Cuts out when hot! Help majorly needed.

[DaneC]

Major BUMPage, need some help with this one guys!

The car has stopped working on three occasions for me now - all in the last 2 weeks.

1. First time was that it would not start after I had parked it in an underground car park - had no spark so was AA'ed home. Didn't try starting it until the morning after, started straight away as if there was nothing wrong with it - I had taken the crank sensor off and cleaned it prior to starting it again, so I assumed I needed new crank sensor. However I didn't get a new one straight away as it was now fine.

2. Parked in a different underground car park this time, exactly 1 week later, same story - drove in fine, wouldn't start again 3 hours later. Tried taking the crank sensor off and cleaning it but didn't do anything - then it just started as normal an hour later.

3. Changed the crank sensor now for a brand new one and parked in the original car park where it all went wrong and it was fine, but then 1 week later I had been in heavy, slow moving traffic for about 30 minutes and the car cut out on me, and wouldn't start again. When I first tried to start it it sounded like it was trying to start but couldn't make it, then it just didn't bother trying and just span the engine round. Let the car cool down until the water temp needle is right on the bottom and it started just like that. I then drove it into another underground car park where it died on me again as I was parking. This time I had to wait 45 min after the needle hit the bottom and it started as if nothing was wrong.

When it doesn't start, the rev counter doesn't move suggesting crank sensor fault, however you can smell petrol and I was under the impression that the injectors need the crank sensor to work?

It looks like it is heat related, and my header tank cap seal had broken (which I have no replaced), would this cause any problems like this? Can't see it personally, the water temp needle never went above 3/4, and the fan works fine.

Thanks for reading!

[kenny]

If it's happened 3 times in 2 weeks does that mean you don't use it often and it happens nearly every time out, or, it's a daily drive so it's an intermitant, occaisional fault? the time and locations might be coincidental if in regular use. I had the same fault some years ago with a renault 25, the cause was a dodgy rotor arm, spark was tracking away from distributor cap terminals, sometimes it would start, sometimes not, other times it would just stop then somtime later start again. check rotor, cap and HT connections. Easiest place to start.

[DaneC]

I use it every day, but has cut out every time/after every time I had driven it in heavy, slow traffic. Cap and HT leads are fine, will check the rotor arm.

Cheers dude.

[Wobba]

Dizzy, spark plugs, wiring shorting out somewhere, or bad earthing.

[Purple]

Is the fuel pump priming when you turn the key to accesory position? If it's not, check the fuel pump electrics.

[DaneC]

Fuel pump primes, and you can smell fuel when trying to start it.

[Evogone]

TPS switch shorting out and reading full throttle wont start as its flooded and too much fuel. Same could be with the CTS shorting and giving cold reading when hot so too much fuel so wont start when hot.....

[DaneC]

And again today, took 5 minutes to get it going again. Just completely randomly cuts out when at low revs, tries to start a few times but sounds like only 1 or 2 cylinders are firing and has movement on the rev counter, then just turns over with no movement on the rev counter. After 5 minutes it started sounding like it was on 1 or 2 cylinders again, and then just started up as normal and was fine after.

Only been driving it for 5 minutes too so was only just warm.

[Wobba]

Well, I reckon it's bad earths or bad wiring!

[DaneC]

Guy on C16V had a similar problem and his turned out to be a coolant blockage - is there any built in protection system to stop the engine starting if there's a cooling issue?

[Wobba]

Guy on C16V had a similar problem and his turned out to be a coolant blockage - is there any built in protection system to stop the engine starting if there's a cooling issue?

No.

The only thing this would cause is overheating and then the subsequent failure of other things like head gasket.

[Wobba]

You could try a spare ECU. It's unlikely but it could be an intermittent ECU failure.

Also check the little hose pipes from the MAP sensor, make sure there is no blockage or leak.

[Purple]

Well, I reckon it's bad earths or bad wiring!
Quick way to check/remedy this problem is to run some cheap, thick copper wires from the battery negative to chassis points near to most of the major electrical components (eg: alternator, ECU etc).

[DaneC]

Air lock in coolant system causing ECU to think its cold when it isn't, causing fifth injector to flood engine even when driving? Possible? Can't see any wiring problems.

[DaneC]

Well something is causing the car to flood all cylinders, so the ****er is disconnected for now!

[Wobba]

Air lock in coolant system causing ECU to think its cold when it isn't, causing fifth injector to flood engine even when driving? Possible? Can't see any wiring problems.

I don't know if that's possible but there would be no harm in a major coolant system flush, and new CTS sensor, only a tenner from GSF.

Have you tried bleeding the coolant from the radiator bleed point?

Have you checked condition of ECU and vacuum pipes?

If it is the cold start injector I imagine it would be a surefire way of testing to see if it was that by unplugging the power to it? Not sure what effect that will have.

[DaneC]

For anyone that is interested, the problem appears to have gone away now, although I'm not 100% sure on what caused it. I cleaned up some corrosion from the ECU (it got wet) and cleaned earths, although none of them appeared dirty.

Wobba, you were right though!

[Wobba]

Hehe, it pulled the old ECU trick on ya eh? They do that when they want attention, crafty little beggars these Williamses!