Zafira problem

[#1]

The recent driving query thread prompted me to post details about what happened with my 13 reg Zafira last Thursday.
I stopped at a roundabout and it stalled... wasn't anything I had done and it took an age to restart (well, with a row of cars behind, 20 seconds seems like a age) then suddenly it sprung to life and I drive on dismissing it as a blip. Later on in the evening I had parked up for a while for a spot of moonlight walking but when I tried to start it it simply wouldn't . It wasn't the battery as it was definitely 'ticking over' and I had about 30 miles of petrol left. Just in case it was a battery issue (pretty sure it wasn't) I turned everything off for around 20 minutes. Still no joy.
Decided that I'd better call the RAC only to find that I had no mobile, data or satellite signal at all. So, there I was in the middle of nowhere with a car that won't start and no way of contacting anyone. Eventually a lone car came along which I flagged down and was a very kindly cab driver who took me to the nearest village where I could get a signal and phone for help. He then took me back to my car all for no charge.
When the RAC guy arrived he couldn't get it to start and mentioned that it seemed that no petrol was getting through. He attached his tablet thingy which constantly indicated 'No fault found'. So he set about putting it on his tow-truck. Just before using the winch he decided to lock/unlock the door and try again and, lo and behold, it started. Yet I had locked/unlocked it earlier when I went to the village to make the call.
Anyway, he still took me to the garage I bought it from which was some 40 miles away just in case the same happened again. Spoke to the dealer (genuine Vauxhaul franchise)  the next next morning (slept in the car) who said that their equipment would give no more info than the RAC's so, unless it happened again while there not much they could do.
It hasn't happened since. It is due it's 3rd service and 1st MOT on the 22nd so maybe something will come to light then otherwise I am stumped.
Anyone got any ideas?

[#2]

May not be relevant, but I had similar intermittent fault on my old Skoda...  I suspected the ignition switch, because of the age of the car, ( almost 12 yrs old at the time).. and figured that the switch contacts could well be worn after so much use.. also there could have been wear and tear on the barrel causing the contacts to "mis-align" occasionally.  So, I contacted my tame mechanic, and bought a replacement switch, which he fitted, ( took about an hour ).. drove down the road the next day to the shops, and when I came out, it would not start , after a few more turns of the key, it did start !...
called back my tame mech again, and he scanned around the wiring under the bonnet, and found a thin ( presumably low current 12V) wire with at dodgy connection... he bared the wire and twisted it on to the terminal, as a temp measure, and the fault never appeared again...
... so check out the low current 12v wiring to the starter solenoid...

[#3]

Quote from: Mav

Anyone got any ideas?

Too much computer control over the car...

[#4]

Maybe it's worth doing the usual computer turn off and back on again which does seem to clear up things sometimes.
Just disconnect the battery for half an hour.

[#5]

Couldn't they supply a CTRL+ALT+DLT key?

[#6]

Not Zafir as I know

[#7]

Any software updates available?
Vauxhall dealer should have checked while they had it.

[#8]

Petrol or diesel?
Edit: An afterthought! This might be a fuel tank venting problem. If the tank is under a slight vacuum when you stop, the fuel pump will not have enough umph (because the engine demand is very light and the pump is running at low speed) to pull fuel into the injectors. So you lose the engine. Tends not to happen at speed because the fuel pump will have enough umph to pull fuel through (unless the vent pipe is totally blocked).
Used to happen a lot with carburetted engines. The engine will always restart after a while because the vacuum has gradually dissipated and everything seems back to normal until next time.
If and when it happens again, nip out and remove the fuel tank filler cap. If you hear a hiss as it comes off then that's the problem. The solution is to locate the vent pipe and remove whatever is blocking it. Otherwise back to square one!  

[#9]

Many modern cars have an inertial fuel shut-off (designed to shut off the fuel supply in the event of an accident), sometimes these can 'partially trip' causing intermittent fuel supply issues - might be worth having that checked.

[#10]

Quote from: nozzer

If and when it happens again, nip out and remove the fuel tank filler cap. If you hear a hiss as it comes off then that's the problem. The solution is to locate the vent pipe and remove whatever is blocking it. Otherwise back to square one!

Strange, but I seem to remember always hearing a hissing sound emanating as I remove the filler cap.
I even remember this happening on my old Primera every time the filler cap was removed. Not saying you are wrong, just wondering why I haven't had this issue before?

[#11]

What's a vent pipe?
The petrol goes in and apparently disappears...

[#12]

It certainly sounds like a fueling problem. The thing is, unless you've got the mechanical aptitude, tracking down the cause yourself will be difficult given the intermittent nature.
Can you elaborate on how the RAC guy concluded that it 'seemed no petrol was getting through'? Whilst the pump might be submerged in the tank (and, incidentally, usually runs at a constant speed regardless of engine speed) there is usually a check connector in the engine bay to enable you to confirm whether power is being applied to the pump. Confirming that there is rules out a number of potential causes from further analysis. If the pump is receiving power (for a short 'priming' period at ignition switch on then continuously from then on) then the next step would be to measure the pressure at the fuel rail - this would confirm whether the pump was actually working properly.
Again though it'll be difficult to track down the cause without this sort of 'live' fault finding. Your best hope will be that the problem either gets better or worse - if the former then forget about it, if the latter then it'll be easier to pinpoint what the problem is. Whilst there is a lot of complexity to the operation of an engine as a whole if you break the system down into its component parts and functions you can soon narrow down where the problem likely lies.

[#13]

Quote from: Mav

Quote from: nozzer If and when it happens again, nip out and remove the fuel tank filler cap. If you hear a hiss as it comes off then that's the problem. The solution is to locate the vent pipe and remove whatever is blocking it. Otherwise back to square one!   Strange, but I seem to remember always hearing a hissing sound emanating as I remove the filler cap. I even remember this happening on my old Primera every time the filler cap was removed. Not saying you are wrong, just wondering why I haven't had this issue before?

The acid test is if it restarts after taking off the filler cap then it's vacuum in the tank.