Carrera 3.2 no-start big mystery - Page 2

JCF · 10-28-2009, 08:46 AM

When the engine dies, I still have ignition.
I tryed swapping the coil with a new one, and I said in my first post, tested the fuel pressure in the ramp (with a BOSCH gauge, accurate).
When the engine stops, it stops almost as a ignition cut (not long stall then die...) ; but when checking, still have ignition and injection...
The DME relay "knock" after the engine stops, so the system is still powered.
Mad thing.

theiceman · 10-28-2009, 10:02 AM

you gad pressure when it ran ... how about when it didn't ?

JCF · 10-28-2009, 10:29 AM

No problem when the car doesn't run : the pressure go down (about 2.2 bar) when cranking and firing (because of the vacuum) and when the engine dies et stops, hold 2,5 bar.
And the pressure grows quickly just after I connect the gauge (even when my problem occurs) so the pump does its job...

JCF · 10-28-2009, 04:04 PM

Today, I let the Motronic opened (very carefully) to try to find a overheating component. I started the car and let it warm. After several time, never cut. I try to "shake" the DME relay and I can sometimes have a engine stop, but it's not the same problem because I can hear and feel the switch by the coil in the relay (moreover, I tried to shunt the relay and when the problem occured, it didn't change anything). Remove the cap on the relay plug to see if wires could be bad soldered or cut, nothing. I will all the same buy a new relay.
Today, I think I let the car running (at idle with some throttle moves) during between 30 and 60 minutes, and it never fail. 10-15 minutes makes it cutting before. Very very strange behaviour which doesn't help me to solve this problem...

rusnak · 10-28-2009, 05:48 PM

+1 on Iceman's post #17. I'd keep the gauges on there, as well as a spark tester. When it stops, (not while it is running), before turning off the key, did you check to see if you have 12v input power to the ignition coil (terminal #15)? It is powered from the key, not the DME module. If not, then you may have a bad ignition switch. I just re-read some notes that I took, and no power to terminal #15 was thought to be due to a bad ground in a previous thread this year on Rennlist.

JCF · 10-28-2009, 06:36 PM

Quote:

Originally Posted by rusnak

+1 on Iceman's post #17. I'd keep the gauges on there, as well as a spark tester.

I think I have some difficulties with English and I apologize about that. This test was done and all was fine.

Quote:

Originally Posted by rusnak

+When it stops, (not while it is running), before turning off the key, did you check to see if you have 12v input power to the ignition coil (terminal #15)? It is powered from the key, not the DME module. If not, then you may have a bad ignition switch. I just re-read some notes that I took, and no power to terminal #15 was thought to be due to a bad ground in a previous thread this year on Rennlist.

It's a very interesting thing and I will check this as soon as possible (or as soon the problem comes back). On my wiring diagram, the 12v at the coil is provided at the fuse box and powers also the DME relay (which is still powered during the problem), so I thought that if the DME was powered, except cut wire, the coil should be powered.
But.... after 86 the diagram changes as an anti-theft powers the relay. In my case, there's not anti-theft... but maybe was it removed. Moreover, I had spark during the problem, but you're absolutely right that I've to check this.
Hope I can do it tomorrow and will let you know...
Thanks for giving me your time.

JCF · 10-29-2009, 04:15 PM

No problem today, tested again a long time... The engine never stopped. I did nothing that change the configuration. Will try a road test tomorrow if possible.

JCF · 10-30-2009, 06:07 PM

I understand nothing. Today was a good weather day so I can test the car ; and as yesterday and 2 days ago, it runs perfectly. I don't understand. One week ago, the engines systematically died after 10/15 minutes and after, the starting was erratic. Before and today, there was no problem. Not once. And I don't really know why, I just made some solder at the DME relay connector but I don't think they could lead to this kind of problem (and the old ones were not bad).
Hope never have this problem anymore. In all case, I've new sensors, which is not a bad thing knowing how look the old ones, and I've fix a possible ignition problem because of the cold solder in the DME...

To be continued... maybe.

Jascha-M · 11-01-2009, 09:44 AM

I am a little late to offer much for the 'Suggestion Box'... the symptoms you described at the start of this posting are characteristic of a bad head temperature sensor that has a 'high' resistance value (k-ohm) when cold but quickly changes to 'low' resistance (ohms) when engine warms up... The miraculous recovery is not not consistant with this common problem.

Hope it lasts...!

JCF · 11-01-2009, 12:19 PM

Quote:

Originally Posted by Jascha-M

I am a little late to offer much for the 'Suggestion Box'... the symptoms you described at the start of this posting are characteristic of a bad head temperature sensor that has a 'high' resistance value (k-ohm) when cold but quickly changes to 'low' resistance (ohms) when engine warms up... The miraculous recovery is not not consistant with this common problem.

Hope it lasts...!

No problem with the "little late", any proposition is well appreciated !

But unfortunately, I controlled the head sensor and it never give me a short / open or a bad value. Controled both in the engine compartment and at the pins of the Motronic. Moreover, when the problem occurs, disconnecting the temperature sensor makes the engine runnning... instead of dying (dying which occurs when disconnecting the sensor when the engine works fine). That's why I think about an over-lean mixture, countered by the over-rich mixture of the open-circuit at the sensor when removing. And as I said, no problem since a few days...

10-28-2009, 05:48 PM	#20
rusnak Addict Rennlist Member Join Date: Nov 2008 Location: Fresno, CA Posts: 5,086	+1 on Iceman's post #17. I'd keep the gauges on there, as well as a spark tester. When it stops, (not while it is running), before turning off the key, did you check to see if you have 12v input power to the ignition coil (terminal #15)? It is powered from the key, not the DME module. If not, then you may have a bad ignition switch. I just re-read some notes that I took, and no power to terminal #15 was thought to be due to a bad ground in a previous thread this year on Rennlist. __________________ I run from earth-crossing asteroids...or from cross, earthy women on steroids. Last edited by rusnak; 10-28-2009 at 06:03 PM.

11-01-2009, 09:44 AM	#24
Jascha-M Addict Rennlist Lifetime Member Join Date: Jun 2001 Location: Pennsylvania Posts: 139	I am a little late to offer much for the 'Suggestion Box'... the symptoms you described at the start of this posting are characteristic of a bad head temperature sensor that has a 'high' resistance value (k-ohm) when cold but quickly changes to 'low' resistance (ohms) when engine warms up... The miraculous recovery is not not consistant with this common problem. Hope it lasts...! __________________ Jascha '96 993 (SOLD) '89 911 (Perfecting) ! Support Rennlist by Becoming a Member Today ! Last edited by Jascha-M; 11-01-2009 at 11:49 AM.

10-28-2009, 08:46 AM	#16
JCF User Join Date: Feb 2004 Location: France Posts: 50	When the engine dies, I still have ignition. I tryed swapping the coil with a new one, and I said in my first post, tested the fuel pressure in the ramp (with a BOSCH gauge, accurate). When the engine stops, it stops almost as a ignition cut (not long stall then die...) ; but when checking, still have ignition and injection... The DME relay "knock" after the engine stops, so the system is still powered. Mad thing.

10-28-2009, 10:02 AM	#17
theiceman Addict Rennlist Member Join Date: Aug 2005 Location: Cambridge Ontario Posts: 9,897	you gad pressure when it ran ... how about when it didn't ? __________________ 78 SC Targa 76 XS360 95 Audi 90 Sport 09 Maxima Gone but not forgotten 87 944S " I'm not very smart but I know how to google "

10-28-2009, 10:29 AM	#18
JCF User Join Date: Feb 2004 Location: France Posts: 50	No problem when the car doesn't run : the pressure go down (about 2.2 bar) when cranking and firing (because of the vacuum) and when the engine dies et stops, hold 2,5 bar. And the pressure grows quickly just after I connect the gauge (even when my problem occurs) so the pump does its job...

10-28-2009, 04:04 PM	#19
JCF User Join Date: Feb 2004 Location: France Posts: 50	Today, I let the Motronic opened (very carefully) to try to find a overheating component. I started the car and let it warm. After several time, never cut. I try to "shake" the DME relay and I can sometimes have a engine stop, but it's not the same problem because I can hear and feel the switch by the coil in the relay (moreover, I tried to shunt the relay and when the problem occured, it didn't change anything). Remove the cap on the relay plug to see if wires could be bad soldered or cut, nothing. I will all the same buy a new relay. Today, I think I let the car running (at idle with some throttle moves) during between 30 and 60 minutes, and it never fail. 10-15 minutes makes it cutting before. Very very strange behaviour which doesn't help me to solve this problem...

10-29-2009, 04:15 PM	#22
JCF User Join Date: Feb 2004 Location: France Posts: 50	No problem today, tested again a long time... The engine never stopped. I did nothing that change the configuration. Will try a road test tomorrow if possible.

10-30-2009, 06:07 PM	#23
JCF User Join Date: Feb 2004 Location: France Posts: 50	I understand nothing. Today was a good weather day so I can test the car ; and as yesterday and 2 days ago, it runs perfectly. I don't understand. One week ago, the engines systematically died after 10/15 minutes and after, the starting was erratic. Before and today, there was no problem. Not once. And I don't really know why, I just made some solder at the DME relay connector but I don't think they could lead to this kind of problem (and the old ones were not bad). Hope never have this problem anymore. In all case, I've new sensors, which is not a bad thing knowing how look the old ones, and I've fix a possible ignition problem because of the cold solder in the DME... To be continued... maybe.