Can't get my new drive belt on...'91 300CE

[rgnprof]

I have been in the middle of a water pump replacement on my '91 300CE (taking my time over the past several weeks)...

I have everything installed except the new belt - and I can't get it on. I have the right belt and I have it running correctly, just don't have enough length to get it over the last pulley (power steering pump). It doesn't seem like the tensioner is moving enough - to the left (?) I think...

Anyone got any advice? Thanks.

BTW, the tensioner is fairly new - within the last 2 1/2 years and 20K-25K miles...

ryan