Hello, I bought a 2007 Hummer H3 2 months ago with 153,000 miles. Long story short, new battery haso been drained in 3 weeks time. At first, Hummer was completely dead. After charge, it was fine, until turned off again. It clicked at first the 2nd time, then died. Wouldn't start after several jump attempts. Assumed it was the starter. Mechanic came 2 days later to change the starter, but he jumped it and it started right up. He turned it on and off several times and it worked fine. He left without doing any work. Terminals were changed, problem continued. Battery will die after about 5 mins of being turned off. I read on here to switch the relay for the fuel injector with one from the defrost. I did that, and the Hummer made a clicking sound while still not starting and the check engine light was flashing, then it completely stopped clicking and wouldn't start. I don't know what the issue is. I need a mechanic to fix it, but when it starts perfectly when jumped. The battery is new. Also, I don't know if it could be related, but every time I put gas in it, it has a hard time starting. Like it wants to die, but it does start. Happens every time since the day I brought it home. Please help.

 

normal drain on batt is apx 115 ma. .115 amp. mine goes days and starts.
check drain with ammeter in series with one batt conn.

 

OK, you said the "terminals were changed".... to what?

Single most common electrical issues with H3s are usually caused by the OEM battery terminal connectors. Change those out to a quality aftermarket set (realizing that + & - terminals are different sizes) and you get rid of that issue.

Just because the battery is new, does not mean it is free from defects. Any man made part is capable of being dead out of the box. Intermittent internal shorting in a new battery is not unheard of.

If after fueling you are having problems, you have an EVAP issue, likely the EVAP solenoid valve. Common problem with your vintage and miles.

When you fuel do you keep going until the pump shuts off? If so and this is where you experience the problem.... next time put in just a few gallons, no more than 3/4 tank and see if the problem exists. If it is better after only partial fueling, that confirms the EVAP Solenoid valve need replacing. Cheap and easy DIY. Threads here on how to.

 

Wow, there is a lot of unknowns here...

1. Are the sun roof drains clogged and damaged the BCM
2. Are the battery terminals converted to quality one
3. Is the anti theft system engaged
4. When's the last time a tune up, maf, TB cleaning been done
5. Is the EVAP system in need of work
....etc.

There's just so many variables.

 

I would start with Doc Olds advise.
Always start with the cheapest fix first and see if you are throwing any diagnostic codes with a code reader (your local auto parts store will read them for free).