Hi Guys. I'm a newbie, so go easy
Have an XJ-SC (1986) V12. When the engine is hot, under any
acceleration (and in particular going uphill, it's
embarrassing), she coughs and splutters and occasionally
backfires.
I've changed the fuel pump and checked the filter.
Seems to only happen when the engine is hot.
It was suggested that the ignition amplifier module was the culprit so I purchased a new module from the States. It lasted
one 30min trip. Went to start the engine again and no spark
whatsoever. In pouring rain (naturally) I put the module
that was playing up back in (worked ok when cold). Drove for
about 15mins. Engine dead cut again. Tilt-tray brought the
car home. On looking at the whole module now, LOTS of burnt
wires mostly going back to the rear coil!!
I will have to replace the whole module housing, not just
the part so I can get all the new wires.
Damn!
These amplifiers are quite expensive and I'm interested in the possibility of changing to a single coil, which I presume has a different ignition amplifier. Therefore before I spend a lot of money I would like to gather your thoughts. Thanks. Rod.

 

I don't have any experience on the Lucas system only Marelli but now the other guys like Doug, Grant et al will chime in and give you some guidance.

I know Grant changed his to a single coil so he can point you in the right direction.

There are a number of options if you want to modify the system depending on budget. From simple mods to all out replacement of the ignition with an aftermarket electronic system.

BTW what suburb are in? I am in Casula if you need a hand.

 

A DAC6093 coil (Ducellier coil, Jaguar part number) works well to replace the original dual coils on the Lucas ignition.

I've heard of a faulty coil damaging the amplifier....but the burnt wires sounds extreme to me and probably points to a different problem....perhaps and old fahioned voltage-short-to-earth/ground


Cheers
DD

 

Hi Warren. Thanks. Just down the road...Camden South.
Rod.

 

On looking further, it has burnt and destroyed the two wires running from the module to the "+" connection of the rear coil.

 

Hi Rod

Does not sound good - I have a ROM if you want to PM me I'll give you my phone number and we can discuss while I read the manual.

Could be the balast resistors or a coil failure.

Also if your ingnition module is damaged we should be able to repair it.

******
EDIT removed incorrect information - found the diagram in the book, thanks Greg

 

The coils are connected in parallel, + to +, - to - on the Lucas HE V12 ignition system. The two can be replaced by a single more modern coil with the correct primary resistance. Grant francis is the expert on all this!

Greg

 

As I have not seen the aux coil I made the assumption it was a complete parallel coil system with the output of both coils going to the dissy. This is clearly not the case it looks like the secondary coil was an afterthought.

The secondary coil is only providing a boost (for want of a better term) to the primary coil input.

 

It is because the single coil of the time could not run 12 cylinders over about 3 to 3,500 rpm as the recovery time was too slow. Modern coils can do it OK, if of the correct resistance.

Greg

 

I think I will replace the two coils with the single coil suggested.
I presume that I still need the Lucas AB14 Ignition Amplifier? These seem fairly expensive. Where do you guys get them from?
I also want to relocate it, possible inside the mudguard. I think I saw somewhere a relocation kit?
Thanks. Rod.

 

Hi Rod

If you want I'll have a look at your module this should be fixable as long as it not potted in compound.

 

Here's a photo I just took.
Note the burnt wires in the unit and also on the coil.



Regards, Rod.

 

Have you measured the resistance of the coils? both primary and secondary.

I suspect you have a dodgy coil - even one shorted turn in a transformer can cause enormous current flow (which is what fries the wires).

Do you have a multimeter?

 

Rod, sent you a PM.

In the mean time I reread the thread (Merlot in hand) and that Kodak tells me a lot.

See that small capacitor with the burnt wire, MMMMM, unplug it from the module, undo the screw securing it, throw it away. It has shorted to earth, VERY common. I DO NOT run that little piece of &^%$ in any of mine, and NO interference of any sort. Yours makes 7 I have now seen with that item causing grief, although the burnt wires is a first, congratulations, you have done well.

I use an Echlin module TP45 is the part number, and some may be TP45B, the B means "blister pack", seriously????.

My suggestion is to replace the module, coz I reckon it may have taken a hiding with that unit shorting. ALso I reckon one or both of your coils is the root cause of the problem, so a replacement is extremely high on my list. I use a Bosch MEC717 "T Coil" as a stand alone coil. Did one today, sweet as, goes like stink NOW.

When you put that new module in and screw it down to the casing, take REAL CARE that the insulation on those wires is NOT compromised and shorting on the casing. They are real close, so just take the time and be sure. There are too many wires in there in my opinion, but I have had no issues as long as you use good old common sense.

My amp is out the front of the radiator, basically where the 2nd coil used to live, and 12 years on is NOT complaining. I have a write up on that and many other fixes I have done over the years, BUT, my success with attaching on here is dismal at best, so I will happily PM them if your email is provided. Some of the files are BIG, so be aware.

 

A big thanks to Warren and Grant for your help.
I will go along the way of replacing the coil and module.
Regards, Rod.
Will keep you informed.

 

Ok guys here is the latest.
1) Capacitor with burnt wire - removed completely.
2) Original two coils removed.
3) New coil mec717 purchased and installed.
4) New Napa Echlin TP45 Ignition Control Module purchased and installed.
5) The amplifier then relocated (and it fits perfectly) to where the front coil was situated. Just needed longer bolts to secure it. (obviously the wiring was lengthened).
Took it for a run today. Puuurrrrrfect.
Thanks for forums.
Rod.

 

Just when I thought I'd fixed it all .....
Went for a long run today. An hour each way. The old girl would cut out mainly after I went around a round-about. This leads me to think that it may be a fuel problem (as well). Any thoughts?

 

A friend just suggested that it may be that safety (inertia) switch on the drivers door pillar. Thoughts?

 

Did it die totally or just cough and splutter?

From memory the inertia switch cuts the fuel pump so the engine will run for a few seconds then cut out. You could try wiggling the switch.

 

Mmmmm, Bugga.

Not sure on the Cab, but on the Coupes, the fuel supply from the main tank TO the sump tank can get hissy due to the crud INSIDE the main tank blocking the feed pipe, and around corners etc can have it splutter.

Then there is the infamous sump tank, and the pick up filter that also blocks up with crud, and causes all sorts of issues.

Mine got hissy waaaaay back in 1996, after much messing with all suggestions, and no real fix, I removed the filler cap, all good, DAMN, and since some gem had messed with the tank venting system (a fix on the list of "to do"), it was not venting, hence running issues on an intermitant scale.

Warren is right, the inertia switch is an "on/off" for the fuel pump, and I have never seen one "splutter", they do just die, as does the car. A reset will do NO harm however. If in doubt simply join the 2 wires for a test, DO NOT leave it like that permenantly for safety reasons.

Another test you can do simply would be to locate the fuel pump relay in the boot, pull the relay, and bridge the 85 and 87 terminals relative in the socket. That will have the pump run at all times the ign is ON, so be careful. This will eliminate the ECU, and the relay from the diagnosis.

I know its a few things, but I do also believe it is a fueling issue, to give the "splutter" you are mentioning.