Idler pulley question - help

I'm replacing my waterpump in my 04 2500 t1n.

I have the new one installed and I'm putting the new serpentine belt on when I noticed that the right hand pulley has a spacer behind the actual pully. The left one that attaches to the water pump (larger of the two) does not have one. Should there be one? If I install with out a spacer, it doesn't line up with the other pulleys.

Sadly the left idler pully hit the ground when disassembling it, but I don't find any spacers on the ground.

Thanks in advance.
Preston

The right one (when looking at the front of the engine) has a spacer behind it. The left one that bolts to the water pump does not have a spacer. I'm a little confused about you saying the left one was the larger one. Both of mine are same size and the parts manual indicates that the pulleys themselves are the same part number. I think the waterpumps are different between the OM612 engine and OM647 engine. Hopefully you got the right waterpump since they should all line up when the left is installed without spacer and the right is installed with spacer.

In case a picture will help....

Thanks Doug. I went ahead and installed both pulley and it started fine.
I reinstalled the ones that I took off and yes one seemed a little larger.
I did take pix. I'll upload once I get them into my Dropbox.

There are two different sizes (that I know of) for idler pulleys, as well as a smooth and a ribbed one. Don't have all of the facts but the basic takeaway - as I understand things - is that you can use the marginally larger or smaller idler pulleys with no difference in performance. The spacer obviously does matter as it positions the pulley in line with the rest of the pulley. See the note on Europarts-SD's belt kit below for a short explanation pf the sizes...

http://europarts-sd.com/item.asp?PID=2307