Car wont start when temp drops
 

I've placed this issue in another thread but i was thinking it was getting lost at the bottom, so I thought I'd start a new one. The issue is it will only start if the temp is above -8c. Sounds funny, but if I leave it in the garage over night or for a week, it will start no problem. If I leave it outside and the temp drops below -8c then no crank. I still have plenty of power but nothing happens. If I keep turning the key eventually it will start, Its never stranded me somewhere, but it may take a 100 turns and it will finally turn over. The battery and starter are both only a year old and the car has never been flooded. When it does crank, it turns over no problem.
I cleaned all the connections and I ran a wire from the "s" terminal on the starter to under the hood. The idea being that when it doesn't start I can see if I'm getting the "start" signal to the starter. So I tried it out today, no crank, check for power at my "s" terminal, NONE. So my starter is not getting the signal when its cold. My question is; Which relay is the starter relay, none of them are labeled as that, the closest is labeled "IGN" but I don't think that is it it. I have all the wiring diagrams but not the locations in the PDM. Any help would be appreciated.

also i've bypassed the starter interrupt switch so it doesn't interfere with rest of my diagnostics, so consider it eliminated.

Edit: Re-read your post and it looks like it could be a bad connection instead, I've seen temps be a bugger in these situations.

There is no 'starter relay.' As in most vehicles, it's direct-powered to preclude just such a potential power interruption.

Cold oil can cause 'hard starts' due to increased friction and as many you may want to go with a lighter weight oil in the Winter.

Although your battery is only a year old it would be a good idea to have its capacity checked (not just its instantaneous voltage). You may also want to get a higher cold cranking amps (CCA) rated battery.

Is your one year old starter the upgraded (faster cranking) model?

Are your sparkplugs and 'plug cables in good order?

Cold weather starts are the most system-taxing and a good end-to-end ignition system is a necessity, along with the proper fluids for the operating environment.

I guess I should of added this but I knew it wasn't the cause of my issue. I tested the battery at 150amps for 15 secs and the voltage only dropped to 11.02v so that battery is fine. A low battery wouldn't explain no power to the starter 's' terminal, also with a charged battery or even a battery at 75%, oil would not prevent the engine from turning at all, same goes for plugs and wires.

Its a good point to keep your cars fluids at the appropriate weight for there environment but I don't think that is causing my problems. The car has started, even with these problems, in -30c weather. It turned fast and fired right up. The starter is the upgraded one as well.

There is a relay according to the mazda wiring diagrams and that makes sense, because the ignitions switch as well as the interrupter switch would have to be unrealistically large to handle the current needed to activate the pull-in windings in the starter.

I'm looking for that relay because its the next component in the power flow. If I am not getting power to the s terminal when its cold, then I want to trace back to the next component or connections to find where the power is stopping. That way I can eliminate or condemn components as I go. Like I said, if I keep turning the key the car will start as though there is no problem at all, it never starts slow and it always fires right up, there is just a intermittent no power situation.

Intermittents are truly the most difficult to troubleshoot. Everything else being equal, which apparently they are, it would appear that a connection is opening through contraction when very cold. All the best.

Yes they are. A least I can reproduce the problem, its just time consuming waiting for the car to cool down. Thanks for the help.

You sure it is a relay and not the solenoid you're looking for? There is also a fuse under the hood you need to worry about which might flake out here and there I guess.

The solenoid is on the starter, and the "s" in "s" terminal is for solenoid.

I just found the and confirmed the relay. I found it in a parts manual label as the starter lock-out relay, on the car its labeled "ST". So I've installed yet another wire on the relay so I can see if I'm getting power to the relay. Now time for some more cold weather testing, to bad the temp is going above zero!