AJ6 ignition system malady. anyone seen similar ?

[mikele pirelli]

Hi guys, while rebuilding our 4.0 XJS and refitting the ignition system
I appear to have no spark !

This is the AJ6 single coil, ballast resistor, empty dizzy setup.

Tried all the usual stuff, ie no HT to distributor main lead, so
obviously none to plugs either. Rotor arm, cap, leads and plugs all
good.

I seem to have switched 12v ok to coil primary hot terminal (+ve,t15 )
but...
also constant 12v on the low primary terminal also (-ve ,t1 ) So, it
would appear that the ignition amp module isn't switching to ground.
( DAC 7317 ) type.

Hence no HT on coil o/p as a result... so ignition amp is prime
suspect at the moment, anyway.


I've not got to the point of replacing this yet, but an oddity I've
come across is that the condensor is coming off the POSITIVE ( t15 )
side of the coil primary ?

I came across an AJ6 pdf diagram which seems to verify this is
correct.




My VIN is approx 182XXX, ie pre AJ16.

If anyone has worked on one of these would you mind confirming
I've got this right !

I'm an electrical equipment engineer, so I can read a circuit
diagram ( usually ) But before I start shelling out on ignition amps,
crank sensors, etc. If anyone has previously worked on this setup, I'd
appreciate hearing from you and benefiting from your experience. As
I'm a relative novice on Jags.

Edited by mikele pirelli on Monday 16th May 22:57

Edited by mikele pirelli on Tuesday 17th May 00:31

Edited by mikele pirelli on Wednesday 25th May 19:00

[Jaguar steve]

Never verified this and not even sure if it applies to the AJ6 version but have read to check if there's a flicker of movement on the rev counter as you turn the engine over. If there is then the crank sensor is OK, if not then it's the prime suspect. That may not be the answer or that diagnostic path may be compromised by another as yet undiscovered fault but it'll cost nothing to try.

[mikele pirelli]

Jaguar steve said:

Never verified this and not even sure if it applies to the AJ6 version but have read to check if there's a flicker of movement on the rev counter as you turn the engine over. If there is then the crank sensor is OK, if not then it's the prime suspect. That may not be the answer or that diagnostic path may be compromised by another as yet undiscovered fault but it'll cost nothing to try.

Thanks for that one Steve, I'm just back from buying a new battery as
I know the existing one is weak anyway. I'll look at the crank sensor
indication you speak of on the tacho when I fit the new battery and let you
know what I find.
I appreciate the input.
Regards... MP

Edited by mikele pirelli on Thursday 17th November 10:56

[mikele pirelli]

Hi Steve.
I retried the car earlier with new battery and as you thought
I got the flicker on rev counter when cranking over. This then would seem
that crank sensor is functional as you said ( I cleaned the plug pins on
this first )
So, we'll start changing parts now until it works. Unfortunately, I've
no other AJ6 to swap bits over with, which would have saved a bit of time.
I'm in no particular hurry as the car is in full rebuild anyway.
I'll let you know what the final outcome is. Thanks again.

[dbdb]

Have you tried Jag-lovers? There is a lot of knowledge about the AJ6 engine on there.

http://forums.jag-lovers.org/

[Jaguar steve]

Eurojag will be able to help with sourcing s/h parts.

[mikele pirelli]

Thanks for the advice lads. I'll look at the Jaglovers site. Yes
I've used that supplier before Steve, quite good to deal with.

Usually when changing components on this sort of thing : from
the engine running, I'd change one component... test, the next
and test it's still running ,etc. Until I'd replaced everything I intended
to replace.
This admittedly is a bit of a plod, but if it induces a fault then it's a fair bet
it's the last thing touched that caused it. Rather then change ten things
at once and wonder then , what's caused the problem.

But by the nature of the work this time, the whole car has been in bits !

Consequently, it's become a process of elimination now. So, I'll just
replace everything important one item at a time , I think.
At least I'll know it's all new stuff at the end of it. Thanks again,

[mikele pirelli]

Final update... we have ignition !... she bangs !
: diagnosis a £4 condensor and a can of switch cleaner !
So no expensive electronic components required unless
just to retrofit new for old.
Thanks for the advice...
MP.

Edited by mikele pirelli on Thursday 17th November 10:56