Originally Posted by
LSM
Can you tell if it is really running hot? It may be a temperature sensor issue indicating a false temp. If it thinks its too hot it probably won't let you crank it.
When you had the impeller replaced, did they give you the old one? Was it missing any blades? I've seen those break off and go inside the engine block and get hung up in the Exhaust Manifolds. That will limit water flow through the engine as it can't escape through the exhaust.
Take your board off the back and have someone drive as you watch the exhaust ports coming out the back. You should be able to see equal amounts of water coming out each pipe along with the exhaust. Its not going to be a full pipe of water or anything like that but you can see water coming out. That is how I new I had something plugged on my old Malibu. In my case it was getting so hot it was melting the exhaust hose coming off the manifolds, but I had zero water flow out of one pipe....