Well no mention of ignition timing. At idle it should be 0 deg with vacuum advance disconnected.

Also you need more than spark. fuel and rotation. You need a proper mixture, proper ignition timing and compression.

Have you done a proper compression and leak down test?

These systems are not that complicated. You just have to check everything. There are no fault codes to work from. So start with seeing if the engine is any good. Measure the sensors and check continuity on wiring for output devices. Verify the readings at the ECU connector.

 

Thank you Greg for further things to look into.

I know I am getting voltage to the ignition amplifier, but do not know how to test that nor the other parts either. I will search the forum and see what I can come up with and update this thread.

 

Greg Edge,

Looking into how to find the timing marks on this car - it is QUITE tight in the front.

I will check the compression - I know I thought about doing this when I was doing the spark plugs, but did not.

I am not sure if I am going to be able to afford all the additional manuals and diagnostic tools to get this thing going again. It is a pretty yard ornament though.

M.

 

I'm a bit reluctant to get involved here because any time I mention an engine component someone tells me this model doesn't have one.
Anyway we've established it has an engine and it starts fine and ticks over.
If the timing was out or the compression was bad it would be hard to start and wouldn't tick over.
It sounds to me as if the ECM is turning off the injectors as soon as it sees a throttle open signal from the TPS.
The scope will sort that (but not the reason). In the meanwhile what does the noid light do when you open the throttle?

The only other clue is the jumping speedo maybe due to low voltage.
I wonder what voltage the ECM is seeing (don't tell me, on this model it uses fluidic logic with no electronics, hence the vacuum line).
Do these ECMs get corrupted and need a hard reset sometimes?

 

Steven, it is obvious that you know nothing of Jaguars - these things run on smoke not electrical voltage ;-) (JUST KIDDING!)

Thanks for the thought about checking bat. voltage, as much as I have been working on this car with the trunk and doors open (and engine not running, I very well have could have run down the battery). Will check when I get home.

I know I had full charge last time I was dealing with this as I was reading voltages in the 12.7 range not running and 13.8-14 range when running (I think that was what it was).

M.

 

There MUST be mirrors involved as well.

The point about the noid light was that it should still flash as the engine dies
If it stops flashing as soon as you open the throttle that's what is killing the engine.

The XJ/XK models are notorious for getting electronically screwed up by low battery voltage - I end up sounding like an Indian PC call centre by suggesting a hard reset for any problem from a wheel falling off to the cabin filling with green smoke but have no idea if it works on your model.

 

From the way that your speed and odo are performing, I would suspect an earth problem, or an incorrect connection for speedo or tacho. Try checking earth lead from motor to chassis, and battery to chassis. Also the earth for the ignition module.

good luck

 

The vacuum line to the ECU is for the MAP sensor. The MAP (manifold absolute pressure) sensor is what the ECU uses to determine load along with throttle position.

Have you connected a vacuum gauge to the intake? If so what are the readings at idle. And what happens when you open the throttle?

As for diagnostic tools I think some of the junk auto parts retailers rent or loan them. Auto Zone, Advance auto, etc. I am not sure since I own all this stuff myself.

The timing mark is located from under the car not from the top. Makes it fun if you do not have a good timing light. The cheap one have short leads.

Bring cylinder 1A up to TDC on compression stroke. Then check that the mark on the balancer is at the zero mark on the timing pointer. Then remove the cap and make sure the rotor is pointing at cylinder 1A.

 

Guess #2 From a guy that doesn't currently have an XJS but does have a repair operation manual...

Engine Speed Sensor, located withing the distributor:
..."has two reed switches that are closed alternatively per one revolution of the crankshaft. Each switch triggers the ECU to produce the electrical pulse to the group of 6 injectors...From this signal engine speed is determined"

Could the switches have been intermittently working and finally failed?

Again, this forum is full of brilliant minds that can provide better guidance. Personally that sounds like the failure of a CPS (though your car doesn't have one). I am not sure what inputs go into the ECU and am ignorant to a lot of the inner workings of the v12.

As a random guess...is it possible to swap a distributor with somebody near by?

 

Reed switches? That is the old Opus system. The car in question has the Lucas CEI ignition. It uses a distributor pickup but it is not mechanical. It is a magnetic pickup. However the wiring could be suspect.

 

There you go - another thing this car doesn't have.
Could it be low water level in the boiler or the wrong sort of coal ?

 

Ahh yes, I was looking at the wrong insert.

More research yields that the following sensors serve as inputs to the ECU:

Manifold pressure sensor (internal to the ECU), Speed Sensor (derived from ignition pulses), Engine temperature sensor, Inlet air temperature sensor, and Throttle Potentiometer. These coupled with the battery voltage (OP did have some weird electrical behavior) ensure the correct fueling is maintained across all operating conditions.

...more thoughts from a noob

 

'Could it be low water level in the boiler or the wrong sort of coal ?'
I would tend to go for depleted dilithium crystals or possibly a short in the naquada generator.
Steve

 

As I see it, you have established more than once that there is spark, ignition, fuel pressure, no vacuum leak and ignition timing settings that should let the engine run easily in idle and also should easily pick up some more rpm without load. Small changes in the above parameters would not result in “sudden death” when applying some throttle, but rather rough and uneven running. There is also compression enough to make the engine idle and therefore more than enough compression to make the engine pick up some more rpm.

My bet is on ECU / Injector pulse

What happens if you disconnect the linkage between throttle turntable and butterflies and then slightly turn the throttle turntable without the butterflies connected? (Anyone, please warn me/us if this is not a wise thing to do).

If nothing happens, I would assume the ECU is not getting signal from the throttle turntable or the ECU itself is not working correct.

If the rpm is rising a bit, that would bee amazing, but also an indication of very lean idle mixture.

If “instant death”, we’re no further but again this could point to ECU.

Earlier in this tread, someone asked what happened with the injector pulse when applying throttle. I think this question is of major importance.

And please correct me if I’m way off with this. (I have not to much experience with V12 with injection).

 

This thread is getting long so yes, the question has been asked and the OP is waiting for an USB oscilloscope. The injector pulses should lenghten considerably as you start moving the throttle and continue to increase. As you settle at a higher RPM (e.g. 1500rpm) it should shorten again but still be a perceptibly higher than at idle. If you run this test wth the gear engaged and foot firmly on brake then the loading should give considerably longer pulses at 1500 rpm than if run in neutral/park.

EDIT: If the pulses disappear immediately you touch the throttle check ignition pulses as said previously. Absense of ignition pulses switches the injection off immediately to avoid flooding the engine.

 

Sorry for taking so long to repost - Jaguar is still but a lawn ornament.... No cables yet from the USB/Oscilloscope - I think this MIGHT show me what is lacking (if injectors are not providing fuel, then that WOULD provide this issue). Spark seems to be there (have put an inline spark tester off the dist. and shows that it continues to fire when the throttle is cracked open (but car dies suddenly).

The jumping speedo was due to a low battery (leaving the trunk and door open for hours sort of drains it down) - it was at 11.2. Cranked strong, but gave those weird anomalies. By charging the battery to full - these ghosts went away. This was definitely electrical related. (refreshed the smoke supply).

Anyone have a spare ignition amplifier and/or ECU laying around for me to test with (will pay for shipping back and forth).

Steve, you mentioned "hard reboot" - I was not aware (in quick searches on the forum) that this could be done (or were you referring to the PC fix problem?). If not - how would this be done on my car?

Thanks for all the guidance so far! We will get her humming along eventually.

M.

 

I only went back a couple of pages to your repost of everything you'd done so I may have missed the following:

You appear to have a good idle voltage at the TPS, but when you turn the throttle capstan, does the voltage rise smoothly? You can have voltage at both ends but "missing" a spot in the middle. Then, have you verified that this voltage is making it all the way back ot the ECU by checking for that voltage on the big-*** plug on the ECU? Your car seems to have everything pointing to a TPS issue.

Timing is actually set at 3000 rpm...I'm sure you can get a ballpark number at idle but proper factory set procedure is at 3000 rpm. As if cehcking the timing on these things wasn't enough of a giant pain in the ***. I think it's 18BTDC@3000. My car was almost 20 degrees retarded when I got it, and drove it for a year that way! Imagine the fantastic wakeup when I fixed that little issue!

D

 

Darel, TPS was very smooth from base to peak. No spikes or holes going up and down.

Cannot get the car past idle - so seeing 18 BTDC @ 3000 is not going to happen (yet). Will be seeing if my timing gun can find where I am.

M.

 

I am getting confused here. The relevant item is the TPS which is fixed under the throttle capstan and turned by the central spindle of the capstan engaging with the centre of the TPS. The microswitches on the outside of the capstan are nothing to do with the TPS. My car, being UK spec, does not even have any external microswitches on the capstan.

The OE kickdown switch on this model is on the throttle cable and is just before where the throttle cable is fixed to the capstan tower, at the point where the inner of the throttle cable emerges to wind round the capstan exterior.

 

See my reply above, which for some reason has come out on the thread before the post I am replying to!