In the old days we had ignition points inside the distributor. They opened and closed to 'trigger' the coil. The ignition amplifier serves the same function but without moving parts. So, yes, if the amplifier is inoperative the coils won't work...and there will be no spark


Faulty coil wire....the one from the coil to the distributor cap. Or corroded sockets at the coil or cap.


I don't think so. The ECU does not signal the ignition system in any way. But the ignition system signals the ECU


The starter is now operating? What fixed it?



That would be pin 26

The most common failure point in the ignition system, beside wiring/connector faults, is the module inside the amplifier.

There is an easy test for the ignition system. I'm sure it's in the archives. Post back if you can't find it. Search "CEI Test" or similar

Cheers
DD

 

Adding to Dougs information.

Unplug the Mini Loom that goes Amp to Distributor, AT the Amp end. Probe the 2 wires, and note the resistance you get. I forget, 3 coffees, around 3 Ohms I think,but that loom is known to fail internally, so any Ohm reading would give a hint that the Mini Loom is OK.

INSIDE the Amp is a Condensor looking thing, held into place with a small self tapping screw. Remove it, BIN it, they leak to earth and KILL the spark in a heartbeat. Sometimes intermittent sometimes, legs up.

 

Hi guys,
I found that one of the wire of the pickup was broken. I soldered it. Now résistance is around 3 Ohm.
everything works,
fuel pressure at 36 Lbs,
injectors working,
new coils,
spark coming out of the distributor lead,
spark going to the spark plugs.
However, when I crank the engine it giggle and want to start but does not.
I purchased a new MDS GM amplifier which I will change tomorrow just in case the one I have is not working to it full potentiel.
Aside from these what else should I look if still does not want to run?

 

OK, some thoughts.

You have spark AT the spark plug where the lead attaches, good. How old are the spark plugs??. Old spark plugs do not spark at the tip as needed, and that will cause what you have.

The Injectors are :clicking", good.
You have pressure AT the Injector, good.
Are the Injectors spraying fuel inside the engine??
I would lift one of the #1 Injectors out, and place the tip in a glass jar. Crank the engine. Note the fuel in the jar, or lack of. Just because they "click" does not mean they are spraying fuel, BUT, for all 12 to be Dud, not likely, but you need to start somewhere.

BE CAREFUL, you are playing with liquid that goes BANG very easily.

If there is no fuel in that jar, Injector triggering is the issue. That list is short, but involved.

 

Thanks Grant,
I ll look into it. I purchased the GM ignition module which goes into the amplifier. I ll chaqnge it.
Question about the timing: how hard is it to get the right timing? when you rotate the distributor couple of hairs, is it enough to prevent the car from running?
thanksa

 

Timing:

NOPE. There is 30 degrees variance in there 360 Div by 12.

The main issue over all my years with these very simple engines is that Freddie Fiddler guy, then the basic unknown.
Hence the quiet, systematic approach.
One step at a time without re-inventing anything.

Spark is GOOD, eliminates lots of things.
Fuel to the rail, GOOD also.
Fuel inside the engine, GOOD on a better scale.

Thats the basics on any engine to make it run.
Fuel not too much, not too little, CTS controlled primarily, then the VAC supply to the ECU. MORE Vac = LESS fuel, and vice versa.
HOW WELL it runs, AHA, that is where the BEER comes in.
Timing, #1A (For V12 Engines in Jaguar), is the key cylinder, and the timing marks under the front are related to that, IF THEY ARE STILL WHERE THE FACTORY SET THEM, and not slipped on the vulcanized pulley wheel.
That is why, on any unknown engine, a soft wire down #1 plug hole and rotate by hand on the Compression Stroke, and when that wire stops rising, presto, TDC Comp Stroke #1 cylinder. Obviously #1A on this engine.
GUESS WHAT, it will run at TDC, maybe NOT well, but it will run, and trimming the timing by 10Deg or so once running is SIMPLE.

As I went through earlier, #1A is a major PITA to access. So I use #3A, and the corresponding post in the cap as my marker, the rest is just simply one following the other.

Remembering the direction of Distributor rotation is Anti-Clockwise when looking down at the top of the cap, and the leads are fitted following the same rotational direction.

V12 thoughts on THIS engine:
If its got a Blue spark, move on, all that stuff is working as designed. Maybe some updates later, when its running.
Its got fuel at the rail, but the fuel entering the engine is still an unknown. The spray test of either #1 Injector is ONE way.
Spray some Starter Fluid, Ether, up the air cleaner snorkels while someone crancks it. It that makes it alive, you KNOW the Injectors are NOT working. ALL 12, OOPS maybe a loom problem, all 12 to stop at once, better odds at the Lottery.
There are other wires at play, the Shielded wire to the ECU is another that will stop the Injectors operating.

If not already, read this attachment, and follow through the steps.

The fact its trying to start means whatever it is is simple. I know you have sorted the plug leads at teh cap, but please go and double check them again, and I mean NO disrespect, I have screwed that up more times than I care to admit.

 

Hi Grant quick question
in one of you Comment you suggested that we remove the second fuel pressure regulator. Will this affect the fuel pressure in bank B?

 

Removing what looks like a Fuel Pressure regulator, on the A Bank, will have NO affect to the rail pressure at all. That A Bank FPR was a pulse damper of sorts, and causes a lot of running issues, mainly at idle, and pump issues.
I only ever had Idle issues until it was gone.

Later cars, as in 6ltr, only had One FPR.

 

Just make sure I got it right. My Jag is A North America car with the steering on the left side. Which one of the regulator can be removed the one on the left or the right?

 

The FPR on A bank, the RHS as you sit in the car, can be removed. The reason is that it does not control fuel rail pressure as it is on the pump side BEFORE the rail, and was on later cars deleted by the factory.

The FPR on the B bank side DOES control the rail pressure as it is downstream of the fuel rail, thus in effect "damming" the fuel to create pressure upstream.

 

JP

Apologoes for going Aussie and Jag Speak, when you are new, oops.

ALL RH, LH etc is taken when sitting IN the drivers seat, facing forward. That way, the placement of the steering wheel or anything else matters not.

A Bank = RH side
B Bank = LH side
FPR = Fuel Pressure Regulator
CTS = Coolant Temp Sensor
ATS = Air Temp Sensor
TPS = Throttle Position Sensor
HT = High Tension = Spark Plug, related to the leads from cap to plug etc.
PCV = Positive Crankcase Ventilation.
Petrol = Gas = Fuel = Bang Juice.
AAV = Auxiliary Air Valve = Cold Start Air Valve.

There will be more, of course, but thats the basics.

 

When I tried to start the motor today no spark going to the spark plugs, check the résistance on the pickup, no thing. Either one of the wire is cut or the pickup itself it kapout...
I think I m going to buy a new pick-up coil and be done with it.
Everything else looks ok

 

JP,

A good idea.
I am hearing more and more of these pick ups dying, but have noit had the pleasure down here.

Some cars have a connector in that mini loom, Amp to Distributor, some do not.

One guy here found the joiner in that Mini Loom very corroded, and once cleaned, SPARK, Blue and Strong.

All mine had no joiner, just the wires all the way to the Amp.

 

A thought on ignition modules: Use nothing but the genuine GM module ( or AC Delco part #D1906). The V12 pushes the module right to the edge of it's design limits, in the way a V8 doesn't. I had ignition trouble once, replaced the module with a new aftermarket module, problem remained.

Went to the junkyard and took the module out of a late 1970's Chevy truck ( which was either the original module or a dealer replacement - it was marked GM on the case) and the car started right up with no further problems. So I'm a bit gunshy about using anything other than a GM module in the V12.

 

Hi Grant,
I checked again this morning the pickup. There is actually resistance between the two wires however the little magnet under the pickup is cracked in two (looks like this is very brittle). I guess that is a show stopper for signal right?

 

Not sure on that.

A snap, not too close, of the offending item would help me atad.

I have near zero issues with that pick up in nay of them, apart from the broken wire fiasco already discussed.

More thoughts today while having X Rays.

You mention the loss of spark one day to teh next.

Simple thing, FREE, whoopee.
Remove the White wire from the Ignition Coil. +ve terminal.
Make and fit a wire from the battery +ve to that terminal on the coil.

THIS WILL HAVE THAT COIL LIVE ALL THE TIME THAT WIRE IS CONNECTED, SO DONT LEAVE IT THERE ANY LONGER THAN NEEDED.

Crank the thing, see it the spark is there.

IF SO.

I think the Ignition Switch Electrical Section is in dire need of a service. PDF attached.
Issue here is the switch gets gummed up with old grease.
When at Ign ON, the White wire on the coil is battery volts.
When going to START position, that White wire should still have battery volts, or very close.
With that switch issue, the battery volts is lost when going to crank, hence NO spark and other things not working. VERY COMMON issue now with age and lack of use.

 

Hi Grant
I cleaned the ignition and put Electric lubricant.
I check the spark coming out of the coil and it's good.
The spark going to the spark plug is very weak. A small yellow arch which leads me to believe the the pick-up is the culprit. I connect à wire from the batterie + and the + coil, same result.

 

JP.

1st coffee, so look out mate.

That pick up etc etc is ALL OK.

There is a problem with:

Rotor.
Carbon brush contact in the Cap Centre post, this contacts the rotor and transmits the spark from the coil to the related plug post.
Old spark plug leads.

I know you have a new cap, good.

Remove the cap, turn it over, look at the 12 segment points. Where is the "arc" mark from the rotor tip. It MUST BE about 2mm++ up from the bottom edge.
This is called rotor height alignment, and is now becoming common with the lousy replacement parts we get.

ALL mine were "arcing" right at the bottom edge, Yellow Spark at the plugs. I removed the cap gasket, better. Then I hand filed a Fibre washer to go inside the rotor, so it sat 1MM higher on the shaft, FAT BLUE CRACKER at the plugs.

Remember, the gap between the rotor tip and the cap segment is an AIR GAP. Many people clean the tip of the rotor and the cap segment, OOPS. That gap is now too big, and spark energy is GONE.
It is a precise thing we take for granted. New cap and rotor, good to go???, not always with the V12.

There is more, but "medical carer duties" for the wife calls, I will come back after that is done.

 

OK, all done and settled for a few hours.

Another issue I have had 3 times now.

Crap rotor material, the spark from the coil, good and FAT, goes through the carbon brush to the Rotor Brass Strip, BUT, the Rotor Insulation allows this energy (spark) to penetrate the rotor and track to earth via the Distributor Centre Shaft. The 1st one took weeks to actually find.
It was when doing the rotor height adjustment that I saw the feint witness marks on the shaft. The Fibre washer I used mad a HUGE difference, but not quite what I wanted. They were all Echlin, Made in USA, Rotors and Caps in those days. I ventured to the Dark Doors of the OE market, and got a Jaguar Rotor, That sorted it, the FAT Blue Cracker at the plug was scary, even to me.

I doubt this one, but, again, its FREE to sort. Look carefully at the Engine Earth Strap Fiasco around the LH engine mount bracket. They are CRAP at best. Remove them both, clean them, and the contact areas WELL, refit with a smear of grease. That is the weakest point of the V12 when chasing odd electrical happenings. Run a dedicated Earth strap, Engine to Chassis, thus eliminating that Fiasco.
The original is Engine to Cradle, Cradle to Chassis, DUH.

If what I suggest is not clear, ask, and I will simplify it, I do tend to assume too much some times.

 

Hi Grant
took few weeks off from my Jaguar project.
New pick-up coil installed, new amplifier, gas going to the spark plug, injectors clicking well when cranking engine, gas pressure ok. Good spark going to the distributor , average yellowish spark going to the spark plugs (not blue)
the engine want to start. It did start for a few second but stopped. I player with the timing screw when cranking the motor with little succès. Could not find à vacuum problem.
Not to sure where to go from here. I feel that I m close....
thanks