Starts fine then sometimes sounds like battery is dead

[Rusty Shackleford]

1988 R20 5.7L. Last fall the truck would start fine but sometimes would turn as if the battery was dying. It would start after a couple of tries. I figured starter and replaced that. Better, but eventually would start fine but on occasion do the slow drag start. In February, it wouldn't start and it sounded like the battery was almost dead. I was ready to call the autoclub for a boost but I tried it one more time and it started (with a slow drag turn) I drove to a battery shop and had the battery tested. I was told it wasn't great but not bad. I decided to get a new battery and it started fine for a while but normal start and the sometimes slow/dead battery-like start returned. I've cleaned the battery terminals and ground connections. Any suggestions as to what could be going on? Thanks in advance.

 

[gotyourgoat]

Sounds like weak output from the alternator. Of course loose connections in the charging system can mirror the issues. A multimeter or the place you went to test the battery should be able to give you a reading.

 

[82sbshortbed]

I'd check battery cables. Mine was doing the same thing. They looked OK but, I went ahead and put new ground cable and cleaned up the connection to the block and cleaned positive cable. It turns over fast now and never has cranked slow again.

 

[PrairieDrifter]

New cables, clean connections and battery posts. The battery cables and connections are most peoples problems. I just got some universal cables for the time being from a farm and fleet store, will be making my own custom length cables out of welding wire.

They're cheap too.