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I agree, it must be electrical. The last video is quite clear.
I'm also thinking it is not just 1-2 cylinders missing now and then. It's more like 6-8-12 cylinders missing most of the time, and if it was sparks jumping in wrong places the leads and/or cover would have serious marks.
I would like to have a spare ignition amplifier ready, so I will look for one.
For the pick up module: I tried moved the wiring outside the dizzy when the engine was running, no change.
How much more than removing the leads and cover, rotor, transparent cover plate is involved ?
Will I have to take some of the advancing mechanism apart to access it ?
I will receive a new injection harness made from top end parts next week. that will most likely be the next thing I will change, unless checking the pick up wiring is fairly straight forward. I have tonight and then Sunday to work on the car in the coming days.
check the starwheel for condition (no broken points)
starwheel to shaft clip carefully removed with snipe-nosed pliers so you do not lose it
starwheel carefully off spindle
I think you can now see the whole thing, part of which connects to the vac module arm. Just very carefully check the two wires that go through the rubber plug-like bung on the dizzy base and also the plug after the dizzy base in the wires going up to the amp.
FWIW, I feel the amp is more likely your cause...
Greg
In the snaps, and the flash is masking what I suspect, the "spark jump" appears to out the top edge of the rotor tip, and WAY down near the bottom of the cap probes.
The Echlin caps I used way back did that, and I simply discarded the cap gasket, thus lowering the cap about 2+ mm, and this brought the rotor tip more in line with the inner face of those probes, and solved many issues, mainly with the Red car.
Quality of replacement caps and rotors now is horrid, so we have to be a tad more vigilant that plug and play..
Greg is spot on with the amp, and modules. I use Echlin only, and have had no issues, but it has been a loooong time between drinks.
Any stray sparks is a suspect lead quality. I too, use Magnecor standard spec, nothing special, usually Black, and have no issues, V12 or 6 cyl.
Last edited by Grant Francis; 08-31-2018 at 06:32 AM.
I think what you spotted is correct, Grant. I just zoomed my pics, and the tracks are for sure not on the middle of the 12 pins. My gasket is less than 1mm, but I will try to leave it out and see what I get out of that.
I will do a few snaps more with focus on track position.
Greg: I will leave the pick up alone for now and try to source a working amp. Mine says Lucas AB14, and I can find many of those at varying prices. Any recommendations for suppliers if I don’t find a used original ?
Last edited by leo_denmark; 08-30-2018 at 11:10 AM.
I hear you. It just hurts a bit to throw out a 200$ set of leads after 2000 miles...
True. But you need all the sparks.
Its a harsh and tight environment down in the vee. I went ahead and made my own wires with giant 10.4mm Taylor wire. It’s actually just jacketed 8mm, but I figured that if there was ever a engine that these made sense in, this V12 is it.
Greg: I will leave the pick up alone for now and try to source a working amp. Mine says Lucas AB14, and I can find many of those at varying prices. Any recommendations for suppliers if I don’t find a used original ?
My engine is from an 89 XJ12. My amp is listed as DAC2673 DAC4104, but do anyone know if there is any difference ? They look very similar except from price...
Yours is an '85, and you use the 81-84 amp with good result ?
Edit: Found this in another forum: The difference in the amplifiers seems to be the external wire connectors.
Leo
Last edited by leo_denmark; 08-31-2018 at 06:07 AM.
Reason: Wrong part number...
I have just read the ignition related pages in Kirby's book. I should have done that a long time ago, or just listened more to what Greg has been saying all the time: Ignition amp !
From the book:
During most operation, the ignition amp is merely switching the current on and off and is dissipating very little heat.
However, at low RPM when it’s having to cut back the voltage to limit the current in the coil, it’s having to dissipate
that extra power. It gets hot under such conditions. The amplifier is bolted to the aluminum intake manifold to try to
dissipate some of this heat to the manifold and to the cool air passing within.
This describes my problems very precisely: Misfire when driving slowly, getting worse the warmer it is or after a good motorway stint.
I lowered my dizzy cap 1mm yesterday by removing the gasket as recommended by Grant. Sparks was jumping 'on the edge', but I think it was OK before. Now it must be better though !
Leo
As someone added, the amp difference is just the connector to the dreaded white wire, no problems changing that if required. I have done Grant's "move the amp" mod; BUT, PLEASE, get the car going properly as OEM before doing so! You have to extend SIX wires, and it is easy to introduce yet another difficulty, so get the thing running right and then do Grant's very worthwhile mod, is my best advice.
Also, take very great care to waterproof all the various holes into the amp where wires etc etc go into it, when you do move it in front of the rad (not a problem in Oz, obviously!).
Coming in wayyyyy late here. No matter, you've already got the best brains involved. But I'll toss in a few random comments
Originally Posted by leo_denmark
When listening to the video it's my impression there are drop outs in the injector pulsing. Any thoughts ??
It would make perfect sense because the F.I. system depends on a trigger signal from the ignition system to operate.
I may have missed something trying to play catch-up but, if I understand correctly you're waiting for a new F.I. harness to arrive, yes? Personally, and since you've already covered so many other bases, I'd be sorely tempted to hold off on any additional excursions and expenditures until the new F.I. harness has been installed.
Faults with the injector harness are well known and, in my experience, random injector drop-outs can give a symptom indistinguishable from an ordinary ignition misfire.
Leo
As someone added, the amp difference is just the connector to the dreaded white wire, no problems changing that if required. I have done Grant's "move the amp" mod; BUT, PLEASE, get the car going properly as OEM before doing so! You have to extend SIX wires, and it is easy to introduce yet another difficulty, so get the thing running right and then do Grant's very worthwhile mod, is my best advice.
I agree, and was just going to suggest the same. Find and repair faults first. Upgrades and improvements second.
Cooler components are good....but not a requirement for a misfire-free V12.
I recently had my V12 out for an 80 mile drive at 60-80 mph, in 95F/35C weather, and she ran like a watch....with all components in original locations.
I agree, and was just going to suggest the same. Find and repair faults first. Upgrades and improvements second.
Cooler components are good....but not a requirement for a misfire-free V12.
I recently had my V12 out for an 80 mile drive at 60-80 mph, in 95F/35C weather, and she ran like a watch....with all components in original locations.
Cheers
DD
I follow you and will do just that. My XJ-S also runs like a clock at speed, it when I’m going 30-40 MPH things go bad...
Leo
As someone added, the amp difference is just the connector to the dreaded white wire, no problems changing that if required. I have done Grant's "move the amp" mod; BUT, PLEASE, get the car going properly as OEM before doing so! You have to extend SIX wires, and it is easy to introduce yet another difficulty, so get the thing running right and then do Grant's very worthwhile mod, is my best advice.
Also, take very great care to waterproof all the various holes into the amp where wires etc etc go into it, when you do move it in front of the rad (not a problem in Oz, obviously!).
Just checked my connector, it seems to just be a double spade in a common housing. If I buy the cheaper DAC2673 and it turns out my current ignition amp is DAC4104: what connector modifications will I have to make ?
Took a look at the engine running after a drive in the dark, and I do actually see occasional weak flashes. It's nothing like the sparks a spark plug makes, but nevertheless: Some sparks are escaping...
I then did a drive with camera strapped to the fuel rail over cylinder A3. I managed to catch really lousy running, and I do not see i single flash in the video. Maybe a cheap actioncam is not capable of filming these ultrashort flashes, but I think we can conclude it's not like a discoteque under the bonnet. Youtube
Im curious as to why you feel this is ok.
You saw HT arcing occurring. Camera sensors are not going to be sensitive enough to detect them. You know that every one of those sparks escaping the HT leads is a missed cylinder. The go one place only. Not a weaker spark at the plug, no spark at the plug.
If you had occasional injector discharges into the vee rather than into the intake you’d fix that straight away, I assume.
You may may have multiple issues. We don’t know. And I have sat and figured out exactly what MUST be wrong on my jag dozens of times, only to be proven wrong.
In my opinion, if you find an issue with any part you should correct it. It may not resolve the issue you’re trying to fix, but eliminating possibilities is one of the few reliable methods available.
Leo
JJJ absolutely correct about the HT arcing.
Not that plug in your photo, which is the loom from the dizzy pickup that plugs into the side of the amp, that is the same on all amps. The only plug that might be different is the one of the four that emerge from the inside, V facing, edge of the amp, the rearmost one of the four that goes to the dreaded white wire plug - as mentioned above in my previous post (no. 73). That can just be changed for something suitable if needed.
Last edited by Greg in France; 09-02-2018 at 07:53 AM.
I expected this to be the connector in question as I knew the other ones were single connectors placed on the wires, which could be changed easily. This connector was the one that could cause a bit of trouble if had to change it.
No sweat then, I order the not-so-dear DAC 2673
I will order a set of leads as well No reason to spend on Magnacor this time though...
08-30-2018, 04:37 AM
No reason to spend on Magnacor this time though...