Still looking for ideas on why my Exige won’t start.
I’m using a 1yr old battery with 1yr old spark plugs.
It starts fine if I used one of these in boost start mode, in fact it turns over very very fast.
If I try to start it on the battery, it turns over, but not as fast as when using the boost start thingy, and doesn’t start.
If I use jump leads with another car it won’t start, it just turns over.
Ideas?
Alternator?
I’m pretty stupid when it comes to mechanical and electrical things, isn’t the alternator employed only in the charging of the battery ?
Check plug gaps … it always helps starting if the gap is on the narrow side of spec as less energy is then needed to make the spark jump the gap …
Sounds like Government cut backs to me… perhaps your altenator has been made redundant! 
Also a lazy starter motor can compound starting problems too … particularly if it is not of the gear reduction type,although most are these days …
Low compression is the least likely … Hopefully It’s not that .
What motor is it ?
Cannot have lazy work practices now… fire that one too! 
Does it start off the battery after its been started and left running after the booster has been removed?If that makes sense.
could be alternator is not 100%working so the battery may be partially charged? therefore when you start the car it may struggle unless you use the booster?
have you got a multimeter that you can check the battery voltage with everything turned off, then check again whilst trying to start?
Yes
If that were the case then I’d still expect it to start using jump leads no ?
I’ve had the battery on trickle charge and the charger said the battery was “full”
Yep, what should I be looking for ?
I guess thinking about it, the difference between jump cables (not starting), battery (not starting) and the boost start (starting) is the ampage ? Since the manual for the boost starter says it’s still 12v but delivers up to 300amps of juice.
So I guess the battery/jump leads aren’t delivery enough amps, suggesting something along the line requires too many amps to start ?
Is there a flaw in my logic ?
[Warning: I’m no expert, but…]
I like the multi-meter idea to learn some more. I would suspect the booster is higher voltage and there is a drop/resistence between the battery and plugs which doesn’t effect the higher voltage booster. Two batteries on a jump start won’t increase the voltage, just power.
The plugs, are they the right spec? If they want a higher voltage you won’t get a good enough spark, although it may be enough once its warmed up for a restart. Sounds a slight intolerance causing a significant problem.
So what’s between/involved with the battery and plugs? Battery connector’s, some vasoline, leads to coil, coil, leads to plugs, crank sensor and ECU (I think, which I assume uses the crank sensor to instruct the coil to fire). The coil creates the 50-75,000 volts for the plugs, so I guess a drop there could effect things, and I guess the crank sensor could be involved (but I can’t quite think how).
Are all the cylinders running ok? If it was just one not firing that would cause a drag on the others.
Cheers, Ian
Thanks for the tips, it’s given me a few things to work on.
Like I said, with the booster the starter is noticeably faster, perhaps 2x faster, is that a voltage or an ampage thing (or could be both) ?
The car runs fine once started if that’s what you mean, they feel like they’re all firing.
Have you let the battery go flat at all? This can kill modern batteries. They may indicate fully charged but their capacity is vastly reduced. A few checks you can do are to check the battery voltage with the ignition off, a fully charged battery should be about 12.6v, 50% charge is about 12.2v, this will give you some indication of the state of the battery. Start the car and let it idle, check the battery voltage again, it should be between 13.5v - 14.5v, any less and the alternator output is low.
This should give you some indication on the state of your battery/alternator.
You could also get someone like quick fit etc. to carry out a capacity test of the battery, this will tell you if it’s knackered or not.
That’s a voltage thing.
Amps = longer lasting (eg. more gas in a tank)
Voltage = power (eg. Octane rating)
I’d try using a different (stand alone, not jumping) battery to start and see if that works. If not, likely something is wrong else where. Coil wld be the next place I’d look.
[quote=Dave]Have you let the battery go flat at all?
[/quote]
I may or may not have let the car stand for 6 months without charging… :whistle:
That said, I had these fun + games last year and it did the same even with a new battery.
Battery
i’d say battery too
Ok, just been and measured it
Cold 12.6 - 12.8v ( on charge all day beforehand ) - turned over, wouldn’t start
Running 13.9v
Boost starter 17v - started