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Saab 9-5 2001: hard to diagnose occasional failure to start

I have a 2001 9-5 that has exhibited a problem for maybe two or three years now: It sometimes fails to start (won’t even crank) after a short drive and sitting for about an hour.

I drive to a pool almost every morning, swim for about an hour, and then drive back. It always starts fine first thing in the morning, but once in a while it won’t start after swimming. When it fails to start, if I wait about 30 minutes, it then starts fine, as if there never was a problem.

It happens maybe once every few weeks. The dealer has never been able to get it to reproduce, nor to find any fault. If I replace the battery anyway, the problem doesn’t happen again for 6-12 month. There’s never any indication that the battery is at fault (it always tests fine), but replacing it seems to help for a while.

I have a radar detector plugged in to the cigarette lighter, and it displays the voltage. When the car fails to start, the display is generally just below 12v (maybe 11.8 or 11.9). Once it starts, it’s well above 12.

I think you need a new battery. A good battery will never fall below 12VDC. Have your alternator tested as well.

Could be many things, but I agree with @Missleman and would have the charging system checked.
You say it shows well above 12 volts after starting, but what voltage. If the charging system is putting out too mush voltage, it could be boiling your battery dry.

But that shouldn’t be causing the constant problem with starting. Only when it’s been drained enough should a problem like this show up, and it wouldn’t go away in an hour.

Bad ignition switch, starter solenoid, a sticky relay, or interlock safety switch would sound more like the problem.

Next time this happens…release the key from the start position but do not turn it to off. Leave it in the on position and then check to see if the accessories (radio, heater fan) work.
That may tell us weather it is just the starter circuit or the entire electrical system that is affected. Then post the results here.

I had a Ranger years ago that I bought new. One in fifty times, when I’d turn the key to start I’d have nothing…turn the key to off and then it would start up right off as if nothing was ever a problem. I and the dealer never could track the problem down, because there the next turn of the key and all was good. It never bothered me because it was so infrequent and I was never stuck with it not starting on the second try.

Yosemite

Sounds like 2 problems or possibly 3. You don’t say whether the car won’t crank when you come out or whether it just won’t start.

#1 As @missileman says, the battery should always show over 12 volts at rest before you try and start the car. I don’t know how accurate your radar detector is at checking voltage but you should see 12.5 or better with a new battery before you start and 14.0 to 14.5 volts when running. With a new battery, seeing less than 12 volts anytime says your car is not charging the battery properly. The dealer should easily be able to check determine that so I don’t think that is the only problem. In that case the alternator may need replacing or the alternator belt tensioner may be failing. In either case the dealer should have no problem finding the issue.

#2 These cars are notorious for crankshaft position sensor failures at a bout 100,000 miles. They fail slowly. It starts exactly as you describe. Drive it somewhere, come out, the car is still a bit warm, cranks but no start. Wait a bit and the car starts fine. Just replace the sensor. It is a cheap part and easy to replace so total cost is reasonable - should be less than $200. This is a tough one for any mechanic to recreate.

#3 If it is an automatic transmission, the neutral safety switch in the shifter can sometimes wear out and cause a no start. It won’t allow the car to CRANK. If this is the condition you experience, turn the key, the dash lights come on but nothing else happens when you turn the key, that is what needs to be replaced. This is also a tough one for any mechanic to recreate.

BTW, my wife owns one of these cars - same year and model- and loves it. I must keep it running for her. Happy wife, happy life!

As I mentioned, the car does not crank at all, and the dealer was unable to find a fault in the battery, alternator, charging system, etc. I have replaced the battery three times anyway.

When the problem happens, all other systems are fine (to answer @Yosemite 's question). It just doesn’t even try to crank, nothing.

The car has under 60k miles, but possibly the neutral safety switch is starting to go, as @Mustangman says.

There may be problems with the charging system or something discharging the battery while the car sits. But I think what I’d do in this situation is measure the voltage at the starter motor, both terminals, during attempted cranking. If both measure above 10.5 volt and it doesn’t crank, I’d replace the starter motor.

Starter motors can be heat sensitive. On some vehicles there’s a heat shield to protect it from overheating. But those heat shields are often discarded by one mechanic or another during maintenance, as the get in the way. So a missing heat shield is something else to check for.

Starter.

My guess is either a faulty safety switch for transmission operation, ignition switch, or starter motor.

Starter motors are not normally a problem area on SAABs so I would lean towards the trans safety switch (varies depending upon automatic or manual) or the ignition switch which is known now and then to act up due to being located low and between the seats where dust, cookie crumbs, and spilled coffee end up…

@ok4450 SPILLED COFFEE!! Perish the thought! :wink:

SAAB thoughtfully provided an almost useless Euro-style cup holder that pops out of the dash next to the radio that really only fits the special travel mug SAAB used to sell in their accessories catalog (we have one, nothing else really fits) or a 12 oz can of soda. Europeans stubbornly don’t understand cup holders to this day.

We have a 9-5 wagon that coughed and died in rush hour traffic on my way home last fall. Would not start up again and Trader Joe’s staff (kudos to them!) rallied to push me off the 4-lane road into their parking lot. Crankshaft position sensor was replaced and no problems since.

The trouble you are having is most likely due to a faulty contact connection in the safety switch for the transmission. If you have an automatic transmission you might be able to move the shift lever around in the PARK position and make the switch work. You could also try starting the engine in the NEUTRAL position to see if that helps. If you have a manual then the switch is located at the clutch pedal.

Even though the battery voltage level you saw showed low you need to know where the power is coming from. Power to that point could be different from the starter circuit. All the circuits do tie to the battery but they take various routes to get there. Even if the battery was low the voltage you saw would at least make the starter work a little bit and the starter would show some signs of life.

I had the virtually exact same problem.Always started first thing in the morning but after a few errants in town it would no longer turn over.After cooling off for half an hour plus it would start again. Nobody was able to solve it. I removed the starter and the drive end was severely worn causing it to jam when hot. Replaced the starter and no more problems.