97 4wd 2.7 Electrical Woes

About a month ago I noticed my truck was experiencing hard starting. Sounded like it was laboring and taking longer to start. Didnt really think anything of if until I went to start it the other day and it almost didnt start but did. After I arrived at my destination (luckily it was my house) I went to leave and the battery was dead. No big deal I thought my battery must've been slowly dying. So I pulled the battery out of my wifes car and put it in and she started right up (still a hard start). So I drove the truck the rest of that day and after 4 starts that battery was drained till it wouldnt even try to turn the motor over.

I thought my starter was bad, so I pulled it took it to 3 different places and it passed all test. Put it back on, charged my battery, cleaned the shit outta all terminals around the battery and made sure everything there was tight. So now I was thinking maybe the pos battery lead running from batt to starter was my problem. Voltage on battery post 12.9, voltage on terminal 12.9, voltage on starter 12.7. Then I hooked my volt meter to the terminals and tried to start it. When I push the key forward (not enough to engage the starter) it begins to slowly drop the voltage (almost like a stop watch counting down) then when I try to start it it significantly drops voltage until about after 3 sessions of cranking for a couple of seconds of weak cranking it drops the battery to where it wont even try. So now I'm thinking I have 2 bad batterys, so I have them tested (at two different places) and of course they both check out fine. I have made no electrical changes recently and are not running any electronics other than an aftermarket cd player. Any help would be appreciated.

Oh yeah and once its started Im getting 13.9v at the battery and it doesnt miss a beat.

 

Check all your ground leads as well. Replace anything that looks iffy.

 

I am sorry about your problem. To me, your description leads one to think about a big amperage draw. Your starter is one, but you have some relays and if one of them fails it will draw down fast in some cases. Pull out and look at your starter relay, your fuel pump relay, your primary (ie:Big Fuses) fuses and check them. Look at the blades or the terminals for signs of arc or burnt carbon look. Your Alternator could cause some problems if a diode assembly goes or the stator grounds to the alternator frame. If all of them are good and you still have your problem, you may some experimental problem deduction. Check this first, then we can do the obscure. Good Luck.

 

I had a similar issue when a relay for my KC Daylighters had a pole short out and kill my battery.

I agree with the above statements. Find what is causing the draw (relay or something starter related) then put a new battery in.

 

So after a i spent the whole weekend cleaning ground wires and fuses , testing wires and taking the alt to have it checked i had made no progress other than giving all that shit a thorough cleaning. I decided to pull the starter and take it to a guy who rebuilds them, and he found that the brushes needed replaced. What really pisses me off is that I had it tested 3 times the first time it was off the truck but apparently that test doesnt mean shit except that it will turn on, not that it is functioning properly. thanks for the help guys