Scenic II Not starting on cold mornings

Hi Guys, just wanted to borrow your expertise as my garage doesn't seem terribly knowledgeable.



I got the car last year. 2004 1.5 dci scenic. was a great starter but slowly started to get worse until now it takes 2 or 3 times to get it started.



The message on the dash at the end of the starting cycle is 'Check Injection'.



I took it to the garage and they couldn't find any problems on diagnostics. I dont know how much they tried as they just said 'well it started first time every time with us' Of course it did, the engine was already warm!



Anyway, I mentioned the fact it doesnt start on cold mornings and the check injection message and there response was to say it needed a complete rebuild as the diesel pump is probably gone. Quoted 'more than the car is worth'



I looked for other faults and stuck the multimeter across the glow plugs. 1 of them is reading a zero whilst the others are showing the same as the battery.



I plan to replace the plug (assuming i don't snap it off) to see if this will fix it.



Is there anything else i can check to make sure i am on the right track with this or are there any other avenues i should be exploring before i give up on it?



The engine was replaced by a different garage (who owned it as an mot lease car) just 27k miles ago so it seems a bit of a waste to get rid when this part is so new.



Thanks in advance for any help you are able to give.