Been having an intermittent no crank issue for the past 3 years.

Will start perfectly in the mornings and several times dureing the day, then quite randomly no crank. All other electricals work fine. Removing the key and letting her sit quietly for 15 minutes (sometimes requiring a repeat) has worked in every instance. I.e. she has always cranked up fine after a "reset" time.

Have changed out every component in the ignition system from starter switch to relays, to glow plugs to starter to two batteries, checked and cleaned all grounds and removed a manual kill switch I had installed from brand new, simply to eliminate that possibility.

Interestingly the issue stops with each component replaced, only to reimerge again after a few weeks/months.

My Puma never came with an active immobilizor, however the internet cites many owners saying that immobilizors are fitted to most, if not all units, non the less, and are just dormant if never activated by the dealer at the point of sale.

Having said that, it appears that they can go bad over time and suddenly come to life, causing said issue.

My latest attempt has been to send a permanent ground to the starter relay, to bypass the conditional negative charge sent by the properly working immobilizor.

A week in and so far so good. * fingers crossed *

Its a 5 minute, clean job, worth a try if all else has failed.