starting/charging questions

[ak46champ]

Hello, I have a question on starting and charging for my 6.5td. The gauge reads 12v even when the truck is running. I checked the batteries and the right one reads 13v running and 12v not running. The left battery reads 12v running or not. I checked the alternator and it reads 14v. The starter clicks on some attemps and then starts. And others it has a slow crank but starts. And other times it starts ok. Temp outside is 70 degrees. So my question is why do I have a hard start at times and why doesn't the charging system indicate a charge with 14v comming out of the alternator? I just installed JK performance ECM.

Thanks?

[rapidoxidationman]

If both batteries are connected you should get identical voltage readings with the same meter at each battery. If you're not then you likely have a corroded terminal and judging by what you've written I'd say it is the (+) terminal on the passenger side battery that has issues; it has the lead to the starter. On my truck it loosens up regularly and requires a thorough cleaning of all the battery terminals at least once a year. It's also worth making sure all the grounds are in good shape on the truck. You might even check the hot lead into the starter solenoid; tough to get to but it can loosen up as well. Good luck!
Rapid

[ak46champ]

thanks I'll take a look. When I put in the new ECM I disconnected both positive connections. They are tight though. I will recheck.

[moondoggie]

Good Day!

In my experience, you should see ~ 14.5V at BOTH batteries with the engine idling. As above, if you see a difference in voltage between batteries, you've got connections problem(s) - R & R all of them. The dual positive connection at the passenger-side battery causes most problems, as stated above.

Every GM I've ever owned and/or driven (company cars) would provide > 14V at the battery at idle with minimal electrical loads, & a little less with the heater blower & rear window defroster on; this would go to ~ 14.5V on increasing rpm above idle (maybe 1000 rpm).

This could DEFINITELY explain your erratic starting behavior.

Blessings!