Hi all, greetings from Spain!

im a new owner of a xj12 1988 5.3 HE.. (is a daimler double six).. im trying to put him back in life.. as i bought it in not running conditions... the car was sometimes starting, and most of the time not..

Now im replacing all the inyectors, distributor, lucas 14AB amplifier, leads, spark plugs, coil, fuel pump, filters...

now im trying to starting and it doesnt... im checking if there are spark coming from the coil, and sometimes it comes, and sometimes not (with out modifying nothing, just putting the key, and cranck.. sometimes i can see a very soft spark with a spark directly connected to the coil, and sometimes not...

So i need some advise where to start looking at..

 

Sometimes the ignition switch fails.

Run a jumper wire from the battery "+" post to the coil "+" post and see if you get a healthy spark when cranking the engine. If so, suspect the ignition switch or wiring from the switch to the coil

Cheers
DD

 

Also check the setting of the TPS (throttle position sensor) under the capstan, and also the state of the two wires that plug into the AB14 unit and come up from the bottom of the distributor.

 

done.. .everything remaing same.. no spark from the coil.. (i tried with another coil as well, both brand new)

 

what is the TPS? where is located??

the two cables from the AB14 and the distributor itsetlf are brand new, conected... no im just trying the Coil.. there is no spark from the coil... so im not coneected yet the coil to the distributor...

 

The throttle position sensor is under the capstan (the thing that activates the throttle rods to each side). You have to remove the capstan to get at it. It is what tells the ECU how far open the throttles are.
It is tested by showing 0.32v at closed and a steady increase to 5v at wide open. It can be adjusted by loosening it and repositioning it slightly, but that is the setting to aim for.

 

The TPS can be adjusted after you solve the "no spark" issue

It's beginning to sound like the pick-up in the distributor is failing

Part number AEU1721



This is what "triggers" the coil, just like breaker points did decades ago

Unplug the pickup and measure the resistance between the two wires. Spec is 2.4 to 4.8 ohms....I think. I'll double check that spec when I have time.

Also remove the distributor cap and spark shield to inspect the pick-up visually and check the air gap to the reluctor wheel or "star wheel".

Cheers
DD

 

Ahh, ok.. my car has two... if im looking the car from the front, one is on the left side.. and another (i guess the one you are talking about) in the right...

 

thanks a lot for helping..

distributor is brand new as well...but i i will measure when going again to the car..

 

Have you tested for 12v at the coil positive lead? This is a solid white wire.

 

Two of what, please?

 

Agreed! Sorry for the diversion!

 

Yes, I do have 12v from this wire, then connected to the coil.. and I connecting this to the + in the coil.

​​​​​​IN the negative, I connect the two other cables coming from the Lucas amplifier...

 

As you can see in the photo,there are two... One in the red circle marked, the one you are talking, or not?

And the other, in the opposite side, you can see it brand new In the photo... Do you?

 

From the Lucas amplifier:
One cable goes to coil + This is the solid white wire
One goes to coil - This is white with a black trace
One to the ECU (this goes rearwards and connects into a shielded wire in the loom) and is a thin white wire.
and one to the tachometer. (a thin white wire with a spiral blue tracer)

Have you identified these and know which goes where?

 

The marking in the red circle is the kickdown part of the throttle cable. This has nothing to do with the spark ignition. Where and what is the second one you refer to?

 

My suggestion is to go to the XJS (X27) Tech Section, ONE DOWN from this section, and read the stickies at heh top.
Especially the one headed "No Start of a HE V12........".
I KNOW you have a S3, but it is basically the same as the XJS, just got 4 doors.

It goes through things in a very systematic way, and should solve your issue.

My BET, if there is one, is the Condensor inside the Ignition Amp (the black box on the B Bamk Inlet manifold) is shorting to earth. VERY common, throw that condensor away, it is not needed.

 

Strange.. as the amplifier is brand new, but I will try then the old one...

 

This done... Gives to me 3,16 K ohms.

 

Yes, I have identified all the wires... You can see them In this photo..