Hopefully I'm posting in the right place. I have no experience with forums so please bare with me. I have nowhere and no one to go to for info on this car and I'm hoping someone will be able to help out with some of this.

The majority of my experience is with American domestics, but I have dabbled in some Asian and European. However, this '84 XJS (H.E. (not sure what that designation is or means)) is a bit overwhelming to me, basically because the service information I have has been less than helpful with the operation of the systems and component testing.

The history of the vehicle as I know it:

The owner purchased the car 7 years ago from the original owner or at least they owned it for the majority of its life. It was well maintained, stored inside and never seen snow. After he purchased it, he drove it to storage and it stayed inside until the following year. He took it for a test drive the following year and parked it for another year. The storage unit closed up and he had to move it. When he went to move it it wouldn't start(5 years ago). Over the last 5 years it has been to several shops, "mechanics" and at one point was stored outside at his friends lot for a year or two. Nobody has been able to get it running. (Just a little side note: One shop it was at is probably the best shop around us. They have a great reputation and work on a lot of foreign cars so it baffles me they couldn't handle this). I picked the car up a few weeks ago from someone I don't even think I could consider a "back yard mechanic". He charged the owner $1000 and all he did was put a battery in it over the course of the 1 or 2 years he had it and said it will run on starting fluid.

My diag so far:

I checked the oil and it looked clean and right where it needed to be so I tried starting it a few times with no success. I checked voltage at the fuel pump and it had battery voltage and the pump did run. I also looked at the wiring around the pump to the battery and relays in trunk area and also the connector that is plugged into the battery cable. I'm only bringing this up because there is a chance I may have inadvertently "fixed" a connection that wasn't working before. So after that I put a 10A charger on the battery(the battery didn't seem low and it was brand new, but I though it would be a good idea) while I contemplated my next step. I then disconnected an injector and hooked a noid light to the harness and also disconnected a spark plug wire off another cylinder and hooked up a spark tester. I went to crank it over and the thing fired right up and seemed fine. (One more side note-I assume there were chipmunks or mice in the engine compartment at some point during it's stint outside because of the acorns under the hood and on the intake. However, I haven't noticed any nests, feces or chewed wires so it may have just been left under a tree with the hood open. I just can't rule out chewed wires yet.) I let it run for a minute until I noticed some smoke from old oil and acorns and junk on the engine so I shut it off. I tried restarting it and it fired back up so I shut it off and clean all my tools off it so I could pull it outside. Opened the garage door to move it out and it was dead again. It would only crank. I rechecked everything, still had fuel pump, spark and injector pulse. I tried starting fluid in the intakes and it will start very quickly and run for a second or 3 and then dies. So I noticed that it seems to crank fast for a revolution or two then it seems audibly slower. I hooked my voltmeter to the battery and it drops to the neighborhood of 10V cranking, that seemed low. I thought maybe the low voltage might affect the computer so I hooked up a new marine battery that I had. It doesn't drop as much now, but it still runs off starting fluid so I have a hard time justifying the low voltage as a problem. Ultimately I think the starter may be an issue too although I don't think it's a main issue and I think I have to put it on the hoist to do a started draw test. In addition to that, there are a few electrical issues that I can't rule out as a related symptom. 1)The radio doesn't work at all(I don't think this is relevant). 2) The "Trip computer" above the radio doesn't work and is sometimes off and sometimes displays weird characters. 3)The heater worked on initial startup and then at one point was only cold and then at different times would only work on defrost and other settings were dead(as of current it has been working great on all settings and near as I can tell other than a long delay on "Auto" which may be normal, but I don't know). 4) And the last was the buzzer. On the second startup the buzzer stayed on and it wouldn't shut off even with the key out and the doors shut. It didn't stop until I hooked up a bigger charger and it has been working fine since. Ultimately, I feel I need to trace down the battery positive wire an make sure I have clean connections to everything, but I still don't know if thats really the first direction I need to go right now. That was the first day and I left the battery charge overnight.
The next day I managed to get it running again and pulled it outside. It ran smoke free after the initial burn off of junk. I noticed it start to get hot and I had to snap the throttle to get it back down so I figured the thermostat was sticking. I took it for a ride down the driveway and lost oil pressure, the light came on. The oil was about a 1/2 quart low and the coolant cap on the surge tank was leaking. I went to the auto store and grabbed some thermostats, antifreeze, coolant cap and oil. The car had been sitting for about an hour cooling off and now the oil level was fine so I assume it just holds about a 1/2 quart in the upper part of the motor while its running but don't know for sure. I added the quart I bought topped off the coolant and changed the cap and it started up with good oil pressure. After further research I found it had 2 coolant caps so after topping the system off I ended up using about 6 quarts of coolant. Since then it hasn't overheated or lost oil pressure. So I returned the thermostats. I verified with a thermo camera and it seems to be about 180 degrees F so I think I have that taken care of and it hold pressure. I've also ran it for several hours and burned through all the old fuel and put in 10 gallons of new fuel, although it's the cheap stuff. Should it have premium?

Where I'm at now:

I can start it every time now. When its hot it starts perfect. When its cold I have to snap the throttle VERY QUICKLY about 1/4 to 1/2 throttle 1-2 times a second for about 30 seconds to a minute and then is seems to run fine. I can't test drive it cause it doesn't have plates or insurance and the owner won't be doing that until the snow is gone. So I'm storing this for a few months. The other thing is the exhaust doesn't smell right to me. It's not like rich excessive gas smell it just doesn't smell right. Maybe it's just that engine, I don't know.

I want to check fuel pressure but I'm waiting on parts. I did try to check with a cobbled set up that leaked and I measured 40psi between the right regulator and fuel rail. I ordered a hose that I can cut up to insert a test port but I won't have it until next week.

The coolant temp sensor appears to have the correct resistance values in relation to temp so I don't think thats an issue

The air temp sensor is reading 3k and it looks like it should be 300 ohm at about 65 degrees F so I think I'll order that tomorrow. With that, the terminals in the sensor are pushed to the side and do not even go in the harness so the computer isn't even reading it. They are very stiff terminals so I find it hard to believe that happened accidentally. I think they'll break if I try and bend them back. Another side note-the car idles about 1100. I put a 300 ohm resistor in place of the air temp sensor and the idle came down significantly, but it runs worse and doesn't seem to start any better. More to come on that I guess. Now that I'm rereading this and thinking about it-it runs rougher with the resistor, but its at a lower idle. Maybe a misfire? Maybe I couldn't notice the miss at higher idle. I'll have to check that better after I get the new sensor.

I guess I feel like theres a better systematic approach than checking every sensor and the entire power supply and electrical system for this car. I know theres some valve on the intake for idle/cold start, but I don't know if that can cause this. there is a bolt backed out of it that I assume someone was messing with. It also sounds like a vacuum leak maybe left side, but the air cleaners were installed wrong and now may just not be sealing up. I don't have a smoke machine, but feel like it may be worth the money to eliminate that system or possibly fix it. All thoughts, info and suggestions are welcome and much appreciated!!

Thank you in advance

 

Welcome to the Forums.

When you settle down, and have a beer, please do an Intro in the New Members Area, it keeps teh BOSS happy.

There are many stickies I have written at the TOP of this section.

Have a read. I have many more and will attach later if you need.

HE is High Efficiency. USA =11.5:1 comp ratio. The rest of us = 12.5:1 comp ratio.

DO NOT get carried away with oil level, its a 10+ ltr sump, so even a litre++ down will do NO harm to anything, unless there is OCD involved.

STALE fuel is my best guess, and grubby fuel filter, and so on.

Thermostats, BE CAREFUL, as most suppliers will supply the WRONG stats, dealer included.

I have attached my "thermostat fiasco" paper. It is CRITICAL that the correct length stats are fitted, NO flexibility here at all.
Bleeding that system CORRECTLY is also paramount.

When you have CLEANED all the gunk from the engine, and decide to start it., LET IT RUN, for 15 minutes or so. Starting and shutting down a V12 is bad news straight up.

BEFORE any of this, you have a LOT of cleaning, more cleaning, wiring testing, etc etc before running it. The cooling system sounds sad, due to sitting so long, and radiator OUT and Pro cleaned, and block and heater core flushed would be #1 on any list I would make. Overeheat a V12, your Bank Manager will luv ya.

 

Hi Ffirebug

That Bolt of which you were talking about sounds like the 'Hot Idle' adjustment on the AAV (auxiliary air valve) which needs to be adjusted when Hot to get the Tick over right abt 750 rpm

"I guess I feel like theres a better systematic approach than checking every sensor and the entire power supply and electrical system for this car. I know theres some valve on the intake for idle/cold start, but I don't know if that can cause this. there is a bolt backed out of it that I assume someone was messing with. It also sounds like a vacuum leak maybe left side, but the air cleaners were installed wrong and now may just not be sealing up. I don't have a smoke machine, but feel like it may be worth the money to eliminate that system or possibly fix it. All thoughts, info and suggestions are welcome and much appreciated!!"

 

I don't have time tonight to address everything in my original post, but I'll touch on a few things and my one major update. And I'll get to the rest in the next couple days hopefully.

1) The cooling system, currently, seems to be working fine after the new radiator cap isn't leaking. And after the coolant has been topped off and the air bled out. (The clean that was recommended I will tell the customer, but he seems a bit hesitant to spend any extra until it starts reliably. I completely understand after all the money he's spent with absolutely no return this far. So I'm trying not to push any repairs on him until a few other things are sorted out.

2) I've ran all the original fuel out of the tank and put another 10 gallons of fresh petrol in it. I don't know how much of the 10 i've burned through because either the sending unit isn't reporting right or it holds over 5 gallons before the gauge come off "E". Either way it's been on empty for some time now and it took over 5 gallons of the initial fill to get the gauge to move. If anyone can comment on this I'd appreciate it. That being said, I don't believe the fuel quality itself is a problem (maybe pressure, I'll comment on that later in the post).

So I started down some rabbit holes ignoring the fact that this thing starts with starting fluid which brings us to 3

3) I borrowed a smoke machine from work and smoked the engine.The only leak worth mentioning was from the idle bypass valve (not sure if thats the correct terminology) but I expected that since the engine was cold. And since it has been idling around 750-800 after I change the air temp sensor I don't believe it's worth checking hot. Oddly enough, I also found half a dozen vacuum lines that were deteriorating, cracked, sliced, oil soaked and obviously leaking, but i didn't notice it with the smoke-just dumb luck. So I fixed all those, but suspect there has to be many more that I couldn't get too. all the the other vacuum components didn't appear to leak.

4) The driver side fuel pressure regulator has evidence of fuel leakage into the vacuum hose. I haven't got it to leak when I could see it, but when I clean it and put it back on it's wet again when I check it. So I suspect thats a problem.

I've been tied up with other projects, hence the long delay between posts. I finally made up a fuel pressure test line and went to hook it up last night so I could move it out of the shop and no matter what I did I couldn't get it to start. No fuel pressure and the fuel pump won't run. I'm not sure if this is a new problem or the original problem, but it finally gave me somewhere to start. The fuel pump relay wasn't mount to the bracket and instead was hanging upside down. I unplugged the relay and it was coated with blue/green crusties or "battery poop" as the kids call it. I see no evidence of water intrusion so maybe it was from snow after opening the trunk, I don't know. Tried a new relay and still no go. So today I did some wire testing. The orange control wire from the computer wasn't grounding the relay. I checked the computer for powers and grounds and all was good. I was gonna give up but the beer was kicking in so I decided to take the computer apart since I've had issues with 80's vintage computers and solder joints. I noticed a cracked solder joint on pin 1 which is the computer ground. So I had someone turn the key on while I had the disassembled computer hooked up in the trunk. When the main relay kicked on the pump still did not so I pushed the cracked solder joint with a probe and the pump kicked on!!!! I'm sooooo hoping this is the whole problem, but I'm still a bit skeptical. Anyway, I re-soldered that pin and several others that didn't look very good.....

So it seems to be running good right now.....time will tell. The fuel pressure is about 38psi right now, but I notice some times it holds pressure and other times it bleeds off fast. Not sure if this is the regulator or the recall of the fuel pump. More to come on that after some more testing.

I need help with this right now and I don't know if I should make a new post or just do it here so please advise me. There is a solder joint that looks like it should be bridged but its not. The gap is too close to be safe if it's not supposed to be bridged, but it's too far apart to think that is was recently separated and I suspect if it's supposed to be bridged it probably has been defective since it was new. I took pictures of it and I need to figure out how to upload them, but I was hoping that someone would be willing to take the cover off their ecm and see if the connection is bridged or separated. I just don't want to repair the solder joint and fry the computer without some confirmation. If I have to I'll get one from the junk yard but that could get pricey. Please, if someone is willing, let me know and I'll do whatever I can to figure this out

Zoom in on the black dot. Just above the dot you'll see the connection I'm talking about.
.

Overview picture (the black dot is just down and left of the MAP sensor)


This one is upside down for some reason but the dot is just up and right of center and the connection is just below it. This one is a bit blurry when you zoom but it's another angle to see it. the other photo is better.


Thanks again in advance!!