Hey Everyone,

So kind of continuing from my old post about a month ago where I am restoring a Series III.

Long story short, it was running but leaking from everywhere so rebuilt the engine. Connected it back together and it wouldn't start. After some diagnosis and a HUGE help from the members here, someone mentioned to check the grounds that come off near the rear of the engine. They were connected up to the starter motor. So we removed them, grounded them and started the car. It started but so did an electrical fire.

After cutting and putting all the wires back together again we are having trouble starting it. All 6 injectors are getting a live from the junction box near the front of the engine but only the 3 injectors towards the front are getting a live pulse which comes from the ECU. The 3 injectors closest to the bulkhead are getting a live from the junction box but not getting any live / to give a pulse.

I have opened up the ECU and everything looks fine.

Really struggling now and would appreciate any suggestions?

Thanks a lot in advance, Sam

 

The system works backwards to the way you think. All injectors get volts, but only fire when the ECU earths them momentarily, the earthing time obviously being proportional to the fuel supply indicated to the ECU by the various sensors. To protect the system from a short circuit there are resistances in a block somewhere in the engine compartment that are interposed between the injectors and the ECU.
Have a read of this: -
Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering
Roger Bywater was an engineer at Jaguar when the EFI for the XK engine was developed. Pag 6 has a fault diagnosis section