993 trouble starting, sometimes...
06-07-2011, 02:07 PM
#16
I had starter issues and finally diagnosed it correctly: in my case it was the starter but I could rule out a lot by just making proper measurements:
https://rennlist.com/forums/993-foru...oot-cause.html
Just for the benefit of the great forum I want to add some details to the trouble shooting:
0. Swap DME relay with the spare I had in the glove box. Car did not give a single sound while starting -> rule out DME relay issue at the moment
1. Battery voltage 12.8 V and I switched it with the one from my second (starting) 993. Still no cranking or klicking from the solenoid -> battery ok
2. All connection at battery tight and mass band in trunk "looks like new" -> ruled out issues here at the moment
3. Switched Starter relay (R61) with a similar relay that knowingly works (e.g. horn that is easy to test). car still "dead while starting -> starter relay R61 ok
4. Pull starter relay R 61 and do the following measurements:
4.a Check pin 86 for 12V. This is the 12V from the immobilizer to the starter relay coil that acts as an interlock to start the car. In my case I got the 12 V when I opened the car properly and turned the ignition on within the required time. -> immobilizer ruled out as an issue
4.b. Check pin 85 for proper mass signal (resistance measurement against mass). MJ 97 and later have a clutch switch that provides the mass to the starter coil switch. I measured "0 Ohm" with depressed clutch -> ruled out clutch switch
The previous measurements confirmed that the starter relay coil gets the proper supply. No to the power side of R61
4.c. Check pin 30 for 12V with the ignition switch turned to position 3 (start position to crank). I measured 12 V. -> ruled out ignition switch issue
The previous measurement confirmed that the power side of the R61 gets the proper signal too (12V). This all ruled out any relay related issues "in the trunk". I than moved to the starter and its connections as I assumed that an issue with the cable that provides the switched 12 V from starter relay power side to the starter solenoid is not likely.
5. Checked starter for tight and clean connections. Need to include the mass connection at the chassis side -> everthing was thight and clean like new -> IT MUST BE THE STARTER
6. Replaced starter -> car starts as it is suppsed to start!
Bottomline is as Steve already said: Root causes can be multiple and proper and "cheap" diagnosis before replacing expensive parts like Immobilizer unit can safe both time and money.
Here is the list of potential issues again that can lead to a car not starting "from the electrical side" and I am sure there is more when you include general "cable issues" between working components.
1. DME relay
2. Battery
3. Battery connections
4. Starter Relay R61
5. Immobilizer Unit / maybe key fob if you are lucky
6. Clutch switch (for MJ 97 and 98)
7. Ignition switch
8. Connections to starter
9. starter itself
Good Luck!
https://rennlist.com/forums/993-foru...oot-cause.html
Just for the benefit of the great forum I want to add some details to the trouble shooting:
0. Swap DME relay with the spare I had in the glove box. Car did not give a single sound while starting -> rule out DME relay issue at the moment
1. Battery voltage 12.8 V and I switched it with the one from my second (starting) 993. Still no cranking or klicking from the solenoid -> battery ok
2. All connection at battery tight and mass band in trunk "looks like new" -> ruled out issues here at the moment
3. Switched Starter relay (R61) with a similar relay that knowingly works (e.g. horn that is easy to test). car still "dead while starting -> starter relay R61 ok
4. Pull starter relay R 61 and do the following measurements:
4.a Check pin 86 for 12V. This is the 12V from the immobilizer to the starter relay coil that acts as an interlock to start the car. In my case I got the 12 V when I opened the car properly and turned the ignition on within the required time. -> immobilizer ruled out as an issue
4.b. Check pin 85 for proper mass signal (resistance measurement against mass). MJ 97 and later have a clutch switch that provides the mass to the starter coil switch. I measured "0 Ohm" with depressed clutch -> ruled out clutch switch
The previous measurements confirmed that the starter relay coil gets the proper supply. No to the power side of R61
4.c. Check pin 30 for 12V with the ignition switch turned to position 3 (start position to crank). I measured 12 V. -> ruled out ignition switch issue
The previous measurement confirmed that the power side of the R61 gets the proper signal too (12V). This all ruled out any relay related issues "in the trunk". I than moved to the starter and its connections as I assumed that an issue with the cable that provides the switched 12 V from starter relay power side to the starter solenoid is not likely.
5. Checked starter for tight and clean connections. Need to include the mass connection at the chassis side -> everthing was thight and clean like new -> IT MUST BE THE STARTER
6. Replaced starter -> car starts as it is suppsed to start!
Bottomline is as Steve already said: Root causes can be multiple and proper and "cheap" diagnosis before replacing expensive parts like Immobilizer unit can safe both time and money.
Here is the list of potential issues again that can lead to a car not starting "from the electrical side" and I am sure there is more when you include general "cable issues" between working components.
1. DME relay
2. Battery
3. Battery connections
4. Starter Relay R61
5. Immobilizer Unit / maybe key fob if you are lucky
6. Clutch switch (for MJ 97 and 98)
7. Ignition switch
8. Connections to starter
9. starter itself
Good Luck!
Last edited by e9stibi; 06-07-2011 at 02:43 PM.
06-23-2011, 04:09 PM
#17
Racer
Thread Starter
Update....
Had the A/B light reset @ Prime in Norwood MA. They said that they could not diagnose the starter, since the tester they used to use for 993 was no longer operational. :-(.
A few days later, on a hot day, took it out for some errands, and smartly parked at top of a hill, nose out, and it did not start. Luckily did the old role start, got it home .. Phew... Tried to start it a few more times, same result. I then tried to jump start.. Nothing. So must be the starter.
Just spent 3 hours under the car, replaced starter.. All working nicely. It is a cool rainy day, but 'feel' that it did solve the problem. The p-car DIY is pretty good, but i don't see the need for the crazy tool at the end. There is plenty of room to work around, although you do need to do a little 'stretching' to get around the transmission.
Thanks to all for the advice.
Had the A/B light reset @ Prime in Norwood MA. They said that they could not diagnose the starter, since the tester they used to use for 993 was no longer operational. :-(.
A few days later, on a hot day, took it out for some errands, and smartly parked at top of a hill, nose out, and it did not start. Luckily did the old role start, got it home .. Phew... Tried to start it a few more times, same result. I then tried to jump start.. Nothing. So must be the starter.
Just spent 3 hours under the car, replaced starter.. All working nicely. It is a cool rainy day, but 'feel' that it did solve the problem. The p-car DIY is pretty good, but i don't see the need for the crazy tool at the end. There is plenty of room to work around, although you do need to do a little 'stretching' to get around the transmission.
Thanks to all for the advice.
06-23-2011, 05:47 PM
#19
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Location: Boston, MA
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