I have a 1993 XJR-S. (Original) Modified Lucas distributor with Zytek system. I've replaced plugs, wires, cap and rotor, had injectors cleaned and tested. Also replaced the wiring harness. I am getting power at the inertia switch and the engine turns over (new GR starter also). Of the two white wires going to the coil, one is 'hot' with the key in the run position. That's connected to the + end of the coil. The white/black wire is connected to thge '-' end of the coil. When I place the coil lead close to a ground and turn the engine, there's no spark. I've tried two different coils.

Should only one of the '+' wires be hot? Any suggestions what I could check next? Thanks. Larry

 

Welcome to the forum. Please go introduce yourself in the new member section. After 10 posts you will be able to use the features of the forum, which will let you search and find the answer to your question.

 

I'm not familiar with the Zytek system, but I'm sure others here are.
If this were an earlier system, I'd suspect either the pickup inside the distributor, beneath the rotor had gone bad, or the ignition amp was bad.

 

Also, WELCOME to our side.

Only ever seen one Zytec system, never touched it.

The wires at the +ve of the coil are "hot" with ign ON. The -ve are the one/s switched by the amp to supply spark, and tacho signal on some versions.

The -ve will fluctuate in volts as it switches the +ve side to earth, and that is normal.

I also reckon its an amp issue, as Jamey said, and bits for that system are near impossible to find from what I hear??.

 

Thank you for the suggestions. The system uses an AB14 electronic ignition amp so that should not be a problem to find. The rotor and cap are new so I feel OK with them although I will remove the cap to check everything is still intact. I ran a + wire from the battery directly to the coil without any effect. I have a spare coil and neither one worked. Could I ruined a coil by originally wiring it wrong (the + are - sign are pretty small for these tired old eyes). My next step is going to be to add a new ground between the engine and chassis. And test the coils (I used an old analog Sear auto analyzer to check them and only got 10 ohms for the secondary and 0 for the primary ... with a new 9v battery). I'll pick up a digital tester and try again. Larry

 

Larry,

OK mud is clearing a tad.

AB14 has a module inside, you new that, and I use Echlin modules, made in USA, and the part No is TP45, and I have had NO issues ever with them.

I doubt the coils are damaged by wiring errors.

It sounds like there is simply NO trigger for the -ve side of the coil to do what it should and supply spark.

FORGOT, hence the edit.

Inside that amp is a small capacitor tucked up in one corner, and held in place with a single screw, these capacitors short to earth. Unplug it from the module, remove the screw, throw it away, it is a noise suppressor??, and none of mine run them, and NO issues.

 

I read the piece in The Book about replacing the GM HEI unit inside the amp. I'll plan on doing that since $35 for that is a lot less than $300 for new amp(andI could also remove the capacitor if it's not needed. (I've removed 100 lb of sound deadening material ... what's a little bit more noise now?

 

Hahahahaha, a Jag owner with a sense of humour, LOVE IT.

There will be NO more noise, but that less weight will all count.

I have one coming tomorrow with spark issues, and I will first and formost remove that capacitor, and go on from there.

Mine was rusty looking, and I thought nothing of it, until I had replaced all I could think of to try and solve intermitant spark, and I reckon I simply forgot to plug in onto the 6th module at that time, and the problem had gone, and since then 7 cars have had issues with that little sucker. Think back to old points ignition systems and the "condensor" was the issue with too many of them, well this is basically a "condensor".

 

Just to cheer you up, if it turns out to be a Zytec ECU problem, there is a brand new one for sale on UK Ebay at about 900 UKP!!!!

Good luck with it, Grant is pretty sound on this stuff, I happen to know from personal help from him.

Greg

 

Update.

The capacitor in the one today was rusty as hell, VERY strange, since it sits atop a VERY hot inlet manifold????, BUT, his module was toast, someone replaced it without the paste and basically fried it. Capacitor removed, just because.

Took it for a spin, goes like stink, and starts on command EVERY TIME, and only stops only when turned off, how sweet.