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How to check batteries (dual battery setup)
Hey guys having a little bit of an issue I need some help with. So the truck sat for a couple of weeks while I was doing a bunch of maintenance to it. Got it working again just fine. Thing is now on cold starts it is running rough missing a bit till it warms up a bit. I think it is FICM or battery related though.
The batteries test out at 12.7 when fully charged. When they read 12.7 the truck starts just fine and FICM voltage stays between 46 and 48.5 while cranking or running.
When I let it sit overnight or for a day the voltage reads around 12.4 12.3 somewhere in there. When I start it then the ficm voltage will drop to around 40v and it does a lope like idle unless I give it fuel and get rpms up to about a 1000 then it runs fine. After a couple minutes ficm voltage returns to the rocksolid 47 or so.
I know it could be the ficm but was also thinking it could be because of a draw on the batteries while they are sitting. I dont know how to check for a draw on a dual battery setup. Do you disconnect one completely then do a single battery like you normally would?
Thanks for any help.
2003 F350 Lariat 6.0L
MTW stage 1, 4" MBRP, IPR coolant filter, 05 front cover and water pump, everything else pretty much stock.