Truck Randomly loses all power and dies.

[Jared Jackson]

So, if you followed a recent thread of mine, you will know that I just chased down an issue where my truck was dying while applying the brake, in gear. I traced that down to a brake light switch.

The truck has been running like a champ for a few days, but now a new issue has popped up.

Unlike the previous issue, this problem is random. The truck has sat for a few days. I cranked it up this morning and let it warm up since it was cold outside. I hopped in the truck and took off down the street and it just dies on me. The gauges all drop to zero and the clock turns off. It is as if someone turned the key off. It comes to a stop and then the gauges come back on... and then go off again. I can hear relay's clicking as it gains power and then loses it. I get it cranked back up and drive it back to my house and pull in the driveway. I put it in park and it dies while it is idling. The gauges continue to come on and off, like I am turning the key on and off. The truck isn't moving and I am not moving while it is doing this.

I parked it, hopped in my car and took off to work because I was already late.

I haven't had the chance to look at anything yet, but I was just creating this thread to document my troubleshooting and findings.

I am going to start with checking all cables coming from the battery, alternator, etc... Any other suggestions that I should check? Anyone experienced something like this?

I am going to do some Googling in my downtime and see if I can find anything relevant as well.

 

[454cid]

Did you possibly disconnect the battery when working on it the other day, and forget to tighten it back up fully? It sounds like loose-battery/corroded-cable type symptoms like I was telling you about before, but going from 0 to severe in such a short time would be unusual.

I guess, I would check wires as you mentioned. Take a look at all your grounds under the hood, too. I'm not sure if we have a main ground hooked to the fuse box, I'd look that area over well, too.

 

[Jared Jackson]

Turns out, the positive cable was a LITTLE loose. But rotating it never flickered the hood light.

I took the cables off, inspected them and re-installed tight as hell.

I took the truck around and it didn’t die!

I am going to take it for a longer spin this evening, I just zoomed home for lunch.

However, I have always been worried about this cable set up. Being my first gmt400, I didn’t think this was factory, but I am not sure! The cables are doubled up!

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[Jared Jackson]

You have 3 wires coming from the positive post... 1 to the starter, 1 to the Alt and 1 to the distribution box, kind of looks like a shunt there...

The PDB wire is one of the connections, and the starter/alt is another.

 

[454cid]

I took the cables off, inspected them and re-installed tight as hell.

That's how you crack a battery. There is actually a torque spec for the battery bolts. The connectors sort of have teeth in them. Maybe they've flattened out, or the lead on the battery has gotten chewed up, allowing the connector to twist. Also do not grease them like you would a top post battery.

I didn’t think this was factory, but I am not sure! The cables are doubled up!

Yes, that's factory.

 

[454cid]

You have 3 wires coming from the positive post... 1 to the starter, 1 to the Alt and 1 to the distribution box, kind of looks like a shunt there...

I don't know what you mean by "looks like a shunt".

The PDB wire is one of the connections, and the starter/alt is another.

What's a PDB?

Something I forgot about, because I eliminated it... there is a spacer in the positive cable assembly, made of lead. It can flatten and not allow the connector to be tight enough.

 

[Jared Jackson]

That's how you crack a battery. There is actually a torque spec for the battery bolts. The connectors sort of have teeth in them. Maybe they've flattened out, or the lead on the battery has gotten chewed up, allowing the connector to twist. Also do not grease them like you would a top post battery.



Yes, that's factory.

No grease, new battery, I used a tiny 8mm wrench... I didn't hook up my breaker bar to a cheater pipe and hang on it, lol. When I said tight as ****, I just meant the terminals aren't moving. The teeth looked good.

 

[Jared Jackson]

I don't know what you mean by "looks like a shunt".



What's a PDB?

Something I forgot about, because I eliminated it... there is a spacer in the positive cable assembly, made of lead. It can flatten and not allow the connector to be tight enough.

Yah, the spacer looks pretty crappy. It's not flattened out, but it's chewed up pretty good on one side. How did you eliminate yours?

PDB - Power Distribution Box


Google: Shunt
It "LOOKS" like a shunt, but it isn't. I was just using something I knew to describe what I saw.

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[df2x4]

Seems like you already got it figured out, but I just wanted to second the notion that this sounds like a battery connection issue.

 

[Jared Jackson]

Seems like you already got it figured out, but I just wanted to second the notion that this sounds like a battery connection issue.

Yah, with my luck lately I was expecting a battle. Looks like it may be an easy fix. Might need to find a way to replace that spacer to secure the connection better. I need to also borrow 454cid's torque wrench so I can get these bolts to spec!