How to fix cracked valve?

[waterbear]

Repairs on a valve should only be considered a temporary measure...the valve should be replaced, IMHO.

[Poconos]

Is gthe valve a generic Home Depot valve or something more expensive? Where is the crack and most important, what causes it to crack? Being on the suction side and the answers to the above questions, you may be able to fix it. But probably as Waterbear said, only temporarily.
Al

[pauster]

If you happen to have the smelly 2 component pvc glue, you could try to apply this sparingly over the crack. Even CA glue (loctite) might help - for a great selection of CA glues see www.leevalley.com - some are gap filling and have helped me in many repairs around the house.

But I agree, this should only be a temporary fix. A hose clamp (if it fits where the crack is) might relieve the mechanical stress on the crack - also temporarily.