91 metro cranking problem- Need Help!

I have a 91 metro 1 ltr. and after driving it, if you try to crank it up within 5 or 10 minutes after letting it sit it will not start. It will just turn but not crank. If you let it sit for about 15 to 20 minutes, it will crank just fine. What could be causing this?
Thanks.

I have a 91 metro 1 ltr. and after driving it, if you try to crank it up within 5 or 10 minutes after letting it sit it will not start. It will just turn but not crank. If you let it sit for about 15 to 20 minutes, it will crank just fine. What could be causing this?
Thanks.
What do you mean by "turn but not crank"? Is the starter motor turning but not engaging the flywheel? Or do you hear a click then nothing?

It trys to crank but does not run. It will not run for at least 15 to 20 minutes after you shut it off and sits.

sounds like ignition problem, next time it happens pull coil wire out of cap and place it about 1/4" from engine metal part and have someone crank it while you look for spark, if you have no spark its probably the distributor. if you do have spark its probably computer or fuel pump, when your trying to start it are you pumping gas pedal or holding it down?

I am just turning the key. It tried to happen today. It acted like it was going to fireup but sputtered alittle then it sputtered again and fired up. The engine is running alittle rich I think. There is alot of black around the bumper where the tailpipe comes out. I only get about 18 to 20 miles per gallon. How do you lean out the mixture? It acts like it wants to flood durning takeoff.