Dear friends...please I need some help and encouragement.

I have a XJS 1989 v12 convertible once running nicely.
Some time, after fixing a lot of worn things it started to start quite badly. Often I had to support the startup phase with hitting the gas. Once warm it was running smooth. But day after day it got worse. So I started searching, cleaned the sump tank, got a new pump and filter, put new ditributor and lead set in... but it did not get better. It became even worse... I did not start any more at all. Your always heared some ignitions, but not sufficient to start up the engine. So I started to investigate the loom and found... the TDC had been crimped and the plug had been cut away. The crimp was really bad, I had the loose cable in my hand. So I was sure having found the fault and repaired that. From that point the engine never ever made just one ignition. It just cranks and cranks. At his point I was always able to see the tachometer showing revs, but tody this is gone, too.

So what have I done the last 72 hours:
- I checked for fuel injection - this runs fine (you see it at the first injectors and you smell it from the exhaust meanwhile)
- I checked spark either at a single spark or at both coils directly at their output - no sparks, nothing
- I ckecked for 12V at the white cable at the ignition boosters, at the coils and at the Magneti Marelli Ucc Pin: ignition feed 12V is fine
- I swapped both, the TDC and the ESS, reseated them an prooved theier position - no difference
- I measured TDC and ESS resistance at the MM ECU - both are fine there
- I measured the connection from pin1 of the ignition boosters to theier coils - both are fine and they are not mixed up
- I replaced both ignition boosters - no difference
- I checked the ECU for soldering or shorting damage - looks nicely
- I swapped against a second MM ECU - no difference
- I checked engine grounds and MM ECU ground - absolutely top

So far - here I am stuck.
No idea and highly frustrated. The only chance I see is to start looking with my osci now.

Do you have any ideas and hints?

Thanks friends...
Tom

 

I would go back to what worn things you replaced first off. Look at those things only, since that is when your problem started. I suggest that it is something like I would do- as simple as a wire left off somewhere, or maybe a vacuum line unhooked. Good luck, im sure there will be a better suggestion soon.

 

No spark isssssues...
please define ESS and TDC... I'm sorry, either I don't know or my brain is asleep - both happen often.

Completely unplug coil plugs from coils. First, check the tangs down inside the female plug receptors on each coil. Make sure the metal male tang didn't get bent and NOT making it into the plug.... Also, carefully check the integrity of the coil plus themselves. They can get tricky.

Remove the coil plugs, note which is which if possible - makes life easier later. Start cutting back the tape of the ignition loom where the coil wires separate out and go under the fuel rail to the coils. Dig into that area of the loom in both directions. towards the front of the car and back towards the firewall... You may find a problem there. You'll know it when/if you see it. If all looks well - a simple matter of taping it back up... There is a connection/junction where 5 or 6 wires come together in a (usually) very sloppy junction. All of it feeds ignition related stuff.

I'm saying this because you say you have no spark...

Also, please make a list of what worn items you've changed. That might give some hints.

 

Dear lucky drivers...
thanks for your ideas!
TDC - top dead center (crankshaft pulley), ESS - engine speed sensor (flywheel)

Did swap the coils and made one new 3-wire-plug for one just for fun, swapped one coil to a new one - nothing changed. Just cranking.

Did not want to open all of the loom - thus measured all pins from the Magneti Marelli Plug:
pin 1,2 - TDC, 633 ohm, no shortage to any other pins, fine
pin 3,16 - ESS, 730 ohm, no shortage to other pins, fine
pin 4 and 12 - ground - 0,3 ohm to chassis, fine
pin 5,18 - idle switch, 1 ohm closed (okay, could be better...) and endless if open, no other shortage, fine
pin 6,19 - coolant temprature, was 2,3 kohm, no shortage to other pins, fine with 20 degree Celsius in my garage
pin 9,10 - firings for power module B - no shortage, going through, fine
pin 13 - ignition feed, 12V with ignition on, goes to 2x power module and 2x coils... arrives all there, fine
pin 14,15 - firings for power module A - no shortage, going through, fine
pin 17,18 - strategy selection link, is open, no other shortage, fine
pin 20,21 - diagnostic socket, all open, no shortage, fine
pin 23,5 - air temp. swith, open, no shortage, fine
pin 24 - Lucas EFI link, no shortage, did not check to EFI, but injection works

Normally I should have a spark... shouldn´t I?
Unbelieveable...
Maybe the ESS is not deep enough to the flywheel. I had some problem reassembling these metal brackets.

Tom

 

Hi Tom

It sounds as if the Crank Position Sensor could be your problem, its on the Front of the Engine just under the Flywheel and should have a maximum gap of 0.042 or a bit less or the ECU won't be triggered and the Engine won't Start

So go and adjust the Gap on the Crank Position Sensor and hopefully you will get a Spark and the Engine will Start, where to support this Theory the Tacho Needle doesn't flicker when you Crank it like it did before

Good Luck

Alex

 

Okay, thanks for helping and encouraging me - I am proceeding...!
Have a spark again.
First I fixed the clearance of the ESS as I painted the aluminium bracket where the sensor to the flywhell sits and I measured about more than 0.048. It had bee maybe 0.06 or so. But this did not give success.
Second I realized that I disconnected one coil and the MM ECU for measuring those wires in the harness. But this did not succeed as well.
Third I wanted to see the gap of the TDC... it seemd fine... BUT I realized, that I put a new sensor in and connected this new sensor... but mounted the old one again...
I see, I am the problem.
Now it cranks and maybe all 2-3 Seconds it gives some ignitions, but it does not start. I am back here.
I found that I am getting nice sparks off the coils but not at the plugs. So I will look closer at the new distributor and rotor.

Have a good Sunday,
Tom

 

Dear friends,
I do not get the machine starting.
Inspected rotor and distributor. Have a new lead set intalled. Checked timing and movement of rotor.
Have fuel on all 12 injectors. Tried with open throttle as I thought it might not become enough air.
Checked Grant Francis PDF. If cranking the batery voltage at the coils goes down from 12.4 to 10.2 - but I assume this is normal.
I am really without any ideas now...
The only thing I have done before it begun that badly: I removed the auxiliary air pump. I did not remove all the hoses and pipes, but closed the vacuum line and tried with open/closed. But I am unable to find any correlation here...
If you have any idea... please.
Tom

 

While brushing my teeth some more thoughts:
As I am quite sure, that I have spark at the right moment and that I have enough fuel...
... is it possible, for what reason however, I´m not getting enough air into my engine?

I mean, it always started badly when cold. I always had to support with open throttle. Maybe the aux air pump delivered fairly sufficient more air to get it started and now, without this pump I´m lost?
Compression was not that bad, but not exceeding 10.5 bar. Maybe already a sign of lacking air?

 

You are a far better troubleshooter than I am. I envy and honor you. Don't give up. The solution is tight at your finger tips.

If you think that air might be an issue, what happens if while cranking you hold the peddle partly open? I think, IF the engine seems more willing to fire while cold, it can lead you to confirming or negating that as a part O the problem.

If you know you are getting fuel to the cylinders, it sounds like a spark problem.

Maybe this has been answered before, but WHERE is the wiring for the fuel injector loom?

Are you sure you're CPSensor and Flywheel sensor are mounted correctly and properly seated?

Are you sure that the little vac hose that runs off the back of the RH Intake to the Marelli ECU is in tact? It's orange plastic. And important. The ECU is in the RH foot well behind a kick panel.

Are you sure that the large vac tub that runs off the back of the balance pipe (near the fire wall) to the fueling ECU is connected and HOLDS vacuum?

Are you sure that the Throttle Position Sensor is set correctly to .32 to .36 V?

Then again, that strange connecting point of allllll of the wiring that powers ignition and runs to coils I mentioned. I'm sure that if I used a meter to check for continuity I would have GOTTEN continuity... But still, the wires were so corroded and the connection so poor - the car would run BIT terribly. The tachometer was allllll over the place. Often I was running on 6 cylinders BUT there was continuity in the wiring loom to all components involved. I'd say check with EYEBALLS.

Keep it up. You're close.

 

Hi Jay,
I am appreciating your help - thank you!

> ...what happens if while cranking you hold the peddle partly open?
Two months ago, that was the method to get it running, but it went worse week by week. Today there is no difference, either with pedal down or not - it does not start, just cranks, but gives a very brief fire up all 5 seconds. No chance, to get it running.

>... If you know you are getting fuel to the cylinders, it sounds like a spark problem.
These were my thoughts, too. And that´s why, I replaced already cable, rotor and distributor, tested the gap of all sparks. Swapped the coils and the amplifiers from a donor car I have here. Checked the loom and the 12V at coils and amplifiers.

>...but WHERE is the wiring for the fuel injector loom?
I made this one new a couple of months ago. But double checked by installing the old one for a test. No success.

>...sure you're CPSensor and Flywheel sensor are mounted correctly and properly seated?
I will triple check that, but yes, I am afraid they are sitting correctly. As well, here I swapped for the ones from my donor car. In deed, they could be defective as well, but this is very unlikely. Maybe I will check with osci tonight.

>...little vac hose that runs off the back of the RH Intake to the Marelli ECU is in tact?
>...vac tub that runs off the back of the balance pipe... to the fueling ECU is connected and HOLDS vacuum?
Quite sure, but will check that. Nevertheless I do not think that prevents the car from a start up.

>...ECU is in the RH foot well behind a kick panel.
Opened that, looked for damage. Nothing. Swapped with my donor car. Same effect.

>...Throttle Position Sensor is set correctly to .32 to .36 V?
Yes, it has 0.28V being closed. Tested even the Voltage coming up. It´s 4.8V with full load.

>...the wiring that powers ignition and runs to coils...
The white ones. Have 12.4V with ignition on at the coils and 10.4 during cranking up. Looks okay for me. Could check again at the amplifiers for 12V. Had just prooved for continuity the the Amps.

Either I oversee a simple thing or it is a little strange...
Still any ideas welcome!!!

Tom

 

More than once I have forgotten to connect the fueling ECU after working in the car and it ran horribly. If I had that, with other issues in combination, I doubt it would run at all. The vac tub on that balance pipe is important. Check it. Use your mouth to put a vacuum on it. Use a lip or tip of tongue to see if it's holding.

I'll say again. Peel back the tape and have a CLOSE look at the connection circled in red in the photo. You can see how central it is to spark and right ignition. If you peel back the tape and all looks good, tape it back up and keep moving forward - aka - keep it move'n - as we say here in the states.

Below are a few snaps of what mine looked like under wraps... After refreshing this wire set up the difference in the car was amazing. More,,, if I would have measured I probably would have measured 12v...or something that seemed "normal"... Just say'n

 

Thanks Jay, I will do that tonight!
Just pulled out spark 3A - just wanted to check, whether it´s still wet. Left the hole open. Upon cranking with 3A open it nealy started. Maybe the starter turns quicker, I don´t know.
Will check these things above... the vac and the 12V feed junction.
Thanks you so much,
Tom

 

Tested both vac line - they are on place and hold the vac.
Peeled of the white wire junction. It doesn´t look nicely, but it´s crimped and soldered. No loose wire or suspect signs of oxydes.
Outside summer and no ride...

 

Yeah - no fun! I feel your pain.
I just went and read back to you first post... Have a question.

When you say repair, what do you mean? NEW sensor? Or repaired, like splicing wires...?

This is a shielded wire, correct?
The CPSensor. Crank Position Sensor

 

> When you say repair, what do you mean? NEW sensor? Or repaired, like splicing wires...?
> This is a shielded wire, correct?

Hmmm. When I openend the isolation of the old loom I found a blue and a white wire going towards the fuel rail. This matches with your wiring plan above. White is the shield. I did not unpeel more of the dual wire loom, but I could not recognize the white wire as a shield. Both wires were just separate. As there was no plug and socket any more (someone had cut that before) I just resoldered the wires. As this was not solving my problem, I took a used CPS of my donor car. Here I had to solder a socket to the blue and white cable, as my donors CPS came with a plug. I used a socket from an injector as these fit. Unfortunately I did not mount that donor CPS at the crankwheel - I wrote that above. But later I realized and corrected that. Thus I have a tachometer signal when cranking now.
But you are right, I just spliced. No shield provided.

 

Hi Coindigger

The White Shielding Wire goes from the Engine Bay to Pin 24 of the ECU and is Grounded at the ECU end only, which is inside the Fender Wing of the Boot/Trunk and this is used to send a Signal to Fire the Injectors

So it isn't for nothing that it is known as 'The Dreaded White Shielding Wire'

If you are in any doubt about its integrity, You can get a long length of Coax TV Aerial Wire and run it from the Engine Bay around the Outside of the Car to the ECU in the Boot/Trunk to Test it

Remembering it is only earthed at the ECU end

Hope this helps

Alex

 

Thanks Alex,
I see, I have to be more precise what I am doing.
Two weeks ago I tested all the injectors. I bought those chemical beakers and cranked a while. All injectors were running fine and there was no difference in volume.



testing the injectors


12 injectors giving perfectly same volume after some seconds of cranking

Then I inspected the 12V junction. This was the point jay recommended


the 12V junction providing power to 2 amplifiers and 2 coils


12V junction - here resoldered and additionally provided with 12V from battery



spark system loom ground - here additionally grounded - just to proove that´s not the problem


both coils with new plugs - plugs were old and cable worn



new shielded CPS connector

old CPS wiring - this white wire I meant, Alex - it is a shield for the blue one to protect the CPS signal



I made a new CPS plug here and used shielded wire - just to prove that a small way of unshielded is not the reason for my problem


the shielded ECU-EFI connection pulsing the EFI from the ECU from the CPS signal
That is the white wire you meant, Alex. But as my injectors are firing nicely I do not exspect a problem here...


perfect ground


So far.
No Success.

A mean I either oversee a very basic thing or I do have a severe problem - I am frustrated...

I have a lot of Xylene in my tank to clean the injectors, but I never read that this should be a problem.

Any help - still - very welcome.

Tom

 

still thinking...
what I could do additionally?
I am quite sure it is not rotor, plug lead set, distributor. I checked timing as well. On TDC the rotor shows straight downwards.
All three 120 degree mounted pieces on the crank whell are still there to trigger CPS and one is just perfekt on TDC of A1.
Anyway I still want to try to oberserve the timing signals with the oscilloscope.

Is there any possibility that the camshafts are out of sync? But this would not come just by standing in the garage.
Is there any chance, that the valves are not opening enough? To let fuel and air in? But on all cylinders. Unlikely.
Is there a chance, that ECU or/and EFI get a false timing? But why?
I still consider my fuel gone bad. But this is weird isn´t it?

The last thing I remember I did, before it lacked starting, was to remove the auxiliary air pump connection/valve.
I left the central hose to the 12 cylinders open, I closed it and a blew 1bar of air into this... but no difference at all.
Might I habe blown debris somewhere in there, that prevents the start of the engine?

Still searching solutions...
Tom

 

Hi Tom

Just thinking out loud, might be a good idea to drain the Fuel Tank

If you look underneath the Car, underneath the Sump/Tank is a Rubber Grommet and if you remove that Rubber Grommet, you will see a Tap to drain the Fuel Tank with a Spout on it to put on a Tube to drain the Fuel into a Can for disposal, or use in the Lawn Mower

The only slight problem being that you may probably find that the drain Tap does not line up with the hole, so you may have to loosen the Bolts on the Sump/Tank to move it over a bit

Also Lower Coil 'Red' goes to 'A' Bank and Upper Coil ''Yellow' to 'B' Bank and if you get those Coils mixed up as I did then She won't Start, 'Ask me how I know or rather Don't' and while you are about it Check that the Two Main HT Leads that go in the Top of the Dizzy are in the right holes, which is another easy mistake to make

Have you taken an actual Spark Plug out, just to see if even one of them is Sparking?

 

Hi Alex,
I did repair the fuel sender, emptied the tank and cleaned the sump tank woth phoshoric acid as it was very rusty. I´m quite sure tank und sump tank are clean, just the Xylene I care about a bit... Installed new fuel pump and new filter, even in the sump tank. I did this, during I was waiting for the new rotor, plug lead set and distrubutor, when the car was already not starting...
I have plain 2.5 bar of fuel between both regulators and the injectors are workig fine.
I do know about mixing up the coils of A und B... do not ask eiher... but this is plugged correctly. I even tried to swap, but the effect is, that upon cranking in the event of firing you hear a immediate-stop-noise. so I made it right after this test. Thus I´m sure A-amplifier goes to A-coil goes to A-hole on distributor.
Sorry...