I tried to start Redrover a couple days ago for the first time in ~6 weeks. Since I drive it infrequently, I keep it on a battery tender.

When I turned the key, not only did the starter not turn over and the solenoid not click, but voltage was low to all systems. The UltraGauge lit up, searching for data from the ECM and BCU, but it was not able to complete its initialization sequence. No dash lights when I turned the key to Position II.

When I checked the battery voltage with the multimeter it was 13.85 volts. I knew the terminal connections were clean and tight, but I removed them, cleaned them, and ensured they were tight when reconnected. No change.

In my 14 years on this and other DII forums, I don’t recall ever seeing these symptoms discussed.

Electrical system problems can be notoriously challenging to diagnose. I will nonetheless painstakingly take my multimeter and go to work this weekend using the Electrical Circuits and Electrical Library documentation.

My mantra is diagnose, diagnose, diagnose, and I often shake my head at some of the people on this forum who appear to have not tried to diagnose their truck’s problem. But here I go. On the off chance this problem is familiar to someone I invite your input. Thanks.

 

Check the other end of the ground strap where it connects to the body.

 

Do you mean the ground strap at the rear of the Bank 1 head? (I think that is the only ground that has a ground strap, and not a cable or wire.)

 

I would check to see if you're getting good power to the fuse box in the engine bay and work my way from there. That's where a lot of the modules gets powered from so I'd check grounds and leads there first.

 

You may be on to something, mollusc. Thank you.

I removed the ground strap from its firewall connection point and did a half-assed attempt to clean it. (It was getting late ...) After reattaching it the results were largely the same but there was evidence of a little more voltage (e.g. there was a solenoid clicking inside the cabin and the interior lights were visible, if dimly.

I was not looking forward to checking every one of the many earth points shown in the Electrical Library, but perhaps many (or all) of them in the body connect via the braided ground strap at the rear of the Bank 1 head. That would make sense.

I'll disconnect it again when I can, clean it more thoroughly, and report back. I just hope I don't need to disconnect it from the rear of the head. That is much more difficult to reach in situ.

 

Don't forget the ground that runs over to the Alternator bracket. It can be mounted high or low, but it's one of the big ones for sure. There is also that ground area just before the negative terminal itself which has a good amount of smaller grounds which go to the under fuse block.

 

I know it is along shot but even though the battery is good for voltage could it be bad and not providing the required amps.
I have trying to track low voltage to the cab myself it is .6 lower after a while than what is at the battery with the engine running - try a fuse tap to see what you are getting at the fuse box, I use an add a fuse and cheap led voltage meter. Ground off to a bolt on the fire wall, pop the fuse into the accessory circuit and see what you have

 

Thanks Richard. I can appreciate the amps being too low to power the starter, but it's difficult for me to believe the amps delivered would be so low as to not power even very low amp circuits. That said, the battery is 3+ years old (with a 36 month full-replacement warranty).

The first thing I did was to run out and buy a new battery. I did that before checking the voltage of the old battery. I can easily install it and see what happens. If it doesn't cure the problem I can return it, which I was going to do anyway.

 

@mln01 I know it is a long shot, but I had a battery that had a solid 12.6 but would not crank or even turn the lights on - I am not an expert on batteries it appeared to be an internal issue with the battery.

It also occured to me check for rodent damage, I have some experience with that.

 

Just this weekend I had that issue on my motorcycle. It had 12.6V but wouldn’t even power the instrument lights. I suspected a bad connection so I cleaned all the main pos and neg wires. Still nothing. So I tried jumper cables from my Disco. It kicked right off. A new battery solved it.