for compression testing what do I do about the dangling a/c compressor belt? When I turn over the engine is that going to be a problem?

Seems like I need to turn the engine over to do a compression test and make sure the HT wires are carrying spark to the plugs in the first place.

 

It wasn't for me. I just sat the compressor forward, allowed the belt to just free hang on its own. The belt is so rigid, that it didn't pose a problem. My car wasn't running when I bought it, and I got so caught up in getting it running, that I did the compression test, rewired my ignition harness, and then in a attempt to see if the car would even act like it would start, it DID! And I hadn't put the compressor back in its place.

 

My car had a butcher instead of a mechanic. And it acted like it was out of time. Yet, in the end, it had a couple of minor problems, that someone made much much worse, by changing parts, rather than diagnosing the problem. When the plugs are out, the engine will turn over very freely. I put both coil wires near metal, and then turned it over. It was during these tests, that I found out it would fire on both banks for about 3-6 seconds, and then B bank would drop out. Rear "sensor" problem. Thats a whole 'nother story though. First things first.....

 

When you say coil wires- you mean the two central HT lines coming out of (or into) the rotor cap right? One is vertically taller than the other?

Greg in France had mentioned testing this too.

You literally attach the central lines to where they originated (the coil I presume- I took pictures before I took them off) and then crank the engine while holding one at at time near metal in the engine and see if there is spark?

I want to make sure I get this real right so I don't blow myself up.

 

Lol!! I doub't you'll blow yourself up, but make sure you don't shocked! The Marelli is a very potent ignition system. But yes, place the wires anywhere near metal (I did one at a time, and it fooled me), but when I did both, I clearly saw that both banks fired really well at first, and then B bank would drop out. But keep in mind, the Marelli was only designed for a .025 gap on the plugs. The spark will jump 1/2" or so, but its possible to short the rotor while doing this. So make sure you inspect the rotor really well, and then put the silicone under it at a minimum after doing this. The rotoir is nothing more than the pathway from coil to plug. This system makes much more sense the more you study on it.

 

my understanding was the electricity came from the coil to the rotor out the distributor wires to the spark plugs. Is that right?

I thought I was supposed to take the two plug wires that would normally plug into the two central locations on the distributor and put them near metal instead of plugged into the distributor to test for spark. Is that right?

I ordered a new distributor gasket and it won't be here for a while so I was going to do this test tonight or tomorrow night but it can certainly wait if I need the distributor reassembled.

My plan for the Marelli fix is actually going to begin tonight (or this weekend)- hopefully chronicled in pictures here-

https://www.jaguarforums.com/forum/x...js-v12-131142/

 

That is correct. You don't need the distributor at all to test for spark. Just put the coil wires from the coils, near metal, then turn the engine over. It should put out a nice white/blue spark from each wire very consistantly.

 

So- I have loosened 11 plugs but plug 2a won't budge. I have soaked them all in penetrating oil for a couple of days. I am afraid I am starting to strip the plug head with the removal tool that came with the car now.

Any ideas/ thoughts as to how to get the last plug loose without totally stripping it?

 

No good ideas. What condition are the other plugs in? If they look good it may not be worth removing the last plug. If it has to come out, you can try putting a socket on the plug that will bottom out on the hex, and hammer on it a bit to try to break the plug loose from the head. I do not know if there is room for a thread insert on the Jag head, I never needed to find out, but on most engines, you can put in a thread insert when the plug threads pull out.

 

Put a longish extension on the plug socket, ensure it is 100% straight on the plug, a long lever on the extension and undo. It will come out OK with a big click, but you will have to use some effort, or an even longer lever. Do not leave the plug in there. I strongly advise you do NOT hammer anything, the chances of shattering the ceramic and generally making things worse are huge. I change my plugs every year, and they are still sods to get out. Far more important re: stripping threads is to remember that the new plugs go in finger tight plus AT MOST 1/12th of a turn. They are taper seats, not compression washer plugs. Even an engine with finger tight plugs will run perfectly.

greg

 

will do with the wrench/ socket/ socket extension.

on another front I have vacuumed and sprayed out the recessions surrounding the spark plugs.

Does this look clean enough to remove the plugs, test compression, and install the new plugs (once I get the last one out)?

 

I don't worry so much about "clean" as I do loose debris. If you have a compressed air supply, its usually very safe to just blow away all dirt, debris with plugs in, before removing them. Whatever you do, get that plug out! No telling how long it has been in there. Plugs gaps increase over time, use. As you may realize, this seems to be a primary cause of the Marelli meltdown.

I may sound like a broken record, but I have had the misfortune of having two V12s drop a valve seat, totally unrelated to my ownership. Neither car did I know the ultimate history of, so no idea of its overall condition, other than how it looked. A compression test will let you know a lot about the condition of the engine. The compression testor, only has to be hand tightened to work. Has a o-ring on it to seal against the head. One lister was correct. These plugs are tapered. They barely need tightening. But I always put anti-seize on them, going back, just to make next time easy. Change the plugs every 10K or so, and I doubt you'll ever have the Marelli meltdown. All that seems to happen, is the plugs are neglected, and the path of travel of fire to ground (resistance) becomes so great, that going through the rotor becomes the path of least resistance. Once a bank of plugs quit getting fire, and the Lucas keeps sending fuel, well, you get the fire.

 

Once I get this plug out let's assume there is spark from the coils. Let's assume the compression test is good and let's also assume the car still won't start.

Is it practical to put everything I have taken apart so far back together before I attempt to check the fuel injectors/ possibly take off and clean the fuel rail/ injectors?

I would like to put something back together for a little confidence but not if I just will need to take it off again if I need to get the injectors/ fuel rail off.

Currently the throttle pedestal is off, the cruise control bellows is off, and the a/c compressor is off.

 

I think it would be better to advance in small steps and be sure about each one. As you know, I do not believe the CT is necessary, but new plugs certainly are, and a CT can do no harm. In my view, even if you had an iffy CT, it would change nothing as i believe it would only prove the engine needs a work out to loosen rings etc etc.So get the CT done and put in new plugs (gapped to 25 thou) and do not worry if the CT is iffy except if there is NO compression AT ALL on a cylinder.

Then put everything back together, very sensible, and easy to remove again if needed. Like you I am a great believer in not letting projects get out of hand and mind. Then:

• test the fuel delivery to the fuel rail (post again if you are not sure what to do), then (even if delivery is good)
• clean out the sump tank and change the filter and the main filter after the pump
• test an injector for working properly (ditto), then
• test for a good spark (ditto)

Then have fun driving the car after having done the brakes, changed all the fluids, etc etc !

Greg

 

for testing spark are these the coils? I basically attach an HT line to each and have someone crank the car while I hold them with some insulated combo of gloves/ wrench and see if it creates a spark and inch or half inch from metal in the engine?

Sound like a plan?

 

The only reason I so strongly advise a CT, is because of the 0 compression issue a dropped valve seat/burnt valve can cause. Seems a real waste of time, to spend any more time or energy on a car that you really have no idea will run well at all, once you've put so much time and money into. A CT only takes about 20 minutes. You needed to pull the plugs anyway.

If you have decent compression on all cylinders, then there would HAVE to be much more confidence that time and money spent is well grounded in fact, not hope.

I don't recommend holding those coil wires at all. You can take a nylon wire tie, a wooden or plastic clothes pin, and put the exposed metal end of the wire very near about anything metal. For that matter, you could use a couple of the longer plug wires, push the metal end out through the boot, and just lay it on the plenums. Then, without any help, reach through the lowered window, and spin it over. You will see the result if it is firing. If it is, put it back together. For what its worth, I might try and start it then.

Looking back, this 6.0 I got running after only a 2-3? year sit, I would have saved a LOT of time had I just cleaned/tested the injectors first. It was really easy, once I figured out a system to do it. I had a extra electric fuel pump laying around. Had I been systematic, I might have had it running great in 2 hours, rather than messing with it 4-6 hours, only to be frustrated that it would only run on 7 cylinders.

 

So- there is spark from both coils.

Compression test-

Compression

1a 130 130
2a 130 130
3a 160 155
4a 140 140
5a 140 140
6a 150 150

1b 0 0
2b 150 150
3b 150 150
4b 140 140
5b 160 160
6b 150 150

So 1b has no compression on repeated tries.

The plugs all basically look like burned toast at the electrodes.

What is the procedure now? Definitely in the dark here.

 

Honour is due to superchargedtr6 ! I stand corrected.

Absolutely no compression on 1B is amazing. Sounds like a valve is stuck open. I have no idea what others would recommend, of if there is a way to unstick it easily. But, if not, this is what I would do:

Remove the intake manifold on B bank (or better still, remove them both as a unit, this is not a difficult job, believe it or not)
Remove the spark plugs
Remove the cam cover on B bank, then
Turn the engine over slowly and see what the valve stems and springs are doing on 1B.

You might just be lucky and a tap on a valve or levering the stem downwards might release something. If not it is a rather major head job. Let's see what superchargedtr6 thinks!

Greg

 

also- I have what I would consider almost certainly some "collateral damage" from me-

this is right at the firewall and looks to be attached to a small bellows or smaller version of the cruise control bellows-

anyone have ideas as to what this is and how I would go about trying to repair/ replace it?

 

the engine also sounds different when turning over with the compression tester on 1b. Hard to describe but not as much pulsing with each attempt to start.