month to work on the car. Many new parts had been installed over a 2 year period. In the end the guy just ran out of steam.
When I bough my 951 one of the balance shafts was 180 degrees out of time. The PO didn't discuss it, but the vibration was there on the test drive. When I made my purchase decision, I knew I was "taking a chance". I drove the car from KY to FL betting that I would "make it" (which I did no issues). It took me about 3 hours of studying the balance shafts / documentation, to recognize the mistake. For the most part the PO did high quality work, but the balance shaft issue was something that just got by him. I think balance shaft alignment is a common mistake.
I suspect some of the wiring in my car may not be MY88 based on my review of the wiring diagrams. As long as the right connections are being made in the harness all should be good. This is one of the reasons why I decided to pull my DME harness to verify all connections and inspect every inch of wiring. Every model and MY have their own associated wiring harnesses and electronic components. Component compatibility is easy to establish based on parts lists. But a deeper level challenge exists once people start exchanging / fixing the wires themselves. As these vintage cars continue to be parted out and restored, the opportunities for deeper level issues will only continue to go up.
I do not think Perry is dealing with miss-matched components or harness problems. His problem is most likely electronics failure. If his electronics pass a run test in my car that will be a real surprise given the level of diagnostic Perry has completed. The open question (assuming electronics failure has occurred) is where to go from here. If Perry's situation is like mine, there is a problem with the KLR which likely damaged the DME. Sending them both off to Specialized should mirror my situation (warranty repair of DME, rebuild of KLR). Problem now is that Perry how has ~$700 tied up in electronics. There may be better solutions (cost / benefit) in the market place than just rebuilding stock electronics. Rogue Tuning has some really nice stuff.
I wish I had walked a different path with my no-start, but thats water under the bridge at this point.
- Paul
In my case, my DME harness looks pretty disheveled in the passenger footwell. There seems to be a lot of extra wire there from a length perspective. Looking at my wiring diagrams the T1 connector on my car should be an 8 pin affair. But it is a 14 pin connector. This size connector in this location didn't appear until MY 90 according to my diagrams. The PO of my car operated a Porsche restoration shop for a number of years. The car I purchased was a "restoration" in progress which the PO just got tired of working on. The PO worked as a professional photographer (self taught) covering primarily F1. He typically had one weekend a month to work on the car. Many new parts had been installed over a 2 year period. In the end the guy just ran out of steam.
When I bough my 951 one of the balance shafts was 180 degrees out of time. The PO didn't discuss it, but the vibration was there on the test drive. When I made my purchase decision, I knew I was "taking a chance". I drove the car from KY to FL betting that I would "make it" (which I did no issues). It took me about 3 hours of studying the balance shafts / documentation, to recognize the mistake. For the most part the PO did high quality work, but the balance shaft issue was something that just got by him. I think balance shaft alignment is a common mistake.
I suspect some of the wiring in my car may not be MY88 based on my review of the wiring diagrams. As long as the right connections are being made in the harness all should be good. This is one of the reasons why I decided to pull my DME harness to verify all connections and inspect every inch of wiring. Every model and MY have their own associated wiring harnesses and electronic components. Component compatibility is easy to establish based on parts lists. But a deeper level challenge exists once people start exchanging / fixing the wires themselves. As these vintage cars continue to be parted out and restored, the opportunities for deeper level issues will only continue to go up.
I do not think Perry is dealing with miss-matched components or harness problems. His problem is most likely electronics failure. If his electronics pass a run test in my car that will be a real surprise given the level of diagnostic Perry has completed. The open question (assuming electronics failure has occurred) is where to go from here. If Perry's situation is like mine, there is a problem with the KLR which likely damaged the DME. Sending them both off to Specialized should mirror my situation (warranty repair of DME, rebuild of KLR). Problem now is that Perry how has ~$700 tied up in electronics. There may be better solutions (cost / benefit) in the market place than just rebuilding stock electronics. Rogue Tuning has some really nice stuff.
I wish I had walked a different path with my no-start, but thats water under the bridge at this point.
- Paul
05-05-2014, 10:37 PM
#62
Instructor
Thread Starter
When I started to look for a 944 to buy I was dismayed at the quality of many of the cars for sale. Many had been the victims of misguided attempts to improve performance or botched repair work. While my car was very far from perfect, I recognized that it was a basically decent, unmolested car that had repair/maintanence receipts going back to 1992/40,000 miles. As I began to do some work to the car I was pleasantly surprised by the lack of stipped bolt holes, patched in wiring, wrong sized tires, etc.
Every time that I do any work to any of my cars (including my daily driver Subarus) I am accutely aware that I may be making things worse instead better. When I started the clutch job on the Porsche (by the way, I have had to replace the clutches on all of my current cars) I quickly realized that my work may be making things worse. I ended up not just doing the complicated clutch work but also rebuilding the torque tube--something that I have never done before, not really anything like it. Of all the things that I expected might give me problems, that the car would not start due to some arcane electrical problems did not even enter my worry horizon. And I have a wide worry horizon.
More than anything I am wondering what I could have possibly done to the car during the clutch work that could have caused this problem. I don't think that the computers just "went bad" without some provocation. As I mentioned in a previous post in this thread I don't like the "sh*t happens" philosophy. If my computers are indeed what is prevented the car from starting, I will always drive this car without fully trusting I will never fully understand what cause the no start in the first place.
Perry
Every time that I do any work to any of my cars (including my daily driver Subarus) I am accutely aware that I may be making things worse instead better. When I started the clutch job on the Porsche (by the way, I have had to replace the clutches on all of my current cars) I quickly realized that my work may be making things worse. I ended up not just doing the complicated clutch work but also rebuilding the torque tube--something that I have never done before, not really anything like it. Of all the things that I expected might give me problems, that the car would not start due to some arcane electrical problems did not even enter my worry horizon. And I have a wide worry horizon.
More than anything I am wondering what I could have possibly done to the car during the clutch work that could have caused this problem. I don't think that the computers just "went bad" without some provocation. As I mentioned in a previous post in this thread I don't like the "sh*t happens" philosophy. If my computers are indeed what is prevented the car from starting, I will always drive this car without fully trusting I will never fully understand what cause the no start in the first place.
Perry
05-06-2014, 09:37 AM
#63
Rennlist Member
Is there a way to put your scope on the output of the computer? I.e. to see if the fuel injectors and coil are firing?
Thinking more about it, you did the clutch... so it's likely with the engine movement sensing (speed and ref). Did you leave a washer on the end of a sensor??? Is there something else on the flywheel that's giving it a double signal? You're certain the DC and DG sensors are swapped? You didn't use an aluminum set screw in the flywheel? Set screw is set to the right height? Dowel pin is in the crankshaft indexing the flywheel correctly?
Thinking more about it, you did the clutch... so it's likely with the engine movement sensing (speed and ref). Did you leave a washer on the end of a sensor??? Is there something else on the flywheel that's giving it a double signal? You're certain the DC and DG sensors are swapped? You didn't use an aluminum set screw in the flywheel? Set screw is set to the right height? Dowel pin is in the crankshaft indexing the flywheel correctly?
05-06-2014, 10:27 AM
#64
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Doing a read through of these forums there seem to be peripheral issues appear to trigger electronics issues:
Years ago, I had a no-start after doing a clutch job. It was due to poor connection of the speed sensor signal to the DME computer. I had spark but no fuel injection. With my last no-start I had 2 of 4 plug wires with very poor connections. I also had a several of "dead battery" events because I had a slow drain in the electrical system and didn't use a battery maintainer (my 951 is not my daily driver). With the electrical work I've done (cables / harnesses) it looks like my slow electrical drain is gone. I also bought a battery maintainer and will be using it if required. I would never have connected either of these events with electronics failure until I surfed this forum.
Battery discharge appears to impact the voltage regulators in the computer. Bad plug wires cause overheating of the transistor networks which fire the coil.
Keep fighting the fight - This problem will be solved
- Battery Discharge
- Bad Plug Wires
- Others?
Years ago, I had a no-start after doing a clutch job. It was due to poor connection of the speed sensor signal to the DME computer. I had spark but no fuel injection. With my last no-start I had 2 of 4 plug wires with very poor connections. I also had a several of "dead battery" events because I had a slow drain in the electrical system and didn't use a battery maintainer (my 951 is not my daily driver). With the electrical work I've done (cables / harnesses) it looks like my slow electrical drain is gone. I also bought a battery maintainer and will be using it if required. I would never have connected either of these events with electronics failure until I surfed this forum.
Battery discharge appears to impact the voltage regulators in the computer. Bad plug wires cause overheating of the transistor networks which fire the coil.
Keep fighting the fight - This problem will be solved
05-06-2014, 10:14 PM
#65
Instructor
Thread Starter
Van, Specsalot,
The ignition wires, cap, and resistor plug tops all show the correct resistance. I did this test when I ran through the DME check list last weekend. I had no misfires when the car was running. I don't think I have dead plug wires causing excessive resistance damaging the computer.
During the down time for the car, I would occasionally put on my battery charger on the 2amp setting and let the battery charge for about 20 minutes.
As I have mentioned earlier, years ago the shop where I worked had an Alfa Romeo Spider that would crank strongly, but did not start. After some investigation we accidentally discovered that the car would start when jumped from a deep cycle battery cart we had at the shop. We solved out customer's problem by simply and cheaply installing a new, good quality battery.
One of the test points mentions that the cranking voltage must be above 10.2 volts. I get 10.8 to 11.1 during cranking. I also took my battery to a local Wal-Mart and they put their tester on it and it passed the cranking voltage test with flying colors. Should the computers come back having worked in another 951 I will replace the battery as the next most likely possible source of the no start.
Perry
The ignition wires, cap, and resistor plug tops all show the correct resistance. I did this test when I ran through the DME check list last weekend. I had no misfires when the car was running. I don't think I have dead plug wires causing excessive resistance damaging the computer.
During the down time for the car, I would occasionally put on my battery charger on the 2amp setting and let the battery charge for about 20 minutes.
As I have mentioned earlier, years ago the shop where I worked had an Alfa Romeo Spider that would crank strongly, but did not start. After some investigation we accidentally discovered that the car would start when jumped from a deep cycle battery cart we had at the shop. We solved out customer's problem by simply and cheaply installing a new, good quality battery.
One of the test points mentions that the cranking voltage must be above 10.2 volts. I get 10.8 to 11.1 during cranking. I also took my battery to a local Wal-Mart and they put their tester on it and it passed the cranking voltage test with flying colors. Should the computers come back having worked in another 951 I will replace the battery as the next most likely possible source of the no start.
Perry
05-06-2014, 10:38 PM
#66
Instructor
Thread Starter
Van,
There is no way to test the output of the DME computer except at the connection to the KLR. The DME fails this test.
The flywheel has an asymmetrical dowel hole that lines up with a pin in the back of the crank. So there is no way I could have wrongly installed the flywheel. Neither I nor the machine shop disturbed the pins on the circumference of the flywheel. The speed sensor has the figure "8" washer installed correctly, and I gapped the sensor correctly.
The problem here is that I get nothing, not an occasional pop from a mis-timed spark plug firing, not a wiff of gas from the exhaust tailpipe. It was only when I screwed around with powering the DME intermittently did I get anything from the ignition system or fuel system, and then only randomly. All the test I've thrown at the speed/reference sensor have come back as a pass. While these sensors are the source of so many no starts, and while I did screw with them as part of the clutch work, I just don't see that they could be causing this problem.
Perry
There is no way to test the output of the DME computer except at the connection to the KLR. The DME fails this test.
The flywheel has an asymmetrical dowel hole that lines up with a pin in the back of the crank. So there is no way I could have wrongly installed the flywheel. Neither I nor the machine shop disturbed the pins on the circumference of the flywheel. The speed sensor has the figure "8" washer installed correctly, and I gapped the sensor correctly.
The problem here is that I get nothing, not an occasional pop from a mis-timed spark plug firing, not a wiff of gas from the exhaust tailpipe. It was only when I screwed around with powering the DME intermittently did I get anything from the ignition system or fuel system, and then only randomly. All the test I've thrown at the speed/reference sensor have come back as a pass. While these sensors are the source of so many no starts, and while I did screw with them as part of the clutch work, I just don't see that they could be causing this problem.
Perry
05-07-2014, 01:31 PM
#67
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Perry,
I tried to call you today with these results but could not get through. I plugged your electronics into my car this morning. My car did not start. Here were the observations I made:
What I did note (with the grounded plug in the coil war) was that spark would take place when moving from IGNITION KEY OFF to KEY ON. It was a healthy spark. But no coil sparking took place during engine cranking. In my view this information points toward DME issues.
It is interesting to note that in your vehicle, you are not seeing spark or fuel injection. I'm not sure why I see fuel injection and you do not. Perhaps your DME relay is not operating correctly. It is more likely that the second stage of the DME control circuit is not a complete circuit. My read of the prints is that the second stage DME relay coil is supplied with B+ at Terminal 87. The circuit completes to ground in the Motronic DME at TERMINAL 20. This ground path passes through DME CONNECTION T21 lead 5. This is the 14 pin connector on drivers side near the firewall.
I wish I could have given you better news. Send me a PM with next steps.
-Paul
I tried to call you today with these results but could not get through. I plugged your electronics into my car this morning. My car did not start. Here were the observations I made:
- Fuel Injection was taking place - Fuel smell clearly evident after a very short crank period.
- No Spark - Pulled coil wire and inserted a grounded spark plug into the end - no repetitive sparking.
- No Tach Bounce
- Disconnected the KLR and jumped KLR plug pins 9-16 (per manual) - still no start. Fuel injection was taking place, but no spark.
What I did note (with the grounded plug in the coil war) was that spark would take place when moving from IGNITION KEY OFF to KEY ON. It was a healthy spark. But no coil sparking took place during engine cranking. In my view this information points toward DME issues.
It is interesting to note that in your vehicle, you are not seeing spark or fuel injection. I'm not sure why I see fuel injection and you do not. Perhaps your DME relay is not operating correctly. It is more likely that the second stage of the DME control circuit is not a complete circuit. My read of the prints is that the second stage DME relay coil is supplied with B+ at Terminal 87. The circuit completes to ground in the Motronic DME at TERMINAL 20. This ground path passes through DME CONNECTION T21 lead 5. This is the 14 pin connector on drivers side near the firewall.
I wish I could have given you better news. Send me a PM with next steps.
-Paul
05-07-2014, 09:59 PM
#68
Instructor
Thread Starter
Specsalot,
I sent you an email at your gmail account.
Let's give this some thought. It is very unlikely that my orginal DME and then a rebuilt one from Specialized both went suddenly bad, one right after the other. What would cause damage to the DME? Could the main ground cable, the one that goes from the B- terminal, through the firewall, then connects to the top of the bell housing, be bad? I have cleaned both the battery and bell housing ends, thoroughly. All the other electrical systems seem to work. The engine cranks strongly.
How could I test the capacity of this ground cable?
Could the battery have an internal short that would damage the DME?
Specsalot had a bad KLR that damaged the DME. Could that be what's happened here? What would damage the KLR?
Any thoughts?
Thanks again to all the people following this tread, and thanks to Specsalot for doing this test.
Perry
I sent you an email at your gmail account.
Let's give this some thought. It is very unlikely that my orginal DME and then a rebuilt one from Specialized both went suddenly bad, one right after the other. What would cause damage to the DME? Could the main ground cable, the one that goes from the B- terminal, through the firewall, then connects to the top of the bell housing, be bad? I have cleaned both the battery and bell housing ends, thoroughly. All the other electrical systems seem to work. The engine cranks strongly.
How could I test the capacity of this ground cable?
Could the battery have an internal short that would damage the DME?
Specsalot had a bad KLR that damaged the DME. Could that be what's happened here? What would damage the KLR?
Any thoughts?
Thanks again to all the people following this tread, and thanks to Specsalot for doing this test.
Perry
05-08-2014, 02:05 AM
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Specsalot,
I sent you an email at your gmail account.
Let's give this some thought. It is very unlikely that my orginal DME and then a rebuilt one from Specialized both went suddenly bad, one right after the other. What would cause damage to the DME? Could the main ground cable, the one that goes from the B- terminal, through the firewall, then connects to the top of the bell housing, be bad? I have cleaned both the battery and bell housing ends, thoroughly. All the other electrical systems seem to work. The engine cranks strongly.
How could I test the capacity of this ground cable?
Could the battery have an internal short that would damage the DME?
Specsalot had a bad KLR that damaged the DME. Could that be what's happened here? What would damage the KLR?
Any thoughts?
Thanks again to all the people following this tread, and thanks to Specsalot for doing this test.
Perry
I sent you an email at your gmail account.
Let's give this some thought. It is very unlikely that my orginal DME and then a rebuilt one from Specialized both went suddenly bad, one right after the other. What would cause damage to the DME? Could the main ground cable, the one that goes from the B- terminal, through the firewall, then connects to the top of the bell housing, be bad? I have cleaned both the battery and bell housing ends, thoroughly. All the other electrical systems seem to work. The engine cranks strongly.
How could I test the capacity of this ground cable?
Could the battery have an internal short that would damage the DME?
Specsalot had a bad KLR that damaged the DME. Could that be what's happened here? What would damage the KLR?
Any thoughts?
Thanks again to all the people following this tread, and thanks to Specsalot for doing this test.
Perry
Battery problems typically cause a drop in terminal voltage under load. Each battery cell has a nominal internal resistance which is why terminal voltage drops when load is placed on a battery. A shorted cell will cause a drop in unloaded terminal voltage. A more common problem is that a cell develops higher internal resistance. This causes a larger than normal voltage drop under load. The voltages you describe do not suggest you are having any battery issues. You had "load test" done on your battery. Any major flaws would have been identified in that test. Electronics can be damaged by low voltages because with lower voltages present, component current levels go up. In this context "low" means voltages quite a bit lower than you are reporting. I also think they have to be low for some time to cause overheat failures.
FWIW, when I did my clutch job, I decided to slot my bell housing like you did. It hasn't seemed to have caused any issues in my car. You mentioned this in one of your posts, but I think you can forget about it as far as your problem goes.
I wish I could provide more details on the nature of my electronics failure. The tech at Specialized assured me that it was a failure in the KLR that took out my rebuilt DME. He said that the signal level from the KLR to the DME was too high a voltage which damaged transistors and capacitors in my spark circuits. He assured me that the issue was internal to the KLR and not an external issue. When I first installed my rebuild DME, I had weak spark (no start). Over about 4 or 5 attempts a troubleshooting (which included test cranking), my conditions went from weak spark to NO SPARK. So what seems clear is that major damage occurred to my DME on first start attempt. It took a number of other sessions to fully kill the spark generating circuits.
Why your electronics in my car showed fuel injection, but not in your car is an important piece of information. It says to me that something else is wrong with your car as compared to mine. Not sure what it could be though. By implication, perhaps the actual voltage supply to your injectors is having issues.
The first stage of your DME relay (terminals 30 [in] and 87 [out]) is what supplies B+ to the common side of your injectors and timing valve. This power is passed through the 14 pin connector by your brake booster through PIN 2. Makes me wonder if you are having harness issues getting B+ to your injectors themselves? If you haven't checked your injector wiring under the connector boots, it might be worth a look. When I worked at my 2010 no-start, I found major insulation problems under the boots of the connectors of all 4 injectors. I'm not sure it was a factor in my 2010 no-start, but it wasn't pretty.
Good Luck - Keep posting efforts and progress.
05-21-2014, 06:05 PM
#70
Instructor
Thread Starter
For Those Still Following This Thread…
I sent both my KLR and me DME off to Specialized ECU Repair for them to test. Their report states that the KLR is defective, and that this defect damaged the DME. The DME is one of their exchange ones. They agreed to cover the DME repair under warranty and the repair the KLR for $350.
I will report back once the computers have returned to me.
Perry
I sent both my KLR and me DME off to Specialized ECU Repair for them to test. Their report states that the KLR is defective, and that this defect damaged the DME. The DME is one of their exchange ones. They agreed to cover the DME repair under warranty and the repair the KLR for $350.
I will report back once the computers have returned to me.
Perry
05-21-2014, 10:40 PM
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Well that stinks for sure. Hopefully things will go VROOOOM when you plug up the repaired electronics. I still don't see any direct connection between doing a clutch job and the issue you've had. I would love to hear from someone who could connect those dots.
05-22-2014, 09:21 AM
#72
Instructor
Thread Starter
Specsalot,
Yes, I was not happy with this news, but hope that the car will be up and running without alot more work.
Yes, if anyone can connect the dots of the clutch job and this no start, I would be greatful. I would like to know why this happened so that I can avoid doing it again!
Specsalot, if I haven't been effusive enough in my appreciation, let me tell you again how much your help and advice made this ordeal go by quicker and with much less anxiety. Thank you.
Perry
Yes, I was not happy with this news, but hope that the car will be up and running without alot more work.
Yes, if anyone can connect the dots of the clutch job and this no start, I would be greatful. I would like to know why this happened so that I can avoid doing it again!
Specsalot, if I haven't been effusive enough in my appreciation, let me tell you again how much your help and advice made this ordeal go by quicker and with much less anxiety. Thank you.
Perry