So I'm having an issue with my 07 sierra. I just got the bottom end rebuilt and got it all back together, so I've had the wiring harness completely off and back on. Truck was doing fine, starts and runs, drives down the road. I didn't have my hood on for a bit, just basically making sure I'm not going to have to pull it again before putting it all back together. I've even been doing a little tuning trying to get rid of some burst knock I had and dial in the maf a hair.

Problem is randomly the truck won't start, sounding like either a low battery or bad starter. It just clicks one time real hard when you turn the key over. Sometimes when it is going to do it, when you first turn the key to the ON position, the power cycles on and off 3-10 times before it stays on and the radio comes on and all the lights on the dash come on as they should. Turn it on over to start it and it clicks real hard like the battery is low enough that it can't turn the starter over. When I say the power cycles, all the lights come on, then click off, then back on, all while the key is sitting in the ON position. You can really hear the fuse box in the engine bay clicking real hard as it's doing it. Doesn't sound healthy to put it mildly.

So it didn't do this for a bit after I got the engine back in. I had a battery that I knew was on the way out, so I just dealt with it a bit, charging the battery up and of course letting it sit for a bit while the battery charged before trying to start it again. This got me by for a bit, when the battery was fresh truck would start and run just fine, no power cycling or any other electrical issues outside of maybe the windows and such seeming weak when the motor wasn't running. It's an 07 so I didn't think much about it.

So it got to the point that it still would click and not start and cycle the power as I described even though the battery was full. Couldn't jump it, couldn't charge it enough with my trickle charger to get it sauced up enough to turn over. Just one hard click with the power cycling weirdly. So I bought a new battery thinking that would solve my problem.... No change whatsoever, truck would not start even though I even put the new battery on the charger for a night thinking it may have just bled off some while sitting on the shelf. So at this point it was consistently not starting over this after starting and running fine for a couple weeks after getting it put back together.

So I started looking over my wiring harness trying to find ground issues. The blatantly obvious one that I had tucked behind my fusebox when removing the hood and then motor was the hood ground, runs from the firewall to the hood right behind the fusebox on the driver's side. Was just hanging freely. I didnt have the hood on, so I just turned it around and bolted it to the same ground point as the ground strap that attaches to the back of the driver's side head. Didnt really expect that to do anything, but she fired up like nothing was wrong about 4 seconds after I got it bolted back on. I haven't read of anybody else having any BS like that happen over the hood ground not being there, hell some people don't even run them from what I've found on Google.

So I was thinking problem solved, truck was consistently starting, no issues. Have driven it a little trying to get it tuned, needed it for a couple trips into town, really haven't had any issues. Decided to reinstall the hood, and moved the hood ground to the point on the hood where it's supposed to be. No start. Move it back to the ground strap point in the firewall, starts right up. But, I've noticed that letting it sit for a bit, it seems to draw the battery down some. Last night I tried to start it after it sat for about a week and while the power didn't cycle like it was, it still clicked real hard like the battery was low or starter was bad.

So I'm charging it as we speak and I'm thinking it will probably start with a full battery, but I'm just at a loss as to wtf is causing this. I'm guessing another bad ground somewhere, maybe even one that I missed when hooking everything back up, but it's just super strange, especially with the power cycling like I have never seen. The charging system gauge and voltage readout in hptuners appear to be fine, 14v. I do think the battery is drawing down but not sure if a bad ground would do that.

Has anybody ever had an issue like this? What did it turn out to be? I don't have much experience dealing with electrical issues but I do have a digital voltmeter (that I don't know how to work.) I'm just basically looking for some input as to what you guys think may be my issue, and where I need to start. Was thinking of pulling out the battery and tracing the negative cable to the ground, as well as go ahead and take my starter off and make sure all those connections look good and secure. All the other grounds I know of appear to be solid. Any input is greatly appreciated!

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Attaching the hood ground strap to the engine, grounded the engine to the firewall. If that fixed the problem, then you have a broken or missing ground strap from the engine/transmission to the frame (or body), and possibly one broken/missing from the frame to the body.

Where does the negative battery cable go on yours?

 

Main ground from battery goes to front of passenger side head. There's another wire that branches off and appears to go under the radiator

 

OK, the engine is connected directly to the negative battery terminal, so it's grounded. There's a ground strap you mentioned from the driver's side head to somewhere on the frame? And you connected the one from the firewall (the body) to the point on the frame where the one from the engine was grounded? It sounds like there's a ground missing either between the negative battery and the body or between the body and the frame.

Basically, the negative battery cable, the engine (or transmission), the frame and the body all have to be connected by heavy ground straps. The one for the hood is obviously connected to the body at the firewall. When you connected that to the engine (through the other ground strap), things worked. That tells me that the body isn't properly grounded until you attached that (wrong, but it worked) ground strap to the frame/engine. I don't know your truck enough to know where the actual body to frame (or to negative battery, or to engine) ground strap is supposed to be, but that's what's loose or corroded through.