No hot start - solenoid?

[James]

The latest little gremlin to afflict my C900:

It's been hot lately.  100 degrees hot and more.  On a few occasions now, after a run and then being switched off for a few minutes - eg stopping to get petrol - the 900 refuses to start.  All the lights come on, the various lights go out as expected when you turn the key to 'Start', but then nothing.

Give it half an hour to cool down, and it's fine.  Or get it rolling and it'll bump-start into life no problem.

Would this be the solenoid?

[Max Headroom]

Do you hear a 'click' at all when you turn the key?

[sgould]

I used to have this happen on a Merc we had.  The problem was swarf from the starter motor commutator and brushes.  They had worn over time and the inside of the starter motor was full of greasy swarf.  I think that the heat melted the grease and the metal bits shorted things out.  When things cooled down the grease hardened a bit and the bits were insulated from each other.

Or, to put it another way.  All I did was clean out the crap from inside the starter motor.

[Audax]

When you say "nothing" do you mean turn the key and nothing at all happens (started doesn't spin) or does it turn over and not fire? I'm not sure the exact sequence of how and why they fail or what happens on a c900 but I've been told crank sensor failure isn't uncommon on them.

[Max Headroom]

I used to get the exact same symptoms on my MG in very hot weather - it was a known problemhowever, and was caused by fuel evaporation. Just like you, a short stop to fill up etc and I could never relight the engine. Luckily I knew someone at Benetton F1 and he got me some kind of spaceage heatshielding that kept the heat from the exhaust manifold away from the carbs and it pretty-much cured the problem

[James]

To clarify:  When this happens it doesn't turn over, there's no click - nothing beyond the expected warning lights going out. 

[sgould]

I believe that all the lights go out because of the way the ignition switch is wired, not through current draw through the starter solenoid.  So if there is no click at all, it would seem to be a problem with the ignition switch or an ignition relay"

[DRM]

Is your car automatic or manual transmission?

[James]

It's manual, although it was originally an auto so I guess we can't discount the possibility of some sort of wiring issue ...

[DRM]

Check the neutral safety switch is not still wired in somehow.  When mine was playing up I had the symptoms you described.  Usually to be found on top of the transmission, beneath the battery case.  I hope that they removed it when the manual conversion was done.

I am intrigued that you have changed it.  It is something I frequently contemplate, but while the auto box is good I will keep going.  It is the best automatic car I have driven, but nothing betters a manual.

[James]

Here's another piece of evidence:

I generally drive with the lights on.  Sometimes if it's hot and the car won't start, I turn the lights off (thus eliminating a reasonably large current draw) and it starts.

Anyway, it's booked into the local Saab tech on Saturday to have this looked at - more as and when.

[chris aka zaphod]

I had this exact issue, your symptoms, and diagnosis on my first 9000. My initial thoughts was dirty connectors to the battery - does one terminal get warm when you try to start - and/or an earth issue.

Turned out that it was the battery, and a manufacturing fault.

HTH

[supremedalek]

I too would check the battery, but also the starter and wiring. You see, I have the odd habit of replacing the main positive (battery to starter to alternator) and negative (battery to, well, you know. Also the big transmission to ground) wires with 4Ga welding cable and copper ends. But, I have seen the starter solenoid wire (the one from the ignition key) go bad in other cars *and* the solenoid itself take a dump.

[James]

I have to say I feel like a bit of a twonk - this one was diagnosed as a loose connection at the positive terminal ...