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Discussion Starter · #1 ·
My lovely J reg Saab 900 dies fairly randomly, but usually when warmed up having been driven for 20-30 mins. Usually when going slowly in a low gear (though it's an Auto). Replaced coil, ignition module, distributer cap. The ignition module made a difference as it wouldn't restart when it failed but now it will restart. The annoying thing is it might happen once on a 40-mile journey and when have taken to a couple of different mechanics it doesn't fail on them. The last couple of winters it has been difficult to start from cold where previously it always started first time and never failed. Any ideas of any checks appreciated.
 

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My '87 Conv Turbo is doing the same thing. The two main relays and fuel pumps have already been replaced in mine. I think we will swap the ECU with a spare unit and see if that helps. I always have spark but no fuel.
 

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Discussion Starter · #3 ·
My '87 Conv Turbo is doing he same thing. The two main relays and fuel pumps have already been replaced in mine. I think we will swap the ECU with a spare unit and see if that helps. I always have spark but no fuel.
Brilliant, v helpful and the ECU a good idea. If you get sorted let me know and I'll post here too if/when sorted.
 

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My lovely J reg Saab 900 dies fairly randomly, but usually when warmed up having been driven for 20-30 mins. Usually when going slowly in a low gear (though it's an Auto). Replaced coil, ignition module, distributer cap. The ignition module made a difference as it wouldn't restart when it failed but now it will restart. The annoying thing is it might happen once on a 40-mile journey and when have taken to a couple of different mechanics it doesn't fail on them. The last couple of winters it has been difficult to start from cold where previously it always started first time and never failed. Any ideas of any checks appreciated.
Just curious... When was the last time the fuel filter was changed? Are you sure that the issue is related to the ignition/electrical system?
 

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Discussion Starter · #5 ·
Just curious... When was the last time the fuel filter was changed? Are you sure that the issue is related to the ignition/electrical system?
Yes, that was one of the first things we thought of and seems to be fine. There was no spark from the (new) ignition coil. At the moment, as it's a non-turbo, we're now thinking it's the crank shaft position sensor. These seem hard to find (and expensive) to replace unfortunately.
 

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My lovely J reg Saab 900 dies fairly randomly, but usually when warmed up having been driven for 20-30 mins. Usually when going slowly in a low gear (though it's an Auto). Replaced coil, ignition module, distributer cap. The ignition module made a difference as it wouldn't restart when it failed but now it will restart. The annoying thing is it might happen once on a 40-mile journey and when have taken to a couple of different mechanics it doesn't fail on them. The last couple of winters it has been difficult to start from cold where previously it always started first time and never failed. Any ideas of any checks appreciated.
There are several system components that can cause your issue as you described. 1st check , check the Crankshaft sensor, when going bad they tend to malfunction after getting warmed. I would check the resistance across the Crankshaft sensor wires, preferably while sensor is out of engine block. Also, on a tear bench you can hear the Crankshaft sensor with a hairdryer and monitor its resistance values with Ohm meter.
Also, during a no start condition, check the fuel pressure on fuel rail while cranking, check the specs and make sure it's within tolerance. bottom line, you need Spark, fuel and compression for engine to start. I would also check the Ignition voltages controlling the spark p,up to fire.
 

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My lovely J reg Saab 900 dies fairly randomly, but usually when warmed up having been driven for 20-30 mins. Usually when going slowly in a low gear (though it's an Auto). Replaced coil, ignition module, distributer cap. The ignition module made a difference as it wouldn't restart when it failed but now it will restart. The annoying thing is it might happen once on a 40-mile journey and when have taken to a couple of different mechanics it doesn't fail on them. The last couple of winters it has been difficult to start from cold where previously it always started first time and never failed. Any ideas of any checks appreciated.
What year? Turbo or 2.1L? When it conks out spark or no spark? If no spark then my mind goes directly to the always popular crankshaft position sensor - which on a turbo is a minor nuisance to replace and on a non-turbo 2.1 is a major league pain in the balls.
 

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Discussion Starter · #8 ·
What year? Turbo or 2.1L? When it conks out spark or no spark? If no spark then my mind goes directly to the always popular crankshaft position sensor - which on a turbo is a minor nuisance to replace and on a non-turbo 2.1 is a major league pain in the balls.
Thanks Phil. Drove it from Todmorden, West Yorkshire, UK to the Isle of North Uist in Scotland with three ferries in between last week. About 1000 miles, purring like a Swedish cat. All done thanks to replacing the crankshaft position sensor. It is non-turbo, so you're right, finding it was a bit of a task. And finding a replacement at a reasonable price (in EU) was also a fair job. Feels like having a brand new car. Very happy.
 

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I finally think we got to the bottom of my random stalling and starting issue. After stalling along the road and not starting we were able to diagnose the issue. We found a loose connection on on of the wires that came from the over boost switch. I measured voltage on both sides of the boost switch and the relay wasn’t activating. Crazy.
 

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Thanks Phil. Drove it from Todmorden, West Yorkshire, UK to the Isle of North Uist in Scotland with three ferries in between last week. About 1000 miles, purring like a Swedish cat. All done thanks to replacing the crankshaft position sensor. It is non-turbo, so you're right, finding it was a bit of a task. And finding a replacement at a reasonable price (in EU) was also a fair job. Feels like having a brand new car. Very happy.
Right on! I just replaced one on a 92 vert last week - not a fun job, the wounds are still fresh! ;). Glad you got it all squared away!
 
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