That doesn't sound stupid at all, it just so happens that the truck does not have the proper dipstick tube, this may be an issue. I am surprised I'm not seeing an error code of sorts either on the truck display or in Pathfinder.

Ordered the correct tube, will let you know the outcome.

It might sound stupid but have you checked the engine oil level?

We now have a new flywheel sensor installed but the fault remains the same. At this stage I dont think the ignition switch is at fault. Looking more like a control board problem or wiring fault.

Thanks for the help Lindetech.

It should bring up a fault code when you unplug the flywheel sensor.
What is the tip of the sensor like? Any damage?
Should have 0.5 mm gap between the sensor and flywheel when fitted.
Sounds like an electrical fault that may be heat related.
I have had strange faults before and turns out to be the ignition switch.
Have you checked this when it shuts down?

Definitely no voltage to the ignition after shut down.

I had a look at the truck last night, it did the usual thing of shutting down within 20 mins then after unplugging the flywheel sensor, the LPG lock off and cooling fan, then plugging them all back in it fired up and ran for the rest of the night while I pressure washed it off.

Anyway, this morning its back to running and shutting down and not starting again. So last night was a red herring.
Thanks for the assistance Lindetech.

When I unplug the flywheel sensor while cranking it doesn't show any error codes, is this normal?

Are you getting 12vdc to the ignition pack aftershut down?

The LPG regulator is running at normal operating engine temperature. The spark disappears after shut down.

We have fit a new ignition coil as when it was inspected it was found to be corroded around one of the connections, but the fault still remains the same.

Are you still getting a spark after it shuts down?
Is the lpg regulator freezing up?