Starting problems on Patrol 3L TD

Having problems with my GU starting in the cooler Sydney winter mornings.

I am finding I have to crank the car for 8 sec before it will start, sometimes this has to be done twice.

If I've been driving and switch off I can start it again straight away no problems.

I've checked the glow plugs and they all measure approx 1.2ohms each,
0.8 when all connected in parallel .......this dosen't add up if I use the resistance equations ....but I think this is not the problem.

Other things I can think of I need to check......

Coolant temp sensor being faulty ? (anyone happen to know the resistance specifications of this when its cold and hot?) ie Not allowing the glow plugs to pre heat enough before cranking. I've tried waiting 5 sec after the glow indicator goes off on the dash an it seems to make no difference to starting.

Fuel and Air Filter were changed about 20,000k ago?

Wife seems to think its harder to start when left parked facing UP a hill.... this makes me think I might have a slow air leak in the low pressure side of my fuel lines?

Anything else?

One strange thing that did happen two days ago was after getting it started after two 5 second cranks the engine light came on whilst driving to the garage to get a pink slip. When I picked it up the light had extinguished......have not seem it come on since?

Thanks

Paul