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I have an 86 305 full size. Ive never ever had a problem with this truch once...knock on wood. Anyway The other week I drove to work, ran inside and came back out to try and start my truck and it wouldnt kick. Sounded like the battery was drained. I got a jump from a buddy and I was ready to roll. Thru the past few weeks Ive realized that if I try to start my bronco up cold it starts no problem at all. But when I drive it, turn it off and try to start it again in like 5 minutes the battery seems dead and it wont start and I need a jump. Alternator tested and good...spark plugs and starter almost new. Wiring is clean...no rot rust loose connections. The batterys only a year old its just the fact that it starts fine cold thats throwin me off...any advice?
With the engine OFF use a multimeter to check voltage at the battery posts. Should be around 13V or so. Then Have someone put a load on the battery (2 power windows up at the same time should work) if your voltage at the battery drops to like 9V or something, you've got a battery with a bad cell.
If you need a new battery, I reccomend optimias. They cost more at like $125, but the have awesome capacity and they will outlast your truck.
Big boy, check your battery and grounds as previously stated, cold weather tends to make our batteries weak if(of any age)Ive had this happen recently thinking it was THE timing ,starter etc.With no load my battery checked 12.5 volts. Best part of it was i have a f-150 and swapped batteries and found the battery was weak . Good luck TR