Start question - ignition switch? relay? other?

There is no clutch sensor/neutral start switch unless somebody added one. IMO, either the battery condition is questionable or there is an issue with the ignition switch or starter relay (any of which could simply be an electrical connection issue that breaking/cleaning/remaking would correct.

NOTE: I said there is no sensor/switch but that applies to a US 328; maybe there is on other market models?

 

As Mike996 infers, check the connections - look/feel behind the ignition switch. My 328 had an intermittent ignition problem that turned out to be simply a loose connection there. Like your situation mine was a

 

I had a similar intermittent starting problem for ages. Eventually traced it to the main connector on the LHS of the fuse board - the one that runs vertically. Took all the wires & pins out the connector, cleaned them, & tweaked them up a bit. Cleaned the pins on the board & all is good Same symptoms. Turn the key & nothing from the starter but everything else obviously OK.

 

No, I think I'm talking about connector W - has a couple of big red wires into it (amongst others) which go back to the ignition switch. See Fig 6 on the wiring Diag.
That connects across the board to Relay U which is key controlled services.

 

I had the same problem but mine was the terminals on my battery where corroded and did connect only after turning the key a 3-4 times,cleaned them and no problem after,so I installed a voltage meter so with a flick of a switch I can see If I got 12+V before I turn the key.

 

The problem with the 328 starter circuit is that there are a lot of connections/joins in it & it only takes one bad one to drop the voltage sufficiently such that the starter isn't triggered when you turn the key.

Its usually not the HT circuit at all that causes an issue. Clean battery terminals will never hurt (the entire electrical system) though!

Andyww wrote a good post a while ago that detailed all the places to check & clean the connections in the starter circuit I think.

 

If I ever had this problem, not yet, I would run a couple of wires to the starter solenoid and hot wire switch under the dash and hide it there for good.

 

Another place to check is the Molex connector adjacent to the LH rear shock mount. Solenoid power goes through here and its exposed to water ingress. Late cars have a big rubber boot over it.

 

My bet is simply the main battery terminals need a clean up, there is probably some corrosion bloom around them. Second choice would be the W connector. Remove, clean using some electrical contact cleaner, ideally Deoxit, put back on. Probably a good time to Deoxit any electrical connections you can more generally, this stuff solves/prevents a lot of electrical glitches. (Lexus uses it at the factory to avoid warranty problems on the myriad of electrical devices on modern cars). http://caig.com/

 

Very much doubt its going to be the battery terminals from what you have described. If it was then you would get a click when you turned the key as the solenoid tried to engage the starter (but there was insufficient juice to spin it) . Because you are getting nothing when it fails but also that the starter is spinning properly when it works its going to be the LT circuit as above. If the voltage drops anywhere in that then it won't trip the solenoid.

Ignition switch, connector W & the Molex connector in the engine bay would be the first three (and most likely) suspects.

Of course it'll do no harm to clean the battery terminals anyway, but even if it works after doing just that I wouldn't be sure that you've cured it!

 

Spyder, the Deoxit I use is indeed the D series, I use the D100-25 which you dab a small amount from the squeeze container and work with qtips and a very small artists paint brush. The sprays would no doubt be faster, but not as economical, and I have not used them so can't say for sure. Once clean, I then use the Deoxit Sheild, which is a protective anti corrosion barrier. Again used very sparingly is the key.

Re: Iain, I once had some battery corrosion and my car was completely dead, no solenoid click, nothing. A terminal clean up was the solution, albeit I was surprised by how much corrosion bloom there was so it was kind of obvious that was something to deal with. So while I concur the problem noted might well be caused by something else, I have learned time and again to rule out the blazingly obvious things first.