No-start situation resolved!(EDIT: still don't know why)
06-16-2006, 11:54 AM
#1
Addict
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Mar 2003
Location: South of the St-Lawrence river
Posts: 1,498
Likes: 0
Received 1 Like
on
1 Post
No-start situation resolved!(EDIT: still don't know why)
EDIT: I started this thread after experiencing a failure to crank over the engine after installing the LR injector/knock sensor harness. I initially thought that the issue was caused by the a bad injector connector on the new harness (you can see pictures of this in my first post). But then last night Chris Prack objected to my explanation. His arguments made a lot of sense and after spending a few hours looking at the electrical schematics I had to come to the same conclusion that the faulty injector connection was not responsible for the no-crank situation.
Last week-end, after installing the new LR fuel rail, new LR SS braided fuel lines, and new injector/knock sensor harness, I tried to fire up the car. As soon as I turned the key to “start” all I heard was “click-click-click” and then nothing. The starter never spinned, plus when I immediately tried to restart there was absolutely no sound and the instrument lights did not even turn on. My immediate thought was: Shorted connection to the starter or bad starter.
I had replaced the starter last August and so I was skeptical that the starter itself could be at fault. So, I checked the battery. It had good voltage. Later, this week I decide to remove the starter and also check the starter connections. The connections all seemed perfect, but I still pulled the starter out of the car. I also pulled the battery and then using jumper cables to the starter, I tested it. Lo and behold it spinned perfectly.
This morning, I hooked the starter and the battery back up. Using a digital multimeter, I then proceeded to test a number of connections to the DME and KLR. First, I tested pins 35 to 5 on the DME plug for battery voltage. I had voltage. Then I tested, 18 to 5 and I also had voltage. Next, I tested pins 14 to 6 on the KLR plug and also had voltage.
Since, I had put in a new injector harness, I then proceeded to test voltage to the injector plugs. So I pulled the plugs and put the multimeter leads to the plug for cylinder 4 and I had voltage. Then, I tested on cylinder 3 and had voltage. When, I tried to put the leads in the pins for cylinder 2, this is what I found:
The black wire pin was not seated! I pulled off the blue sleeving insulation and there was no tension holding the black wire in place! Looking closer at the pin I noticed that the locking tab was turned up almost 180 degrees.
This prevented the pin from seating completely into the plastic connector. So I carefully unbent (sic) it back and was then able to push the pin completely into the connector so that it could lock in place.
So, because the pin on injector two was not fully seated, as soon as starting voltage was applied, the current had no where to go and it would short the system, preventing the starter from receiving its juice. I plugged everything back in, turned on the ignition and the engine cranked immediately.
I still have a problem with speed and reference sensor connectors. I'm waiting on the new ones I ordered from EagleDay.com.
Last week-end, after installing the new LR fuel rail, new LR SS braided fuel lines, and new injector/knock sensor harness, I tried to fire up the car. As soon as I turned the key to “start” all I heard was “click-click-click” and then nothing. The starter never spinned, plus when I immediately tried to restart there was absolutely no sound and the instrument lights did not even turn on. My immediate thought was: Shorted connection to the starter or bad starter.
I had replaced the starter last August and so I was skeptical that the starter itself could be at fault. So, I checked the battery. It had good voltage. Later, this week I decide to remove the starter and also check the starter connections. The connections all seemed perfect, but I still pulled the starter out of the car. I also pulled the battery and then using jumper cables to the starter, I tested it. Lo and behold it spinned perfectly.
This morning, I hooked the starter and the battery back up. Using a digital multimeter, I then proceeded to test a number of connections to the DME and KLR. First, I tested pins 35 to 5 on the DME plug for battery voltage. I had voltage. Then I tested, 18 to 5 and I also had voltage. Next, I tested pins 14 to 6 on the KLR plug and also had voltage.
Since, I had put in a new injector harness, I then proceeded to test voltage to the injector plugs. So I pulled the plugs and put the multimeter leads to the plug for cylinder 4 and I had voltage. Then, I tested on cylinder 3 and had voltage. When, I tried to put the leads in the pins for cylinder 2, this is what I found:
The black wire pin was not seated! I pulled off the blue sleeving insulation and there was no tension holding the black wire in place! Looking closer at the pin I noticed that the locking tab was turned up almost 180 degrees.
This prevented the pin from seating completely into the plastic connector. So I carefully unbent (sic) it back and was then able to push the pin completely into the connector so that it could lock in place.
So, because the pin on injector two was not fully seated, as soon as starting voltage was applied, the current had no where to go and it would short the system, preventing the starter from receiving its juice. I plugged everything back in, turned on the ignition and the engine cranked immediately.
I still have a problem with speed and reference sensor connectors. I'm waiting on the new ones I ordered from EagleDay.com.
Last edited by 951Porschiste; 06-17-2006 at 04:06 PM.
06-16-2006, 02:48 PM
#3
UAE Rennlist Ambassador
Rennlist Member
Rennlist Member
I had the same issue, but with the knock sensor. But i ordered the connector housings, pins and boot from www.vehicle-wiring-products.co.uk
06-16-2006, 03:24 PM
#5
Burning Brakes
Join Date: Mar 2006
Location: Orlando,FL (formerly UK)
Posts: 1,215
Likes: 0
Received 0 Likes
on
0 Posts
Good work!
-Although as a point of semantics, this was not a "short". It was an "open".
A "Short circuit" is defined as when a conductive element comes into contact with another conductive part of the circuit (which it's not usually supposed to come into contact with). An "Open circuit" is defined as when a conductive element loses connection to another conductive part of the circuit (which it's usually supposed to be connected to).
Since short circuits are often intermittent, people have become used to using the word "short" or the phrase "shorting out" to mean intermittent operation of a connection, but the use of these terms is actually quite wrong. There are indeed intermittent 'shorts' and intermittent 'opens', but there are also permenent shorts and permanent opens.
In this case it was a permanent open circuit, unless of course it sometimes made contact, in which case it would be an intermittent open. -I mention the distinctions specifically because most manufacturers now use a distinction between short circuit and open circuit when reporting fault codes, and for as long a people think that "Short = intermittent" then there will be confusion.
Good detective work though, and excellently informative pictures of a real-world failure for others to use when troubleshooting!
-Although as a point of semantics, this was not a "short". It was an "open".
A "Short circuit" is defined as when a conductive element comes into contact with another conductive part of the circuit (which it's not usually supposed to come into contact with). An "Open circuit" is defined as when a conductive element loses connection to another conductive part of the circuit (which it's usually supposed to be connected to).
Since short circuits are often intermittent, people have become used to using the word "short" or the phrase "shorting out" to mean intermittent operation of a connection, but the use of these terms is actually quite wrong. There are indeed intermittent 'shorts' and intermittent 'opens', but there are also permenent shorts and permanent opens.
In this case it was a permanent open circuit, unless of course it sometimes made contact, in which case it would be an intermittent open. -I mention the distinctions specifically because most manufacturers now use a distinction between short circuit and open circuit when reporting fault codes, and for as long a people think that "Short = intermittent" then there will be confusion.
Good detective work though, and excellently informative pictures of a real-world failure for others to use when troubleshooting!
06-16-2006, 04:24 PM
#6
Addict
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Mar 2003
Location: South of the St-Lawrence river
Posts: 1,498
Likes: 0
Received 1 Like
on
1 Post
Originally Posted by VWaddict
Good work!
-Although as a point of semantics, this was not a "short". It was an "open".
A "Short circuit" is defined as when a conductive element comes into contact with another conductive part of the circuit (which it's not usually supposed to come into contact with). An "Open circuit" is defined as when a conductive element loses connection to another conductive part of the circuit (which it's usually supposed to be connected to).
Since short circuits are often intermittent, people have become used to using the word "short" or the phrase "shorting out" to mean intermittent operation of a connection, but the use of these terms is actually quite wrong. There are indeed intermittent 'shorts' and intermittent 'opens', but there are also permenent shorts and permanent opens.
In this case it was a permanent open circuit, unless of course it sometimes made contact, in which case it would be an intermittent open. -I mention the distinctions specifically because most manufacturers now use a distinction between short circuit and open circuit when reporting fault codes, and for as long a people think that "Short = intermittent" then there will be confusion.
Good detective work though, and excellently informative pictures of a real-world failure for others to use when troubleshooting!
-Although as a point of semantics, this was not a "short". It was an "open".
A "Short circuit" is defined as when a conductive element comes into contact with another conductive part of the circuit (which it's not usually supposed to come into contact with). An "Open circuit" is defined as when a conductive element loses connection to another conductive part of the circuit (which it's usually supposed to be connected to).
Since short circuits are often intermittent, people have become used to using the word "short" or the phrase "shorting out" to mean intermittent operation of a connection, but the use of these terms is actually quite wrong. There are indeed intermittent 'shorts' and intermittent 'opens', but there are also permenent shorts and permanent opens.
In this case it was a permanent open circuit, unless of course it sometimes made contact, in which case it would be an intermittent open. -I mention the distinctions specifically because most manufacturers now use a distinction between short circuit and open circuit when reporting fault codes, and for as long a people think that "Short = intermittent" then there will be confusion.
Good detective work though, and excellently informative pictures of a real-world failure for others to use when troubleshooting!
Thanks for clarifying and of course you are right; the circuit was indeed open. I would really like to understand why this open circuit prevented electricity from 1. reaching the starter and 2. Once it happened almost every other connection in the car went dead (except for the digi clock!).
Regards,
Andre
Trending Topics
06-16-2006, 06:34 PM
#8
Burning Brakes
Join Date: Mar 2006
Location: Orlando,FL (formerly UK)
Posts: 1,215
Likes: 0
Received 0 Likes
on
0 Posts
Yeah, that's the wierd thing...
This is supposition and conjecture, but on my '99 VW, the ECU computer checks continuously for continuity through the injectors. If it detects a fully-open or hard-short condition, it could decide not to run the motor because the motor's not in a ready condition to be run.
I really don't know how the 951 makes those decisions, but is the starter motor solenoid run straight from the key, or through the DMU? -If it's through the DMU then it's entirely possible that it -and anything else which required DMU "authorisation" could be disabled.
Basically the injectors are not unlike airbags. There's a coil which has a very low DC resistance. WHen enough current is pushed through the coil, it performs it's function, but if you 'trickle' a tiny amount of current through it at all times, you can test it's readiness. (Remember, current is different from voltage: a DVM reading the prescence of voltage is a very high-impedance device, and a high-current voltage source will read the same as a current-limited [high resistance] voltage source, so a DVM won't really tell you all that much unless you have the injector connected while you take the reading.)
Airbag controllers do this all the time. They trickle a tiny current through the circuit at all times so that if there's EVER any intermittnet connection problem -be it a momentary hard-short-to-ground or a momentary open connection, it lights the airbag warning light. -that way it can be certain that when an accident occurs, the integrity of the system was always assured to be good, right up to the moment of impact.
The same method can be applied to injectors. -I cannot say for sure that it IS employed on the 944/951, but you raise a fascinating point, and the test would be very simple: -Now that the offending injector mating connection has been repaired; unplug the offending connector and try to start the car again. If it does the same "click but no start" as before, re-connect it. If it goes back to normal, we've learned that the DMU (presumably) appears to perform a potentially disabling continuity check. -That knowledge might be very valuable when diagnosing similar symptoms in the future.
I'd be most interested to see what happens if you do the test. I'm in my VW at the moment and not back with my 951 for a day or two, but if you haven't tried before then, I could try it myself. -Which injector was it, -did you already post that... -I don't recall.
Cheers!
Keith
This is supposition and conjecture, but on my '99 VW, the ECU computer checks continuously for continuity through the injectors. If it detects a fully-open or hard-short condition, it could decide not to run the motor because the motor's not in a ready condition to be run.
I really don't know how the 951 makes those decisions, but is the starter motor solenoid run straight from the key, or through the DMU? -If it's through the DMU then it's entirely possible that it -and anything else which required DMU "authorisation" could be disabled.
Basically the injectors are not unlike airbags. There's a coil which has a very low DC resistance. WHen enough current is pushed through the coil, it performs it's function, but if you 'trickle' a tiny amount of current through it at all times, you can test it's readiness. (Remember, current is different from voltage: a DVM reading the prescence of voltage is a very high-impedance device, and a high-current voltage source will read the same as a current-limited [high resistance] voltage source, so a DVM won't really tell you all that much unless you have the injector connected while you take the reading.)
Airbag controllers do this all the time. They trickle a tiny current through the circuit at all times so that if there's EVER any intermittnet connection problem -be it a momentary hard-short-to-ground or a momentary open connection, it lights the airbag warning light. -that way it can be certain that when an accident occurs, the integrity of the system was always assured to be good, right up to the moment of impact.
The same method can be applied to injectors. -I cannot say for sure that it IS employed on the 944/951, but you raise a fascinating point, and the test would be very simple: -Now that the offending injector mating connection has been repaired; unplug the offending connector and try to start the car again. If it does the same "click but no start" as before, re-connect it. If it goes back to normal, we've learned that the DMU (presumably) appears to perform a potentially disabling continuity check. -That knowledge might be very valuable when diagnosing similar symptoms in the future.
I'd be most interested to see what happens if you do the test. I'm in my VW at the moment and not back with my 951 for a day or two, but if you haven't tried before then, I could try it myself. -Which injector was it, -did you already post that... -I don't recall.
Cheers!
Keith
06-16-2006, 08:36 PM
#9
Addict
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Mar 2003
Location: South of the St-Lawrence river
Posts: 1,498
Likes: 0
Received 1 Like
on
1 Post
Originally Posted by VWaddict
Yeah, that's the wierd thing...
This is supposition and conjecture, but on my '99 VW, the ECU computer checks continuously for continuity through the injectors. If it detects a fully-open or hard-short condition, it could decide not to run the motor because the motor's not in a ready condition to be run.
I really don't know how the 951 makes those decisions, but is the starter motor solenoid run straight from the key, or through the DMU? -If it's through the DMU then it's entirely possible that it -and anything else which required DMU "authorisation" could be disabled.
Basically the injectors are not unlike airbags. There's a coil which has a very low DC resistance. WHen enough current is pushed through the coil, it performs it's function, but if you 'trickle' a tiny amount of current through it at all times, you can test it's readiness. (Remember, current is different from voltage: a DVM reading the prescence of voltage is a very high-impedance device, and a high-current voltage source will read the same as a current-limited [high resistance] voltage source, so a DVM won't really tell you all that much unless you have the injector connected while you take the reading.)
Airbag controllers do this all the time. They trickle a tiny current through the circuit at all times so that if there's EVER any intermittnet connection problem -be it a momentary hard-short-to-ground or a momentary open connection, it lights the airbag warning light. -that way it can be certain that when an accident occurs, the integrity of the system was always assured to be good, right up to the moment of impact.
The same method can be applied to injectors. -I cannot say for sure that it IS employed on the 944/951, but you raise a fascinating point, and the test would be very simple: -Now that the offending injector mating connection has been repaired; unplug the offending connector and try to start the car again. If it does the same "click but no start" as before, re-connect it. If it goes back to normal, we've learned that the DMU (presumably) appears to perform a potentially disabling continuity check. -That knowledge might be very valuable when diagnosing similar symptoms in the future.
I'd be most interested to see what happens if you do the test. I'm in my VW at the moment and not back with my 951 for a day or two, but if you haven't tried before then, I could try it myself. -Which injector was it, -did you already post that... -I don't recall.
Cheers!
Keith
This is supposition and conjecture, but on my '99 VW, the ECU computer checks continuously for continuity through the injectors. If it detects a fully-open or hard-short condition, it could decide not to run the motor because the motor's not in a ready condition to be run.
I really don't know how the 951 makes those decisions, but is the starter motor solenoid run straight from the key, or through the DMU? -If it's through the DMU then it's entirely possible that it -and anything else which required DMU "authorisation" could be disabled.
Basically the injectors are not unlike airbags. There's a coil which has a very low DC resistance. WHen enough current is pushed through the coil, it performs it's function, but if you 'trickle' a tiny amount of current through it at all times, you can test it's readiness. (Remember, current is different from voltage: a DVM reading the prescence of voltage is a very high-impedance device, and a high-current voltage source will read the same as a current-limited [high resistance] voltage source, so a DVM won't really tell you all that much unless you have the injector connected while you take the reading.)
Airbag controllers do this all the time. They trickle a tiny current through the circuit at all times so that if there's EVER any intermittnet connection problem -be it a momentary hard-short-to-ground or a momentary open connection, it lights the airbag warning light. -that way it can be certain that when an accident occurs, the integrity of the system was always assured to be good, right up to the moment of impact.
The same method can be applied to injectors. -I cannot say for sure that it IS employed on the 944/951, but you raise a fascinating point, and the test would be very simple: -Now that the offending injector mating connection has been repaired; unplug the offending connector and try to start the car again. If it does the same "click but no start" as before, re-connect it. If it goes back to normal, we've learned that the DMU (presumably) appears to perform a potentially disabling continuity check. -That knowledge might be very valuable when diagnosing similar symptoms in the future.
I'd be most interested to see what happens if you do the test. I'm in my VW at the moment and not back with my 951 for a day or two, but if you haven't tried before then, I could try it myself. -Which injector was it, -did you already post that... -I don't recall.
Cheers!
Keith
Injector on cylinder #2. I wonder myself if simply disconnecting the plug would create the same problem on startup. Reading through the 944 turbo factory manual, one of the tests to diagnose hard-starting issues requires that one of the injector plugs be removed: "If engine can be run, disconnect plugs on injectors seperately. If injectors are intact, engine speed will drop each time." But notice that is done on a running engine. I have not seen anything in the manual that explains what happens when an injector plug is not plugged in when attempting to start the engine.
I may try to test that tonight or tomorrow.
Regards,
Andre
06-16-2006, 08:47 PM
#10
Addict
Rennlist Member
Rennlist Member
If you have the electrical FSM, the ti signals come from DME 14 and 15 for the injectors. The ground is common and goes to the KLR...if it was up in the plug, and it made contact or the impulse jumped to ground...was the wire that was messed up the ground wire - common for all four? I'm just curious, if you traced 14 and 15 back, do they come into contact with any bus, that has a connection to 1, 18 or 35?
06-16-2006, 09:06 PM
#11
Addict
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Mar 2003
Location: South of the St-Lawrence river
Posts: 1,498
Likes: 0
Received 1 Like
on
1 Post
Originally Posted by Ski
If you have the electrical FSM, the ti signals come from DME 14 and 15 for the injectors. The ground is common and goes to the KLR...if it was up in the plug, and it made contact or the impulse jumped to ground...was the wire that was messed up the ground wire - common for all four? I'm just curious, if you traced 14 and 15 back, do they come into contact with any bus, that has a connection to 1, 18 or 35?
What is "Electrical FSM"?
06-16-2006, 10:29 PM
#13
Addict
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Mar 2003
Location: South of the St-Lawrence river
Posts: 1,498
Likes: 0
Received 1 Like
on
1 Post
Originally Posted by Ski
sorry, Elec. FSM (factory service manual) - one whole manual with schematics.
1. Bus 30 on the ignition switch is connected to battery +
2. Bus 15 on the ignition switch is connected to bus 86 on the relay G13 and bus 15 on the ignition coil.
3. Bus 50 on the ignition switch is connected to bus 50 of the starter and bus 4 on the DME computer
4. Bus 1 on the DME computer is connected to bus 1 on the ignition coil
5. Both bus 18 and 35 on the DME computer are connected to bus 87 on the DME relay.
Now I have not been able to find the inside schematics of the DME computer itself. How are bus 14 and 15 on the DME related to bus 1, 4, 18 and 35, I don't know. Maybe someone has the schematics to the DME?
Last edited by 951Porschiste; 06-16-2006 at 10:56 PM.
06-16-2006, 10:45 PM
#14
Drifting
I hate to tell you but that wire not connected to the injector did not cause your car to not start. You have to have another problem. I have been a professional mechanic for over 20 years and trained by Porsche and a loose wire on a fuel injector connector will not create a no start/no crank condition. The starter and the DME are not connected in any way. The DME can be out of the car and it will crank. You can unplug EVERY connector on the engine and it will crank.
06-16-2006, 10:55 PM
#15
Addict
Rennlist Member
Rennlist Member
Thread Starter
Join Date: Mar 2003
Location: South of the St-Lawrence river
Posts: 1,498
Likes: 0
Received 1 Like
on
1 Post
Originally Posted by Chris Prack
I hate to tell you but that wire not connected to the injector did not cause your car to not start. You have to have another problem. I have been a professional mechanic for over 20 years and trained by Porsche and a loose wire on a fuel injector connector will not create a no start/no crank condition. The starter and the DME are not connected in any way. The DME can be out of the car and it will crank. You can unplug EVERY connector on the engine and it will crank.
I'm all willing to believe you. I am not a mechanic. I'm just trying to come to grips with this no-start situation. One thing is certain, once I had that injector connector fixed the engine cranked right away. What you are saying is that I might have had another problem? How did it go away then? Maybe a better way of asking the question would be what other condition (or conditions) might prevent an engine from cranking?
Thanks in advance,
Andre