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Discussion Starter · #1 ·
1995 Saab 9000 CD (2.0 non turbo). Battery is Bosch Silver (1 month old).

I turned the ignition on (but did not turn the engine over), after a few seconds there was a small/dull bang from the engine compartment and smoke appeared from rear of bonnet. Turned off the ignition and lifted the lid to see smoke coming up from under the inlet manifold / oil filler, which soon cleared. Checked fuses - all OK. Car starts and runs OK. The ignition light is on when it should be and off when the engine is running. Voltage measurements with voltmeter across battery and readings from dashbaord display:

Ignition on: Battery 12.5 / Display 12.0

Engine idling, revving or under load (lights etc) (NB it does not make much differnce) : Battery 14.4 to 14.55 / Display between 8.7 and 11.1 (NB -once the car is running dash display stays at the same figure no matter whether revving or under load).

I suspect the voltage regulator. Can anyone confirm? And any ideas on where to get a new regulator, the alternator is Bosch 0 123 320 039.

Any advice gratefully received. Just the way to start the week :-(

Thanks / Stewart
 

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Discussion Starter · #2 ·
An update. I've taken off the alternator and the voltage regulator has not exploded. (ps. new voltage regulator was £35) I can now only assume that the bang came from petrol vapour in the exhaust - it was a VERY hot day last Sunday and I had returned from a long run the night before.

Two questions:
1. Has anyone else had experience of vapour exploding in the exhaust? Can this be caused by the cat. convertor?

2. When you start your Saab how long does it take before the dashboard voltage display shows normal voltage reading - is it instantaneous, or does it show a low voltage for a while before showing normal (12-13V)

Any advice gratefully received.

Thanks /Stewart
 

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The voltage readings that you measured at the battery indicate normal charging.

The EDU will show the lowest voltage which the battery dipped to during starting. This appears to include momentary"spikes". I've seen mine show less than 8V despite an almost new battery. The EDU shows that lowest voltage reading at every start up until you drive off then reverts to normal display (temperature on mine) after driving a few yards.

Other contributors have experienced a bang from the exhaust at start up, although it hasn't happened to me. Although in your case you didn't actually start or crank over the engine. For an explosion to occur there would need to be a source of fuel and a source of ignition. The fuel may have come from a leaky injector or perhaps the injectors spray a short pulse at igntion switch on, I don't know.
As for a possible source of ignition - the DI unit will give short a burst of sparks to clean the plugs if the car doesn't start at the first attempt. It also does this about 5 seconds after switching the ignition off. It is indeed likely that if you turn the ignition on and don't crank the starter, that after 5 seconds the DI will assume the engine has failed to start and generate a burst of sparks, thus createing the source of ignition.
I might be entirely wrong of course but this the only explanation I can think of.
 

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Discussion Starter · #4 ·
Thanks Derek

That info is really useful. It reassures me that there is no problem with the voltage regulator - so I will refit the old one and put the alternator back. I wish I had run the car for more than a few seconds at start up and driven it a few yards to see the volts display go back to normal - would have saved me a pain of a job.

Anyway - if anyone wants advice on getting the alternator off - it's a pain of a job, but reasonably well explained in Haynes. Three points to note:
1. I used a spring compressor to compress the drive belt tensioner - easier than using the Haynes described tool
2. You need a 8mm hex drive to get the alterator bolts off
3. The steering pump bracket has 4 bolts holding it onto the back of the block, which are difficult to access, but not impossible.

Thanks again Derek
/ Stewart
 

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Hi, I can understand all the explaination given so far and all seem credible. but I am puzzled about the smoke coming from the rear of the bonnet. If you had pre ignition in the exhaust this would surely show at the tailpipe not the rear of the bonnet? not trying to make problems just trying to understand it.
 

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Discussion Starter · #6 ·
Hi gelcoat.

I have (unfortunatley) an answer to the point you raise. I have a small hole in the exhaust - at the start of the concertina section - i.e. right under the inlet manifold. It had been filled with a bit of exhaust paste. Car now running fine.

/Stewart
 
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