I got my XJS running with a new injector wiring harness. Thread about it here: https://www.jaguarforums.com/forum/x...stions-279460/

When I got it running, it was still idling rough and lacked power when I test drove it. The ignition warning light on the dash is on. I pulled the front six spark plugs (the easy to get to ones), cleaned and re-gapped them, and put them back in. After that it started easier, but still idled rough. I checked to see if the injectors were firing and got strong clicking on 11 out of 12. Good enough for right now. I decided to try a test drive, and it died in the driveway and would restart and almost immediately die. Since then, I've found that it starts when cold and then dies when it warms up. I thought it might be the ignition amp, since it's getting rather a lot warmer than the intake manifold it's sitting on, but after some searching here, I think that may be normal. It also has one connector that isn't hooked to anything, which I don't think is helping.

Where does this wire go?

Questions:
1. How do I test the ignition amp?
2. Does anyone have specs for the coils so I can test those?
3. Does anyone have an ignition wiring diagram for an '88? I have the diagrams for an '89, but those are Marelli ignition.
4. Any other ideas?

 

If that wire has a blue twist, it is the tacho signal.

 

Here goes.

11 out of 12, NOT GOOD ENOUGH by a country mile.
If the 6 sparks were sooty and gapped wrong, then the other 6 will also be knackered.
The HE will NOT burn sparks clean, no matter how much Italian you pour into the RH pedal.
Sooted (not sparking) sparkere will heat up that Amp and the Coils something fierce.

It runs, so leave the wiring alone for now.

The CTS (Coolant Temp Sensor), and its associated wiring, located on the rear of the B Bank thermostat housing, is a known issue as these beasts rise to operating temp. The CTS is CHEAP, and NOT unique to Jaguar, GM, BMW, Merc, SAAB, etc etc all use the same Bosch unit.

Check the integrity of your TPS, as it opnes from Idle to WOT. MUST BE smooth with NO lumps and bumps. You WILL need an old style Anolague/needle meter for this. Digital, maybe, but the damping in them is usually masking what you are trying to see.

Ign Light ON. Not sure on your market, but on mine that is generally the Aternator not playing games.

The fact it runs, is worth at least 3 beers, 1 for you, 1 for Greg, 1 for me, haha, get some Aussie in ya.

There is more, but this is the bare basics.

ONE MORE.

Check the engine to chassis earth strap. The factory THING is rubbish, so a dedicated strap, engine to chassis is needed.

 

You guys are onto something. I didn't have a lot of time to mess with it today, but I did manage to check the resistance on the CTS at room temperature and after a partial warmup. I got 2.7 kOhm at room temp and .33 after about a mile drive. This jives with the table in the 81-88 engine performance guide. I think the sensor itself is fine. However. this is how the wiring to it looks:

This wiring be no more good.
I think this may be part of my problem.

The car felt more powerful than before I did the front six plugs, which tells me I need to do the other six. I can also smell unburned fuel in the exhaust, which tells me more of the same thing.

As for the CTS wiring, should I just strip it back to where it's good and splice on a new end, or replace the whole harness? I traced it back to where it joins a big harness near the firewall that also has a lot of wiring that's seen better days.

 

That is so sad, BUT, so common these days as age creeps in.

I would work on that wiring with a new connector, and CAREFULLY open the mini loom as it travels back to the rear.
There is a solder joint, part way, where the ATS joins the party, then more splicing at the rear on the chassis side of the TPS loom plug.

Most I have delved into have had dried spaghetti for wiring back there.
It is the hottest part of the engine bay after all.

Being up there, you got cats, and they no like raw fuel, oops. We NO got them, luckily.

Always an adventure, until you have done it all, then repeat in 20 years.

 

I agree with Grant, strip it back to where the insulation on the wires is flexible. I redid mine about a year ago, and only had to doo about a foot of the wire. Buy new EV1 connectors and all good.

 

AND,

ONE wire at a time.

You do mot want to mess up ATS or CTS circuits, trust us.
Easy to do, I know.

 

It turns out the coolant temperature sensor is bad. I took my chances and drove it the 3.3 miles to work on Monday. It did well enough that I decided to try to take it to the car wash. It died in the street in front of my driveway, and I went in and got my multimeter. The CTS was open. A new one is on order from Moss and I picked up an EV1 connector with a pigtail on it from O'Reilly's today. Wrenching resumes this weekend, or possibly sooner if I'm feeling motivated.

Unrelated: Does anybody happen to know where I can get a manual transmission for a '77 Mercedes 240D? My other car is being a schweinhund.

 

Update: BROWN IS DOWN!

My coolant temperature sensor was supposed to be here yesterday. According to tracking, it went into a UPS facility on Wednesday and hasn't been seen since. I also checked the intake air temperature sensor and found it was bad, so I ordered that. I'm now a little surprised it was even running. I cleaned and re-gapped plugs until I found a really nasty one and then decided to just replace the last four.

Old plugs.
The really nasty one was 6A.

 

Replace them all!

 

This might be a video worth watching for you.

 

I got the coolant and air temperature sensors in today. The new air temperature sensor ohmed at about 2 kohm at room temperature, same as the old one. I thought it was supposed to be something like 400 ohms at room temperature. When I stripped the outer insulation off the wiring harness for the CTS, it actually wasn't that bad, but the connector was missing the wire, so I replaced that. It fired up with some difficulty and still doesn't run right. Rough running, lacks power, pings under some speed and load combinations. I took some video of how it went.
It also managed to stall after idling for a few minutes when I put it in Drive. I let it sit a few and then it restarted. I have my aux fan on a manual switch and I found that by leaving that on it didn't try to stall during a roughly 15 minute test drive.

I've seen Adam's video about the 15 minute Jaguar and I haven't looked at that sensor specifically yet. I did have the distributor cap off last week and while you can tell it isn't new, it didn't look obviously bad. I also ohmed the coils and got about .75 ohm on the low side for both of them. Testing the main coil from the high side to either of the low side terminals was 5.4 kohm. I back probed the voltage on the red wire for the throttle position sensor and got between .75 and 4.5 volts depending on position. This was with the key on and the battery on a tender.

I know it was suggested that I should change the other eight spark plugs. What should I look at next?

 

US cars don't have a 15 minute timer. That was a Europe spec thing. US have a 45 second timer. A description of the system is in Kirby Palm's Book.

 

Robert, if you want the car to work as it should, you MUST work through each system and put it 100% right. If you do not renew all the plugs forget seriously getting the car right. Ditto HT leads, dizzy cap and rotor.
Then there is the state of the injector loom, what is it like? Then the adjustment of the throttles and the TPS under the capstan, which should be set to 0.32v at throttle closed and 5v or near it at WOT, your readings above mean nothing. Then the fuel system, is it clean, are the FPRs working right? Is the sump tank clean? Are the injectors spraying correctly, is a cat partially blocked?
The car is ticking over OK with the aircon on manual because that is triggering extra air through the air valve on the A bank airbox, this is an anti-stall device when the car is ticking over, aircon compressor on. This is disguising the real problem.

There will not be one thing to find and then it will go properly. Why not have a good think about whether you really want the car to be 100% and if you feel motivated to do the work. This sort of grief is not for everyone, and why should it be!!

 

Likely correct but I need more specific information than that.

I replaced the plugs, plug wires, and distributor cap in June 2020. Since then the car has done 8000 miles at most. I wasn't able to find a rotor at that time, so I left the old one in. That being said, I just ordered a new cap and rotor from Moss. I also picked up another eight spark plugs from O'Reilly today. I don't think they're the cause of my immediate problem, but I can eliminate that possibility. I also picked up an ignition control module because I think that's likely the cause of my immediate problem. It was also really cheap.

Brand new as of 28 April.

I disagree. The .75 was at the idle setting. That's wrong and I'll add that adjustment to my to-do list.

All excellent questions. I typically work on this thing for a few hours once or twice a week, so the answers might take a while.

Wait, what? The AC compressor went in the scrap bin three years ago. I have the climate control set to "off". As I understand it, the extra air valve isn't supposed to be open at idle in Park or Neutral. Do you think it's opening when it shouldn't?

I know there are likely a few things (or more) going wrong. I'll be quite happy if I can get it running as well as it did before I left to go on deployment last year. I left the car in the care of an alleged mechanic shop and I got it back a year and a half and $3900 later running on four cylinders and with various other things like the turn signals and the horn no longer working when they did before. I've also considered selling it and getting something in better condition. I'm holding off on making that decision until I get my other car back. The transmission for it got ordered today, but it has to ship from Germany.

 

"I disagree. The .75 was at the idle setting." OK, but yiour original post did not seems to explain that. Good news on your other improvements. Good luck.