Hello.

lve been going through my 1982 XJS V12 that has been sleeping for about a year and a half.

l am currently waiting on a fuel pump , filter and a few other bits before i can try and start it. l decided to do so some ''tests'' to make sure im ready. Car cranks, l checked spark, all good. l then decided to check the injectors by turning the car on and moving the throttle capstan to WOT quickly, i did that and got nothing. ls this normal, do the injectors need to be up to pressures and other circuits to ''cycle'' for them to pulse................................or do i need to start digging

l was also wondering if this throttle movement needs to be done by the foot, switch maybe?

Thanks AOI

 

Nope.

Ign ON, engine OFF, open the throttle, hand via the capstan, or boot via the pedal, the result is the same.

Your should hear the 12 "click", all as one, as the TPS opens.

It is a simple test to determine TPS talking TO the ECU, then ECU talking TO the Resistor Pack, Resistor Pack talking TO the Injectors.

My suggestions:

Ensure the TPS is plugged in fully.
There is 12v AT the Injectors, either side, it matters not for this. (Obviously Ign ON, Engine OFF). The ECU is the Earth path later in the event schematics.
The Resistor Pack multi pin plug, and socket, are CLEAN, and I mean CLEAN.
The ECU earth, alongside the battery is CLEAN, and again I mean CLEAN.

Your up there, and I am not, but here is a Pin Out for the HE ECU for the Aussie market. You may have all sorts of add on's, ours were very clean and basic, NO O2 sensors, NO feedback whatever, etc etc.

 

Many thanks for your input Grant. l will get on with this and report back...................................

 

Ensure the TPS is plugged in fully.

***l unplugged and cleaned, i could not get a signal to the switch, (the switch itself has variable Resistance) ...........i mean resistance, Resistance is the car itself ****

There is 12v AT the Injectors, either side, it matters not for this. (Obviously Ign ON, Engine OFF). The ECU is the Earth path later i the event schematics.

****l have no power to the injectors (have made a light and tested on both banks).****

The Resistor Pack multi pin plug, and socket, are CLEAN, and I mean CLEAN.

***Removed and cleaned.***

The ECU earth, alongside the battery is CLEAN, and again I mean CLEAN.

****Have cleaned 6 x earth points in engine bay and 3 x in boot. (method of cleaning, wire wheel/brush on all surfaces, then hit with contact cleaner)***

Nada, nothing sweet FA on doing it by hand . Something i did notice when cranking the motor there is a 'click' about the same time of the spark but not on every ''fire'' maybe 7-8 times out of 12

Any help most appreciated, BUT please be ''simple'' in the advice, as i am an electrical dullard

Cheers AOI

 

So, i was cranking the motor to measure the spark , the second crank (about 10 secs usually ) i had moved it up from about 25K to 27.5k had a couple of sparks and then nothing. Now, motor cranks, no spark (no clicks) no injector pulse.....................................i am doing well.

Cheers AOI

 

Not to hijack the thread but are you / where are you in BC (British Columbia?)

 

YAY, spark is back...............................Not 100% sure what did it, i found another earth (near the IA), cleaned that, disconnected the capacitor in the IA unit traced the coil and IA wires and very very gently pulled apart and cleaned connectors . l found 1 wire on a coil male that was connected between the female and plastic cover of the connector , one of the wires to the CTS that was a strand or two thick.................................one of those, or something i inadvertently nudged in the right place at the right time along the way, or the rain, or the wind or the dog farting.

Now we have spark jumping at 28k volts (maybe more, havent tried) but still no injector pulse when moving the capstan.

Cheers AOI

 

OK,

Doug's "fiddle factor" has kicked in.

PROVING

You have serious wiring issues in that engine bay.

Spark now is good.

CTS wiring being iffy, NOT GOOD. The CTS is teh PRIME signal for the V12 to run, as in "running V12, unplug the CTS = dead V12", its that simple.

No pulse is heading for an EFI loom that has degraded internally (COMMON), and is shorting to earth.

HOWEVER

The :Main: relay, in the RED socket in the boot, fires up all sorts of items, including the ECU, fuel pump, etc etc. It has 2 (TWO) #87 terminals. Make sure the wires have not "pushed out" of that socket.

AND

On the +ve battery cable, about 6" from the battery clamp, are 2 Brown wires inside a plastic cover. Make sure they are actually intact, as they be the POWER feed to those relays etc etc.

 

Repair using a new piece and connector the coil wire that was only a strand or two thick, and check all the others. Often the copper breaks inside the connector outer insulation.

 

Thanks Greg, sorry should have mentioned have already done these, did both the CTS ones for good measure. They where fixed before i tested and found the spark had returned.

Mark

 

Thanks Grant, i will get on with this and report back.

Cheers Mark

 

Life has the annoying habit of getting in the way of my hobbies.............fortunately rain has put a stop to this woodwork lark.

Back to the Jag. Well, i had spark and pulse a few days ago, i think they both came back at the same time but i didnt see it due to only checking for pulse at the capstan, however the capstan will/did NOT activate the injectors so i didn't notice until i plugged a light into the injector (ive read about this on another early HE car post #4 here https://forums.jag-lovers.com/t/xj-s...pulse/329234/4 )

Today i fitted the fuel pump went to start it and nothing, no spark, no injector pulse, gone. On wens it was firing and pulsing at regular intervals, i have done nothing to it since bar topping up the battery. So this is where im at now;

Fuel pump needs orange wire earthed to run pump (there was already a tail earthed there, someone has done it before)

Car turns over as it should

No spark

No pulse

12.7v at coils ign on all connections in place.

No relay click from front left behind headlight area relay


...................HELP, its a tossup between what i hate most at the moment, woodwork or electrickery.

Thankyouverymuch AOI

 

My priority for a few hours is to find and FIX a door rattle in "Her Highness's" X200 S Type.

I will give this some thought as I bash the S Type into submission.

BUT

Ignition, SPARK, and EFI Pulse are 2 issues.

The only communication of the "spark" system, TO the Fuel ECU, is the well talked "Shielded Wire" to pin #18 of the ECU from the Ign Amp.

 

Thanks Grant.

.............i may be worth mentioning.

Now i have something to reflect on, i think before i had sporadic spark and pulse, then spark and pulse, but now. nothing not a single click.

lt has also rained, a lot, i have a little water thats coming in on the passenger side. maybe down the inside corner of the firewall.

l realized i have cleaned in the VEE area abet gently as gently can be, and ive squirted a tiny bit of PT blaster in the spark plug reccess in prep for new plugs.

How do i isolate and check that wire of doom?

Cheers Mark.

 

OK, all sorted.

Loss of spark is a seperate issue to the pulse, mainly.

SO:

1) ALL the wires related to the coils, the one in the V, and the one out the front of the radiator need to be verified as GOOD. For the patch loom TO the front coil a simple OHMS continuity test is easy, with the wires disconnected at each coil.

2) Ign 12v at the coil +ve terminal of the coil in the V, Ign ON, engine OFF. Then, with the meter still attached, go to "start", and observe the voltage drop is minimal, about 1v or so.

3) If test #2 sees a huge drop of volts, then apart from wiring issues, I suspect the Ignition Switch electrical section is is dire need of a clean internally.

4) Exiting the distributor casing, facing forward, and near the bottom, is a rubber grommet with 2 wires. These 2 wires are known to break INSIDE that grommet, and fiddling with the wires SOMETIMES reinstates signal to the AB14 Amp, and spark will return, until the next vibration kills the circuit.

5) INSIDE that AB14 amp, is the module (Brain), and screwed into one corner is a small cylindrical condensor thing. Remove this item, and bin it. It was a noise suppressor????, and are known to "leak" to earth, and kill the Ignition system, sometime intermittently.

The Coax Wire:

It comes from the rear terminals of the AB14 amp, and travels around the rear of the engine, past the heater tap, and off into the RH inner guard area just in front of the RH door hinges.
It is a standard Coax cable, like old style TV antenna cable. The fine wire inside the White core breaks, or the White core breaks, and the outer braid shield makes contact with said wire, and earths it, oops.
Unplug the ECU loom, locate and probe pin #18, and using wire extensions, probe the other end in the engine bay. You must have continuity, or the beast is dead.

Again, the fiddle factor can reinstate signal, and the engine will be fine for ??????how long.

I read that the Orange wire has been bridged already, and the fact your car will have a 6CU ECU, is kind of normal now. The 6CU had issues with the fuel pump circuit, and that was a good fix, but care must be taken, as the pump will work whenever the Ignition is ON.

The 6CU can fail to signal the Injectors, even with the Coax intact, although it is rarish, it does happen, and the later 16CU is a plug and play replacement.

Dinner is up, I will return.

 

This pin out I scribed years ago has saved me hours of "what the hell", and to probe each connector and the other end in the engine bay is not that hard.

 

These may clear the mud a tad.

 

Many Many Thanks Grant,

l will have at it and report back.....................................firstly im going to remove and clean the ign switch (disassemble in clear plastic bag as per your advises) as that has just started displaying a little weirdness as in turn off and the buzzer stays on unless you jiggle the key or remove the key completely...................filthy i suspect.

lve resigned myself to a lot rewiring and was going to start from the bottom of the VEE outwards when i did the fuel system rubber part rebuild so those dizzy wires will be last thing i check.

.................................................. ........it will be them then

Cheers Mark

 

Mark
I want to emphasise Grant's last point in his post no. 15 above:
"The 6CU can fail to signal the Injectors, even with the Coax intact, although it is rarish, it does happen, and the later 16CU is a plug and play replacement."
The 16 Cu is a far better item and it is, as Grant stated, a direct no-changes-at-all-needed replacement for the 6 CU. So if you luck into one of them, it is well worth buying.

 

Amen


Good move; you're on the right track. "Just do it"

Others have given so much substance there's nothing I can add except emphasis.

Baked, brittle, degraded, rubbed-raw, corroded, and rotten-to-the-core wiring in the engine bay is virtually a given with these old V12s. Until you've taken the time to methodically seek out and repair the wiring faults any other diagnostic efforts will be more frustrating. Been there, done that, on two V12s of my own and a couple others along the way.

And,by the way, when you're working anywhere on the car, take a few minutes to clean and tighten any ground points you happen across. You've be preemptively solving most of the oft-ballyhooed "Lucas, Prince of Darkness" woes.


Cheers
DD