Batteries read 12.7 but slow cranks

[Kakash70]

So I’m having an issue 1990 f350 7.3 na e40d truck after sitting for a couple hours it got a very slow crank like the batteries are dead but batteries are reading 12.6-12.7 batteries bought 7/23 both bought at the same time new regulator and alternator 6 months ago starter 4 months ago glow plug system 8 months ago I got a 0.06A draw but that’s not enough to kill the batteries within even a couple days charged the batteries outside of the truck 1 at a time after a day same issue.

 

[FrozenMerc]

Most likely due to bad connections, likely on the ground side. Check all cables and ends.

 

[u2slow]

For giggles ....
Measure the voltage-drop between the battery post and starter terminal while cranking.

 

[franklin2]

Yes, any voltage readings you take must be made while cranking. This usually requires a helper operating the keyswitch.

 

[u2slow]

BTW, 60mA background draw is on the edge of being a problem.

My FiL had problems with this. GPS, alarm, and satellite radio were stacking up to too much. Had to let one of them go in the name of battery life.

Edit: fulltime powered USB ports are another gotcha.

 

[ROCK HARVEY]

My bet is you need new positive and negative battery cables. Remember, if your voltage is dropping on the way to the starter due to bad connections or cables, the amps are going up due to Ohms law. You might even see the connection on the starter glowing red if it’s bad enough. Lots of starters have died this way.

 

[IDIBRONCO]

Have you load tested your batteries? Maybe they just can't produce the amperage needed to turn the engine over fast enough.

 

[IDIBRONCO]

Then again, it could be your starter.

 

[Tizzy]

I recently had a similar issue. Truck would crank fine cold. If ran for awhile, then shut off..then crank right after shutdown, would start fine. Let sit for 30 minutes to an hour…and would not crank like it had weak batteries. Thought it was injector pump going out. Turned out starter was weak and heat sink from engine getting up to temp then shutting off for awhile made starter too weak to crank engine. Put a Powermaster starter on, and problem was completely resolved. Starts amazingly fast now. Not saying it’s your solution, but could be a thought.

 

[Kakash70]

Well turned out when cranking voltage would drop to around 4-5. load tested both batteries and they have seen the end of their days. figured out the the amperage draw turns out to be the new sound system I put in couple months back. thank yall for the replies was just able to get time to get it all figured out.

 

[Greenie]

I tried various repairs trying to solve a slow start and finally bought a DB Electrical starter on Amazon (currently unavailable) in 2017 - the original starter was the problem all along; either the torque or the starter speed slowly changed for the worse over the years - not so much that I could notice it or think that the starter was the issue.

 

[KansasIDI]

I tried various repairs trying to solve a slow start and finally bought a DB Electrical starter on Amazon (currently unavailable) in 2017 - the original starter was the problem all along; either the torque or the starter speed slowly changed for the worse over the years - not so much that I could notice it or think that the starter was the issue.

Another viable option is a Powermaster 9050, if the DB starters aren’t available