At 12.6 volts the battery should be fully charged. 6.1 volts is way too low during cranking. The most likely cause is bad connections at the battery cables. I'll bet you put the meter probes on the cable clamps. Put them right on the battery posts and measure the voltage again during cranking. If the voltage stays high there, clean those connections.
Monday, November 12th, 2012 AT 2:36 AM