Hi,

after 1 year I tried to start it; just cranks, fuel ok, but no spark and no injectors pulse.

I bought a new crankcase sensor (front of the engine), replace it but nothing

could you please help with any ideas
engine V12 6.0 from 1994

thank you

 

There is also another at the rear, and that has been known to give grief.

Warren is the Marelli, 6ltr, Guru, and he will appear soon.

OB, Orangeblossom, has done heaps to his, and when to rain stops in the UK, he will slide in also.

My experience with them is almost zero.

 

Hi sososs

First off, I don't have any experience with a 1995 6.0L XJS

But I do have a 1995 4.0L XJS that had exactly the same problem as yourself and I also fitted a New Crank Position Sensor which Spectacularly failed to solve my 'No Start Problem'

Where never having worked on that kind of Engine before, I don't mind admitting that I was totally lost, so following the suggestions I was given on this Forum, I was only too willing to try every trick in the book

Except no matter what I tried nothing would get her to Start, until I had a suggestion from a guy called 'Paddy' who was told about this on 'another forum' where having tried everything else I would say that this was the last throw of the dice

Where I am pleased to say that it Worked! and was such a simple 'Fix' that my XJS Starts on the button

So while I don't know how your Car Compares to the way that my Car is wired up, as my knowledge of Auto Electrics is about Zero!

Its got to be worth a 'Shot in the Dark' to see if this 'Fix' works and gets your Car Started

Underneath the Passenger Side 'Knee Pad' of a (UK) Car is a Panel that undoes with a Coin and behind this is a multitude of Fuses, although instead of touching those, if you look just above them there are Two Blue Relays

Which may not even be there on your Car, as my Car is a 4.0L and your Car is a 6.0L

But in the event those Blue Relays are there, these is a possibility that the Blades on those Blue Relays can sometimes be a loose fit, so as I didn't have any other type, I removed and then reinserted those Relays and even swapped one for the other

Where after having done so, I just turned the Key and then She Started!

And this was after Weeks of trying just about everything else and so its gotta be worth a Shot

You can read all about the Tricks I tried including the very last one, that got my Car Started, on Page: 96 of my 'Cherry Blossom' restoration thread and here is the Link

How I got my XJS 4.0L Engine Started but only after trying every trick in the book

 

The first thing I would check are the front and rear crank sensors. These are primary inputs to the Marelli ECU without them there will be no spark and no tach signal from the Marelli to the Lucas.

 

front and rear crank sensors are identically ? or different
also can be tested by a multimeter ?

thanks

 

Hi SOSOSS

The Front and Rear Sensors are basically the same, except that the one on the Front has the Wire hanging down, while the one at the Rear has the Wire coming out an an Angle so that the wire is pointing in the right direction without being stressed

The only other main difference being the Price, as the Front one can cost Twice as much as the Rear one and 'No I don't know why either'

Just as a matter of interest or not as the case may be, I had almost exactly the same 'No Start' problem on my Car 'Cherry Blossom' which had been standing out in the open for something like 14 years!

No Spark and also No Injector Pulse!

Where 'Greg' and 'Grant' came riding to the Rescue and eventually we managed to get her to Start!

You can read all about it and everything we did to get her going on Page:11 of my 'Cherry Blossom' restoration thread, which should hopefully help to get your Car running

'No Start' XJS V12 No Spark and No Injector Pulse - 'How we got Her Running'

 

Quick question guys on the V-12 if you don't mind me piggy backing your thread. Will the '95, '96 V-12's have the rear crank sensor also?

 

They do, but the XJS and X300 systems are different. Both V12's have 2 sensors, but they are in different places. The XJS uses the two sensors ( one is crankshaft position, the other is engine speed) and they go into the ignition ECU. The X300 has a single ECU that does both fuel and spark and also adds a camshaft position sensor to the crankshaft position and engine speed sensors.

The V12 XJS kept a distributor to the end, the X300 used coilpacks, so the control strategy is different.

 

I have cleaned all the contacts that I could find, checked the resistance of front and back crank sensors (have resistance on the multimeter), but nothing - still no injector pulse and no spark ...

 

Hi sososs

Have you Checked for 12volts on the Electric Plugs that Clip onto the Injectors?

Did you Clean the Plug and Socket of the Silver Box module down by the front Headlight nacelle (That in itself might get the Injectors Pulsing) and fix your 'No Start' Problem

 

yes, I have sprayed and clean the silver module, CPU also the 2 black starting modules amplifiers

I have checked with multimeter the injector plugs and also by 12V light

 

Hi sososs

In that case it could be the Shielding Wire (aka 'The Dreaded White Shielding Wire') that commonly causes problems with Injector Pulsing but rather than shamelessly copy the advice on this from 'Grant'

Have a look at 'Grant's Reply' to Pounds Auto, who seems to have a very similar problem to yourself and 'Grant' can also show you how to Test the Continuity with your Meter

See: Grant's advice to Pounds Auto

 

On my Marelli ECU is a vac tube that when I found the car, had been sitting a loooooong while, I needed to check and RECONNECT that vac tube. Nothing happened when I turned it over and I'm not sure who it was that alerted me to it. I THINK without it, the ECU will not operate...

 

Here is the Marelli supplement it has info that will help you diagnose the problem.

The 3 primary inputs are the front and rear crank sensor and MAP sensor, if any of these are not functional the engine will not start.

What OB said about the white wire is also a good point, there is a connector in the V, mine was on the LH side under the injector rail. It is a large black plug with 1 wire white on one side, Check this is not corroded.

 

thanks for the info

I have checked front and rear crank sensor; but where is the MAP sensor ?

 

The MAP senor is inside the ECU in the passenger foot well. I would not think the MAP sensor would be bad, I would more suspect the hose from the manifold to the ECU. The MAP sensor hose comes from the rear of the A bank, my car has a very thin RED plastic hose. Pull it off and suck a vacuum see if it holds.

 

MAP holds vacuum - I tried with my mouth
but I have not felt any vacuum at manifold - kept my finger there while engine crank - probably not enough vacuum as the engine just cranked couple of seconds; all the vacuum exits at the manifold are ok

I will clean again all the contacts and ground wires

 

Hi sososs

Couple of things you could try

(1) Are the 2 Coils on the Engine connected correctly?

The Lower Coil the RED one goes to 'A' Bank

The Upper Coil the YELLOW one goes to 'B' Bank

If these are the wrong way round then She won't Start

(2) Are you able to trace the White Shielding Wire from where it starts to where it finishes?

Its only a piece of Coax, the same as a TV Aerial and so in order to see if that's the problem, you could get a length of TV Aerial Coax and run it round the outside of the Car

Connecting it up to the same places as the Original White Shielding Wire, as this White Shielding Wire is a well known cause of Non Pulsing Injectors

Hopefully Warrjon will jump in and be able to tell you exactly where those connections Start and End between points 'A' and 'B' if you can't see them

 

the engine and transmission were fitted on an off road extreme buggy 2 years ago - at that time started with no problems

since then I have put the buggy under a cover - and now intended to start it again - so since then no one has changed anything at the engine

 

Ok lets go back to the start.

1 - Turn the ignition on and the injectors should click, this is the priming pulse and is independent of the ignition ECU, ie it does not need the tach signal from the white wire. If there is no priming pulse then you have a problem with the injector circuit. This could be a number of things.
a - Bad connection at the power resistor or ECU
b - wiring fault not uncommon in the V
c - Bad ECU

Go through this and report back. If this does not fix it well try some other things.