Hey guys, worked on the 6.0 in the 94 XJ12 donor car today. I am wanting to swap this into my 89 XJS. I used a EFI pump today, bypassing the cars original fuel pump. The engine is exceptionally clean, has 122K miles on it, but been sitting awhile. When it started, it sounds great mechanically, but skipped badly.
First, pulling plug wires, one at a time, cylinders 3B, 5B, 1B, 1A, and 4A made no difference whatsoever in the way the car ran. So I changed the plugs. They were NGK BR6EF. They appeared to have been in the engine a long time, and most looked very fouled. Engine not burning clean at all. But when the car started, it didn't smoke in the least. No white smoke, no black smoke. I let it run for at least 20 minutes, and the car ran very cool. I could still actually put my hands on the intake manifolds, etc.
Anyway, I went to a local O'Riely's auto part. All they had in a set of 12, was Autolight 103, which was shown to be OEM plugs. They called for a .035 gap. Put the new plugs in, and couldn't tell a bit of difference in the way the car ran. So, compression check time. 1A 215lbs, 2A 235, 3A 220, 4A 230, 5A 230, 6A 230. Not too bad. B side much worse, 1B 140lbs, 2B 210, 3B 240, 4B 190, 5B 225, and 6B 140.
Obviously, my problem is more large than I hoped. 3B skipped, but had 240lbs of compression. 5B had 225 but skipped. 1B 140lbs, 1A 215, and 4A 230lbs. My thoughts were that with 140lbs, 6B wouldn't have made a difference when I pulled the plug wire, but it did.
My thoughts are that I have a combination of fuel delivery problems, along with low compression issues. Just loking for a common thought here. My next thought is to pull the manifolds, valve covers, and heck valve clearances, as well as test injectors. Any and all thoughts appreciated.
Again, this engine is extremely unmolested. After several hours of working on it, my hands were barely greasy. The engine is uncannily clean for its milage.

 

So the engine is still in the car? Inspect the wires and distributor

put a bit of oil in the low comp cylinders and see what they do

why is the car a donor car?

 

The car is a donor car, mainly because it was allowed to sit and completely ruin the paint. The interior isn't bad at all, but smells like it has been closed up for a few years. Very musty. But, caution to the wind. I went by the local store, looked at
marvel mystery oil, seafoam, all kinds of top end lubricant. But my
all time favorite for freeing things up, is PB Blaster. So, I
bought two large cans, and sprayed the cylinders liberally. Twice.
Turned the engine over a few times in between. We'll see tomorrow
what changes.....if anything. I am grasping for straws here, as
about the only thing else it can be, would be stuck rings, or
carbon caked valves. The plugs were very very nasty, like it had
been driven around by someone who was scared to let her rip every
now and then.

 

Oh, and the cap looks great. Its the heavy Marelli cap, with the brass inside. Not the cheap lightweights with aluminum. The wires look great. In fact, as I've said, the wiring, hoses, everything are very pliable. Nothing like my XJS V12s I've owned.

 

The plug gap should be .025". this is important to have right with the marrelli ignition.
The missing may be nothing more than sticking injectors, they tend to gum up after sitting for any length of time but can also free up with a little soaking and use. A test lead on those that are suspect will soon show if they are cycling or not.

 

Looking at my numbers, I feel absolutely certain I have 4 cylinders not getting fuel, as they have compression, are firing to the lead, and I put the new plugs in. The problem is 1B having 140, as well as 6B having the same. Regardless of fire, or fuel, that low of compression can't be good. On the other hand, with no fuel at all, and if the rings were stuck, that could be a problem too. Damage may be done. Anyway, tomorrow is a new day of discovery, and I will do another compression test after having the oil in the cylinders overnight.

 

I wouldn't be surprised if both the rings and injectors were stuck. That is a long time and the engine has enough **** in it to make them stick. Fuel just turns to gel and varnish nowadays so that could be an issues too...PB blaster will probably help. I love MMO but seafoam is pretty crap imo.

I would pull the injectors to inspect and clean them and during that time give it a week or so of cleaning/lubing and giving a few turn overs a day to see if the rings change.

 

I'm hoping against hope that this engine is suffering from long term sitting. I plan on checking the injectors alomg with trying to get the rings freed up. Wish me luck.....

 

I bet it is just injectors or some other electrical gemlin. Have faith!, Good luck.
Greg

 

I worked on the engine some more today, and have
maybe some good news. After soaking the top end in PB
blaster, I now have great compression on every cylinder. As
I started to check it, it started out as it was, but then
the gauge jumped up as though something did free up. I
started with 1B since it was my lowest. I also cleaned my
injectors. I had 4 not working at all. A 1.5V battery
wouldn't cause them to work, so I cycled them with a 9 volt,
and they all now work. I ran carb cleaner through them, and
it was pretty amazing to watch the difference in the spray
pattern as it was cycled with the cleaner, and then back to
gas.
So, I have good news for the moment, BUT....in my
disassemby, I noticed a small fiber washer on the valley. I
got to looking, and one of the green ''hats''?? on the
injector muct have come off, and went down into 3B cylinder.
I tried everything to see it, but it appears to have gone on
through. But I am now missing a part of a working injector....

 

Ok, with the help of Dave at Jaguarfuelinjectionservices, he kindly sent me my missing pintle cap. The engine started this evening. After burning off the penetrating oil, allowing it to get up to temp, I held it at 2000 rpm a bit, then revved it to 5-6K intermittently, then allowed it to idle a few, then revved pretty good some more. The engine doesn't some a bit, sounds really good above about 12-1500rpm. The engine has a definite even "miss" evenly. Meaning you can't tell one side from the other. It seems to run very very well, yet I know I wouldn't be happy with the semi-rough idle. You can put the car in gear, and feel it. Not smooth as silk, as a V12 should be. Not really "skipping", as it feels like it would run great, going down the road. I even put it in gear, and power braked it pretty good, maybe up to 2500rpm, and you can't feel any skip at all. But let it idle, and it can be felt. Rechecked all of my wires, everything looks great. New correct NGK plugs, of course new fuel in my makeshift pump/container/return line. Not sure what to do next, except pull all the plugs, do another compression test, or? Thoughts, ideas appreciated!

 

Sorry, didn't proof read. Doesn't smoke a bit, even under hard accelerations/de-accelerations.

 

Ok guys, I allowed it a 45 minute cool down, went back out and started it, and now I can't even feel a miss, although I hear vacuum leaking. I tried spraying it with carb cleaner, but no difference. I took the left hand manifold off to check valve clearances, but literally bolted the valve cover back on, as well as the intake without any new gaskets. O-rings on injectors looked, felt very brittle, rough feeling. I think I have a good engine here, but want to make sure before I go putting it in my XJS. If I need to do anything, I want to do it with the engine out.

 

Sounds like you got a good donor, and I'd wager for a great price!

Would you consider tallying the costs of this project and posting them for comparison (not argument LOL) with the costs of lumping?

 

This isn't a typical deal. All I can say is thank you, to David at Everyday XJ. I am sure lumping is a great idea. Really. Kinda always wanted a big block XJS. However, as I've gotten older, the V12 kinda grew on me. After rebuilding two V12s, the mystique is gone, and maybe foolishly, more confidence has set in. I simply like the V12. I can only say, don't buy one of these cars unless you can have some idea of its history. As many have pointed out, ONE TIME of running hot, puts you on notice. I put a lot of blood sweat, tears, and money into a inexpensive XJS, to have it drop a valve seat before I could put two tanks of gas in it. I may be crazy, but the desire to lump has gone. Dollar for dollar, I still feel you can repair the V12 for less than you can lump one. Keep it maintained, and I feel that one of these engines would run indefinitely. When I rebuilt the V12 in my then 71XKE, it was a total waste of money. Old engine, but the wear was nil. The exhaust valve stems were the only real problem other than the cracked valve seat.

Then again, lumping can be fun. Put a 302 Chevrolet in a TR6 once. Muncie 4 speed, Corvette diff with 4.09:1 gear set.......aghhhhh to be young and dumb again....

 

Well, it was hard fought battle, but I got the 6.0 out of the XJ12 this evening. Just FYI, I had to take the trans out first. The engine is a very very tight fit. Won't come out with exhaust on it either.
I did one more compression test on it after running it in for a bit, and I have one cylinder that is 190, 4B, but the rest have 230-240.

 

I didn't see mention of whether you took baxtor's advice to regap your plugs to 0.025, but, please make sure you do so. 0.035 is just too wide for these engines. 0.025 has always been the standard gap for both 5.3 and 6.0. Your idle will likely smooth out considerably after doing this.

 

Before taking the engine out, I went and bought the correct plugs, and did gap them to .025. The engine ran kinda rough at first, after pumping the top end with penetrating fluid, but after it cleared out, and then I let it get to operating temp, shut it down, did it again, several times, the engine was idling as smooth as I could ever hope for. I am still midly concerned with that one low cylinder, but not really wanting to go into the engine to find out why. I wonder what a leakdown test would tell me? Also, I have the intakes off, and plan on replacing the cam cover gaskets, so I plan on checking my valve clearances really good. I checked the first 3 cylinders on the B side, and they were really close. But conventional wisdom says I should run the exhaust valves a little loose. Like .016? and the intakes .012?

 

Afraid I am not a mechanic, and can't help with the valve clearances. Just popped in to offer encouragement and ask for some pics, please!

 

I think it was RGP who told us that in his experience all that setting the clearances bigger than factory spec does is make them clatter dreadfully with no other benefits!

I am 100% sure your clearances will be fine and no need to worry further. Ditto the cylinder that is a bit lower on compression. I am sure it will be fine and the engine just needs some work.
Greg