On holiday in France, 13th time in her and for the first time ever she is misbehaving. About half power. I am going to need some good advice and maybe help. I am on a dodgy connection so let me post up the car details and symptoms first. 1989 v12 he with marelli ignition..twin coils.
set off last Saturday in the UK . Just after I pulled onto the motorway it was mot pulling well. Power down. This lasted for about 10 seconds and then all of a sudden back to normal. I did not turn round...let's get the ferry!
240 miles of perfect driving later..onto the ferry
800iles total to the destination in the south of France, all was perfect. That was Sunday.
Monday a 20 mile drive around the area and perfect.
Tues to today did holiday stuff with Mrs something somewhere then today tried starting her.
started up but but would only idle with partial throttle.
had to do a journey of 15 miles total.
underpowered all the way...apart from editing the holiday location along a 3km single track road someone came hurtling towards me around a blind bend.
hammer on the brakes then for about 2 seconds the engine ran sweet with full power.
full power not seen since.
strong smell of unburnt petrol around the car.
i stopped a bit into the journey, after a big hill that we crept up and the right hand tail pipe was very hot but the left hand one far cooler.
I am thinking wiring to one of the twin coils.
But I have to fix this. Ferry is booked for the 19th.
You guys more experienced than me, I need your help. What is the most likely mode of failure and how do I test for it?

 

Offhand it sounds like the beginning of the dread Marelli ignition failure

Possible burn thru of ignition rotor or failure of coil, or failure of ignition module.

A visual inspection can confirm the rotor possibility.

Don’t drive the car

More later and/or others will chime in.

Cheers
DD

 

it is certainly the dreaded marelli failure. You have a duff/malfunctioning amplifier and maybe a burned distrubutor cap and rotor. You should not drive the car as it is dumping unburned fuel into the hot exhaust side which is burning in the catalyst.
From what you describe this could be caused by a poor wire connection to the amplifier, as it seems to be intermittent. have a look at thhe the wires to the amps and from them to the coil.

 

OK well harnessing my inner pessimist, I travel on holiday with hard copy of the factory workshop manual and parts list. I was a little dismayed on the distributor page to see for 89 my on distributor DAC 4758 have listed for both the cap and rotor the helpful information "tba" hmmm.
but anyway time was going to be critical and if it needed it, I was happy to buy two new coils and amplifiers a new rotor arm and cap just to get them here.
but from sng Barratt France each amplifier was an eye watering 457 euros,which would have taken the shine off my holiday, so I thought I would take them off clean up the tetminals and heat sink, put them back on then start her up for about 30 seconds,. Then feel the exhaust manifold down pipes to confirm which bank was running, then swap them over and repeat. If the hot downpipes swapped with amplifiers then one was not working
if the same bank stayed hot regardless of amplifier then I had no need to order any amplifiers.
well as it turned out a couple of the seven pin connectors looked a bottle the worse for wear on stripping so there was a bit of a clean up and application of agent wd40, and back together it went.
start up was perfect. A test run was great.
so for now, all looks good.

however, all those doom tales!!!
I thank the lord I did not have a catalyst car.

thanks for the pointers DD and Greg.

when I have a better connection I will post up the part numbers of what I would have ordered.

i also need to take a photo of my modest tool set I have with me all laid out. step two would have been coil swaps and the same test to identify which , if, any coil had failed and then it was the distributor and rotor arm. Quite a bit to take off there. I will now change those in the winter.
Thanks ,
something somewhere

 

Fantastic on the trot diagnosis and fix.
Hopefully did not interfere too much with French wine imbibing

 

Yes, need to keep things in perspective. Mulled over today's order of battle last night over salmon, new potatoes green beans and a nice Hollandaise type sauce all washed down with a chilled rose.
Tonight, beef and a lovely red.
No need to call those breakdown people yet! 😉
Amplifier, coil, cap or rotor, it was all going to be fixable.
Weather forecast for next week is in the 30s and hood down all week.
Mrs somethingsomewhere is used to me getting my hands dirty on occasions.
Only compliments everywhere about the car.

 

The coils for the marelli are pretty cheap all things considered - the same design was used on lots of cars so you can get NGK & other reputable branded ones for not much money.

Where are these ignition amplifiers located out of interest?

 

Glad you seem to have it sorted.

When you get back home, re-clean everything you cleaned with WD40 with a proper electrical contact cleaner. WD40 doesn't actually clean anything, the solvents it is suspended in do the cleaning and will work in an emergency, but they quickly evaporate and the remaining WD40 is an aluminum protecting coating that quickly turns into a gummy dirt magnet that leaves the contacts in worse shape than before.

Enjoy the rest of your trip.

Cheers

 

On the radiator top panel.

 

OK back home now after an absolutely brilliant holiday.
Parts I might have needed
2 x ignition module DAC4607 (aka amplifier) becomes DAC11520 on top of the crossmember above the radiator. Diagnosis - swap positions and see if non functioning bank moves with the change.
2 x coils DAC4608, in well of vee one below the other. Diagnosis - swap positions and see if non functioning bank moves with the change.
1 x rotor arm JLM1911 inspect and change if sign of arcing to short.
1 x distributor cap JLM1909 inspect and change if signs of eroded terminals within cap.

What will I do before next year? Remove and inspect all. Clean up all terminals on the amplifier, coils etc.
What will I take with me? Well space for an amplifier and coil is easily found and since they will fail without notice and it is unlikely two of either would fail simultaneously I will take one of each.

 

Some shots from the holiday. Super weather. One night of storms the rest sunshine. A couple of days were 35°C. Mrs Somethingsomewhere interested in something in the footwell there after the lunch stop.

Going down - we were off the ferry in the morning and at Grenoble for 1pm with just a single stop for fuel, coffee and croisant at Auxerre.

 

Possibly the first time I've seen a hitch on an XJS; though I have a facelift, could I ask which brand / model hitch and bike rack you fitted? Any issues?
Thanks!

 

Beautiful pics, looks like perfect GT country

 

Ideal for the perfect GT!