S3 – mystery failure to start

[tileart]

After a largely trouble-free year’s TVR’ing in my S3, today I had one of those “I really wish this hadn’t happened” moments, the only good part being I had just got back home from a thoroughly delightful blast in the countryside this superb hot evening. When going to put the car back in the garage, I turned the key but the engine failed to start. Everything went dead -- it did one of those “click – dead” things that usually means the battery has died. The battery is just over 2 years old and under 4,000 miles, with a lot of short journeys. As nothing electrical was working, I retrieved my jump leads from the S3 boot using the “secret access” route, and successfully jump started the car using the battery in the Daily Drive. I checked the S3 battery and it reads 12v but (because of the space and access) I can’t get a meter onto it when it’s running. I had a similar incident a couple of weeks back when I stopped to re-fuel, but after waiting five mins or so it started OK.

So before I go to check/buy an expensive new battery tomorrow morning, any suggestions as to the Top Three likely causes ?
1. Dead battery ? (and if it is indeed this, then I also need to know why)
2. Some kind of weird thermal cutout that I didn’t know existed ?
3. Dodgy fuse somewhere ? (I pulled out the fuse box but there’s no sign of anything blown).

Thanks for any thoughts.

[phillpot]

fuse unlikely, blown fuses don't come back to life.

Batteries can and do fail even within Warranty period.

No mystery thermal cut out apart from all the wiring between the battery, ignition switch and starter getting hot and tired, particularly the infamous "yellow connector"?

[GreenV8S]

There are several faults that can cause the 'dead starter motor' symptoms. Any of them can be heat related and cause intermittent starting problems:

• battery voltaqe low
• excessive voltage drop in the solenoid activation circuit from the battery positive, through the ignition switch and alarm/immobiliser to the starter motor solenoid (the dreaded yellow connector is a common point of failure)
• starter motor mechanically sticking due to heat, dirt and corrosion

You may have one or more of these problems. Best to check for all of them and correct any you find.

If you are stranded and have nothing else to lose you may find that just holding the key in the 'cranking' position may eventually result in the starter motor kicking into life after a long delay, especially if you get somebody to tap the body of the starter motor with a piece of wood to encourage it.

[996Keef]

Engine earth strap would be my first check. Jump lead between engine block and chassis should rule it out

[tileart]

Post mortem:

Not the battery (it showed a healthy and sustained 12.86 volts on test at my local car spares / battery place.
Not the earth straps/cables, I checked the earths with an ohmmeter, and to be sure I cleaned and no-corroded the cable ends.
And noted that fuses do not self-heal.....

Which is all a bit annoying as that means I may have a dodgy starter or the dreaded yellow connector syndrome.

I'll wait until tomorrow's forecast "Furnace Friday" then take her out for a blast, being sure to take easily-accessible jump leads, a selection of the right-sized spanners, and the targa panels just in case !

[GreenV8S]

In preparation, you could securely attach a flying lead to the starter solenoid control terminal so that you can measure the voltage at the solenoid if it does again. (Obviously you would also need a voltmeter with you and a means to connect it to battery -ve to do this.)