Have you had the car running recently or has it been sitting a long time?
If you pull that diaphragm and piston assy staight up and out and examine the tip of the metering needle (be careful not to bend it!) you should see some gas. If it's dry or there's some crud instead, you'll have to go deeper. Also examine the rubber diaphragm. If it's hard or there are any holes or tears, it needs replacement. Remember to reinstall that diaphragm back in the same position - it has a little 'tit' that locates the direction.

Happy Motoring, Mark

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DrDKW