Hard start after S10 is warm

My 1985 Chevy S10 2.6 engine cranks fast on a cold start, but after the engine is hot it cranks slow as if the battery was bad. The rebuilt engine is only 5 years old and the battery is about 2 years old.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.