XJ12 series 3 non-starter

[David27]

Hello all
I've got a 1979 series 3 XJ12 which is refusing to start. Have tried all the obvious things eg. spark plugs, ht leads and fuel is getting to the cylinders. It has been off the road for over a year now, stored outside with a cover on. I had a mobile mechanic take a look and he reckons it's the ECU but I can't see why that would suddenly fail and they seem as rare as hen's teeth. Any help or advice would be gratefully received!

[steviemac]

It's probably a bit obvious and I'm not really a mechanic, but have you used new fuel. Recently I had a similar problem with my Daimler. It turned out that the fuel had 'gone off' and I used some I'd had in a can for a while. This was also useless. New fuel worked however. It may be some use as I presume ther is a spark and the battery is fully charged etc. Good luck in any case. Steve McGonigle

[steviemac]

It's probably a bit obvious and I'm not really a mechanic, but have you used new fuel? Recently I had a similar problem with my Daimler. It turned out that the fuel had 'gone off' and I used some I'd had in a can for a while. This was also useless. New fuel worked however. It may be some use as I presume there is a spark and the battery is fully charged etc. Good luck in any case. Steve McGonigle

[David27]

Thanks, I'll give that a try.

[simon4253]

hi david did you manage to start your v12? I take it there is a good spark at the plugs? take out one of the easier ones and see if they are wet.If they are and the spark is good try knocking inertia switch off so fuel pump doesn,t run and press it down again if it fires. ngk plugs do not cope well with being flooded so check spark at all or substitute with some others you know are good.If the above works it may be ok after a good run but continuous flooding will drop compression making starting difficult. check and clean connections to all sensors. good luck and happy new year

[CliveRothwell]

Hello Dave

I'd also go down the "put new fuel in it" route. There is plenty of pipework volume involved here. I'd consider draining one tank and refilling it with brand new fuel. Easystart may well be worth trying. Do ensure that the battery is also fully charged - 12 hours possibly if it hasn't been on a trickle charger or until the cells can ALL be seen to bubble when you take the caps off. Read up on health and safety re charging batteries! A charged battery will give you a fat blue spark if the system is functioning correctly. I'd try the battery first before you replace the fuel as the car will start with the good fuel in and a good battery less one cylinder! Let us know how you get on - we all love to try starting awkward cars!

[David27]

Thanks guys, for all your suggestions. Just to give you all an update - I tried new fuel but that didn't work, the battery is brand new and fully charged, checked spark - all ok. Eventually I bit the bullet and sent off the ECU for testing, I'm now £66 lighter and it came back with a report saying it is faulty but they wanted £450 to fix it! I doubt the car is worth that at the moment so I just got it returned. So now I'll just have to try and find a second hand ECU for a more reasonable price or someone who can re-furbish them for a lot less than £450. The concern I have is that the report on the ECU said the damage had been caused by a power surge or something like that so I probably have some other fault that caused it to fail in the first place. If anyone out there is breaking a series 3 XJ12 please let me know.
Cheers, David

[David27]

Hi I just thought I'd post the latest on my XJ12 woes! The poor old thing has now sat at the back of the drive for 2.5 years, with only a cover to keep the weather out. The engine is all back together with new water pump etc. but she is still refusing to start, despite a replacement (2nd hand) ECU. One of my workmates suggested the timing could have been altered when we changed the water pump - can anyone advise if this is probable because it would maybe explain why it is trying to start but just won't carry on running. It's very frustrating because it seems like I'm nearly there but can't quite pin down the last piece of the jigsaw. Any advice would be much appreciated.
One of these days I'll make it to one of the shows, but not this year I think!
Regards, David