Glad I found this forum, very informative threads/people.
A little background: I purchased my first D1 (NAS96) 6 months ago. It was one hell of pieced together mess and I should have moved on.
Ended up buying it as it was a manual and it had no overt big ticket problems. The truck came without a fob, only a key.
Ran and drove fine, only throwing p0306 that I couldn't hear/feel.

Decided to do the HG for the usual reasons and everything went well considering It was my first HG job.
All together again and I went to throw the battery on the charger. It started to hiss and bubble at 10amp
and sure enough, it was 6 years old.

New battery on the truck and ready for first crank and here is where the problems start.
First noticed the driver's door locked had no input on the CDL whatsoever.
Try to prime fuel rail a bit but i can't really hear the fuel pump when it works.
Cranks but doesn't fire. get out, check for spark, none. Upon reentry alarm goes off.
Pull battery terminals and try again. I do this about 3 times. Alarm led is sporadic at best.
Eventually able to reenter and insert key without alarm sounding but now no crank whatsoever.

Did all the key tricks: EKA, lock unlock 5 times, key in position 2 when reconnecting battery, etc.
No change. My thinking led me to believe it was fault with the 10AS system or ECU as the CPS worked fine before
the head gasket job.

I ended up trying Rover96's bypass of jumping orange/black wires coming off the green connector on the 10AS.
That got me fuel pressure/cranking but still no spark. (I didn't check fuel pressure before jumping the wires, wish I did)

Where would you go from here? I don't want to start spending $$$ on sensors or ECUs.
How would I rule out the CPS? Is that the only thing that can kill spark besides ECU/immobilizer?
I think I'll check if injectors are squirting next.
All important fuses are good, I skipped over a few the nonessential ones like lighting.
Hood switch is missing.

All said I'd appreciate some direction. The disco is currently parked at a restoration shop.
I only have an Ultragauge for reading codes but the guys at the shop can scan it with their professional
scanners. Can most serious scanners reset/disable the immobilizer? Or can they tell me more than the UG?
Thanks

 

fought with my D1 and finally ended up swapping out both the alarm ECU and the main ECU to get it to work.then sent the not working ones to logan_gibson and he was able to shut off the alarm in the main ECU, but the Alarm ECU was toast. Been to chilly outside to reinstall them (today it is -17 degrees) but the plan is to get them back in the truck.

 

Thank for the reply. I might have to contact him or bring it to a dealer/specialist.
Had one of the mechanics scan it with a proper scan tool today and he couldn't find any codes.
I confirmed no injector pulse today as well.

Over on the LRO forum someone mentioned removing certain fuses.
Anyone ever try that? I'll report back if it works or not.

Kind of annoying, I had always wanted a D1 over a D2 because my impression
was that the first gen trucks were much simpler electrically speaking... and of course Camel Trophy!

 

No, most of the shop grade scanners cannot communicate with the 10AS and ECU to disable the IMMO.

Check the CPS connections, make sure you are getting a signal from there (shop scanner should see that).
Next, check the connection to the coil packs, make sure you are getting voltage there.

Next I would investigate the ECU/10AS, check with a local rover shop and see if they can read them and see if they working correctly. The ecu can have water ingress that will cause a No-spark or random spark issue.

Fuel pump relay sounds fine if you're getting power to the pump and full pressure at the rail.

To me, it sounds like you tripped the alarm and it has not disabled itself. The wire you cut should only effect sending a signal to the starter to fire that solenoid.
Red light on the dash is the obvious sign of this, but sometimes that is burnt or cut.

 

Thanks for the insight guys. A Bosch scanner was unable to detect any alarm codes but confirmed signal from CrPS.
Taking it in to a reputable specialist next Friday. They said they use autologic to run diagnostics.

Anything else I should have a professional check that would be out of the wheel house of an amateur mechanic?

Passenger swivel ball seal is leaking, maybe I'll have them repair that as well.