310S Ignition failure at 70 mph in heavy rain

[Peter_Bullen]

Unfortunately I was driving along the A505 dual carriageway in my 310S (Sigma engine) in yesterday's heavy rain at 70 mph on my way back to London when the ignition suddenly died and the immobiliser came on.  All rather scary. Dead car now back home with no ignition and the speedometer stuck at 70 mph. I have checked fuses and the speed sensor. All OK. has this happened to anyone and any ideas what to check next.? 

[Alan Reeves]

Have you checked the fuse that links to the speed sensor. Mates had several fuses blown due tge sensor, needs to disconnected before a new fuse is out in 

alan

[Jonathan Kay]

What Alan says, discussed in these threads.

What other circuits are still working? Other instruments, lights, horn, wipers etc.

What's the battery voltage?

Does the red charging warning light come on with the key?

Have you got the layout diagram for your fuses and the appropriate wiring diagram? If not let me know if you'd like a copy.

Jonathan

 

 

[Jim 123]

When you switch on what happens with the immobiliser light, flashing or does it extinguish? 

[Jim 123]

When you switch on what happens with the immobiliser light, rapid flashing or does it extinguish? 

[Peter_Bullen]

Hi Jim Thanks for the reply. The immobiliser light just stays flashing in normal immobilise mode. No fuses blown. I'm wondering about the sped sensor. I disconnected it but nothing changed. The odd thing is that the speedometer is stuck on 70 mph. Thanks for your help.

 

[Peter_Bullen]

Thanks for the reply. lights, instrument lights and horn all working. Nothing else except the immobiliser. I need to borrow a multimeter for battery voltage. Nothing changes when you turn the ignition on. I have a map of the fuses and have checked them. All OK. Speedometer stuck on 70 mph. I have disconnected (and reconnected) the speed sensor but no change. I'll look at the threads you suggested. Thanks for your help.

[Peter_Bullen]

Hi Alan. Thanks for your reply. Yes I've checked that and its OK. (I even replaced it just in case). I also disconnected the speed sensor as you suggested. No change. The speedometer is stuck at 70 mph. I'm wondering how the speed sensor works. I thought it was just a magnetic pick up but can the sensor fail without blowing the fuse I wonder? Thanks for your help.

[Jonathan Kay]

EDITED: See #12 below.

I have disconnected (and reconnected) the speed sensor but no change.

No personal experience of this and haven't read all of the previous discussions. All corrections appreciated.

If it's shorting somewhere and affecting the instrument do you need to disconnect the wire at the instrument end rather than at the sensor end?

Jonathan

[Peter_Bullen]

HI Jonathan. Thanks - will try this. Peter

[Alan Reeves]

Pater, if you jack it up and take the wheel of you will see the sensor set up.

try revolving the disc on that side, with the ignition on, and see if yoiu can see the strobe light ?

To be honest of the speedo is stuck it surely indicates a stuck speedo ?

feel free to call 07768501962 in the next hour re speedo sensor set up

alan

[Jonathan Kay]

I'm wrong in #9 above. That should be:

• Disconnect the feed wire to the sensor at somewhere that is upstream of the putative fault.

Jonathan

[Jim 123]

As a sanity check, have you attempted to re - pair the immobiliser to the fobs?  Instructions in the Owner Manual.

After ignition is on, do the oil pressure and rev counter needles flicker within a sec or two of power being connected through?

Probably not related to the immediate issue, but if you have had a soaking, the barometric sensor on the top of the front LH firewall platform might have collected water. Normally the sensor aperture on the top surface is open and exposed when they come from the factory, and some owners put a length of bent rubber tube on this to ensure it breathes downwards.

[Peter_Bullen]

Hi Jonathan. I have just disconnected the speedometer but no change. Still stuck on 70 mph. I am wondering if the speedometer is damaged and if this could disable the ignition. Peter

[MADMALC]

Have you tried disconnecting the battery, counting to ten and reconnecting. It's an old 'trick' that sometimes works. Good luck.

[Jonathan Kay]

Obviously the speedometer isn't the most immediate concern but it is repairable.

Jonathan

[Peter_Bullen]

Thanks everyone for all the ideas and helpful advice. Also thanks to Rob from RatRace (great guy) and Matthew and Michaela at Caterham. I ended up swapping the ignition relay around with the one above (Matthew's idea) and it all sprung into life. I was beginning to think it was an immobiliser problem ..phew! Anyone else experienced this issue with relays? Now concerned it could happen again. Thanks again. Peter

[Peter_Bullen]

Hi Jim. Thanks for the tip re the barometric sensor. Think I will add a rubber tube as you suggest.. Problem fixed - fault was in the ignition relay. 

[Jonathan Kay]

Thanks for the solution. Isn't it convenient that it has a twin. :-)

As no-one here suggested that (IIRC) please can we run through the symptoms again?

• When you switched on the ignition did the charging warning light come on?
• Did you hear the fuel pump (and can you normally)?
• What did the immobiliser telltale light do?
• When you tried to start what happened?

Anyone else experienced this issue with relays?

They're commonly not seated, contacts and pins get bent and corroded and they fail internally. Sounds like yours did the last. Do you think that it was drowned?

Jonathan

[Jim 123]

Re ignition relay is there any trace of water getting into the fuse box during your deluge?

[Peter_Bullen]

Hi Jonathan. The fault occurred at speed. it was as though I had switched the ignition off and the immobiliser came on flashing 'normally'. 

I tried the ignition switch and nothing happened no instruments,etc absolutely nothing. The immobiliser still flashing and lights and horn working, nothing else.

I found that removing the battery earth lead and a 7.5 amp, instruments and relay drives, fuse  (all fuses ok) and then replacing got the fuel pump to run,  but no ignition and then with Robs (RatRace) help repeating the process for longer (ie battery disconnected for longer) and removing more fuses  (not sure which ones) and then replacing we got the engine to crank and the immobiliser light changed from flashing to permanently on, but still no ignition/instruments etc. Switching the ignition key to 'off' put the immobiliser back to flashing (armed) mode. Replacing the ignition relay solved it. I think it was an internal failure in the relay. No water inside the car... but it was very heavy rain!

Hope this helps.

Peter

[Jonathan Kay]

Thanks, Peter.

We should have suggested that!

Jonathan

[Peter_Bullen]

I have been reflecting on the relay failure causing the ignition to cut out and wondering what can cause a relay to fail? If there is a sudden current surge could the relay act like a fuse. ie a short causing a current surge causing the relay to fail. I guess I am pondering on the very wet conditions and still thinking that was the reason for the failure but there was no evidence of any water around the relays or ignition switch or immobiliser. Any thoughts?

[ChrisC]

I am no relay expert, but I suspect the relays used aren’t the highest grade component on the market, so its a simple supplier QA / component failure.    To melt a relay you have to go some, so a fuse will normally go long before a relay fails.  

[revilla]

Do you still have the failed relay? If you really wanted to know exactly how / why it failed you could carefully open it up for a look. I you're not sure you know what you were looking at, feel free to send it to me and I'll happily do a bit of a post-mortem on it for you. I agree with ChrisC above though, I think the most likely thing you will find is just a manufacturing quality issue. If not, it may just point you in the direction of something that needs investigating.