no spark to plugs- jaguar xjs late 1989 approx.

driven 3 hrs has a morelli ign. had good power and smooth running after rough starts.

drove into garage for spark plug change. removed upper coil and cruise control to gain access to plugs. changed plugs one at a time.

engine cranks great but wont fire.I have 12 volt's to both coils with ign. on.

What could I have done wrong????

 

What spark plug gap did you set for your plugs? Should be .025"
What spark plugs did you use? NGK are recommended.

Did you double-check the firing order? Even though you changed the plugs one at a time a visual double check is always good.
Also visually double-check the wiring on the coil you removed.

Next check that all the plug wires are seated firmly. The plug wires on this car are a real bear to get seated at times.
This goes for the wires at the distributor too. Especially the two coming from the coils.

I don't get the 'click' I would on other cars letting me know the wires are seated properly so do it visually looking at the depth of the distributor and plug ends.

 

Welcome to the forum jdholly,

Good to have you here with us at Jaguar forums.

Follow this link XJS - Jaguar Forums - Jaguar Enthusiasts Forum to the XJS forum for help, advice and information. The 'HOW TO' thread at the top is a good place to start for info on regular issues.

Please remember to add vehicle details to your Signature to help others to give relevant advice. Go to the User CP button on the left of the top menu bar, then Settings & Options under Your Control Panel. Select Edit Signature and enter the details.

You can also visit the US Western Region forum by following this link https://www.jaguarforums.com/forum/w...t-hi-wa-id-38/ to find other members in your region.

Enjoy the forums.

Graham

 

Welcome!

 

welcome

 

Welcome to Jaguar Forums jdholly,

Good to have you with us.
Enjoy the forum.

If you haven't done so already you should add your car details to your signature to help others to help you.
If you need help with getting around and using the forum follow this link for some help Forum Help

 

Hey there and welcome aboard again.

As you already have an intro thread, this one is moved to the XJS section for you

 

Welcome, JD!
This IS the place to be if you're a Jag owner, where knowledge and experience of the marque abound.

 

Firstly welcome this is the best Jaguar forum on the net.

A couple of things to check. There is a sensor on the LH water rail near the front if this is not connected correctly the car will not start

There is an inertia switch on the drivers door pillar make sure the button is down.

As your car is a Marelli the plug order on the distributor cap must be followed. It is not like a regular dissy that follows the firing order around the cap.

If all these are good. Then pull a spark plug out and ensure you have spark. If you have spark then listen for injectors firing.
Start with this and report back.

 

What should you be listening for......to make sure the injectors are firing off?

Thanks,

DaveS
89 XJS Collection Rouge

 

Take a long screwdriver if you don't have a mechanics stethoscope, and put it on each injector. Hold the handle next to your ear and listen for an obvious ticking sound. This is the injector working. I had this problem with my 82. 2 were bad. But! the car should still start even if two are bad it'll just run very rough. Bud

 

thanks for feed back, nothing helped,just found no fire to injectors either.

 

So you have spark but no injectors firing, is this correct?

If so you need to check the tach signal from the Marelli to the Lucas, if the Lucas is not seeing this signal it will not fire the injectors. I can't remember off the top of my head which pins, I will look it up when I get home from work this afternnon.

 

Any luck with getting the correct info on the pins to check the tach sensor.

I'm having the same problem, no fuel. I have spark and good fuel at the injectors.

Thanks,

Dave S
89 XJS, 38K miles

 

Sorry - completely forgot. Pin 24 on the Marelli goes to pin 18 on the Lucas. This is a shielded wire so check that the wire has continuity and that the shield has a good connection. I do not exactly where its grounded but I would expect at the Lucas end ONLY.

Another question - have you replaced the Lucas ECU? because the 16CU ECU for the Marelli engine is different than the 16CU for Lucas ignition.

 

Just to clarify my last post pin 24 on the Marelli ignition computer goes to pin 18 on the Lucas 16CU injection computer.

On my car the Marelli ICU is in the passenger (Left Hand side) footwell under the A pillar. I do not know if this was moved to the passenger (Right HAnd side) footwell in a LHD car.

 

thank you thank you no results yet.please help.89 xjs marelli ign.will not start .was running fine.turned off key and changed spark plugs.old plugs had nice color.has not fired since.cranks as always. I have checked wires connections ,and can not find where I might have screwed up.
with key on 2 wires are hot to each coil and 2 wires are hot to each injector.injectors are not fireing when cranking .plugs are not fireing when cranking.tach is not moving when cranking. fuel pump with key and cranking has good pressure and volume. sorry I know less about computers than jags.thanks for any help!!!!! warrjon I have also followed all of your info lately. thanks

 

Firstly you need to go over what you have done, the Marelli distributor cap has all of the cylinder numbers molded into the top, check that all of these go to the correct plug. Make sure you have the correct plug in the input and output of the coil, these should be labeled A and B banks.

Next as you have been on the valley moving things you need tho check for broken and/or shorted wiring. Look for wires with broken or damaged insulation.

If you are not very mechanically minded this might be very difficult to fault find remotely, you may need to enlist the services of a professional.