RD28 hard to start after Balancer replacement

Hey Guys.
My 99tdi 2.8 GU needed a harmonic balancer replacement. All went well, old balancer out and a new aftermarket one in. It was about half the price of a genuine, but has all the same bits. Fitted and new belts to the accessories and cranked her over for the first time. Took a little bit but she ran.
Since then she wouldn't start unless I cranked her for ages, even double glowing etc didn't make a difference (haven't hot wired the plugs yet, but am detecting between 10.59 and 11.76v beside each plug so recon they might be ok).
All the filters were replaced at last service and she started like a dream before the change. Once running she runs the full rev range without misfiring or chugging at all so I'm thinking maybe it's not a crank angle sensor. Can drive all day without a drama, just don't restart it (that could be the answer, if I could afford the fuel:smileyvault-cute-bi:smileyvault-cute-bi:smileyvault-cute-bi:smileyvault-cute-bi)
Any tips or suggestions would be much appreciated peeps.
Kind regards, Mark.
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1999 Build 2000 plated 2.8 Green ST Wagon

I haven't had the timing belt off it and the only part that was replaced was the balancer. This is doing my head in.....suggestions?

Before you start it, is the fuel primer on top of the fuel filter hard or soft when you try and pump it?

And when you say you double glow it... Try using the airbag light as your glow plug timer. Crank when it goes out.

make sure the crank angle sensor is plugged in correctly, also apparently if the sensor has any dirt on it they can play up. if its damaged the computer doesn't know when the engine is at tdc etc.

Thanks Ian and P4trol. I've tried the double glow sequence. And using the airbag light as a timer, there wasn't a change at all. If it wasn't for the balancer change I'd have pulled the glow plugs out but they are all reading a charge and as is the glow plug rail when the keys turned over. I'll take the belts off and pull the crank angle sensor out and give it a clean before I put it back in.
I popped in the Nissan dealer and had them run the fault code reader during start, unfortunately it didn't register a fault or error during start despite not kicking over. They were more than willing to look into it for me, but at $160ph I recon I can spend some more time in it myself.
I'll keep posting developments.
Thanks for your feedback guys, it's great to know that people are willing to share. Kind regards
Mark