I'm completely in the dark when it comes to automotive wiring/electrics, so bear with me if I'm leaving important information out here. I'll fill in what I can!
Backstory - truck won't start if left over the weekend, sometimes even overnight. Temperature hasn't affected the situation. Alternator checks out good, batteries (for the 15th time) check good. Strangely enough, the last time the truck wouldn't start (would just barely crank, but not even close to starting) the batteries were at 92 and 95% according to the fine folks at O'reilly, but prior to that the batteries would always be low when I had them charged and tested. Starter checks out for function and electronics, no clue how much torque it's still putting out. Original starter as far as I can tell. Alternator is a reman installed a few months ago. GP relay is new late last year, I still have the old one and can swap out if the truck still won't start, to see if that changes anything. GPs are almost 2 years old.

Batteries pull 12.55 and 12.52 volts today, they came off the charger at the parts house a few days ago. They've sat in the truck for the last few days completely disconnected.

Multimeter readings on the 10 amp setting between neg battery terminal and disconnected neg cable are .20. The reader won't kick out a reading on the 200mA setting at all. Under hood light not activated. Does this fall within spec for our trucks? If not, what's next?

 

Check your grounds and cables... corrosion is their enemy.

 

.2A is too high (the workshop manual lists a maximum of .05A), although I don't think it should kill two fully charged batteries overnight.

I would start by pulling fuses until you find out where the .2A draw is coming from. After that is corrected, see if the batteries hold up longer.

I'm not sure why your meter doesn't show a reading on the 200 ma scale. Could be that it's just over 200 ma (does the meter display OL or flash?) or perhaps a protection fuse in the meter is blown.

How is the starter's cranking speed once the truck has been running and the batteries are charged up?

EDIT: ^^ And do like Christof13T says, check the battery positive and ground cables (both ends).

 

With fully charged batteries, start pulling fuses one at a time looking for the one that changes that .2a reading to a lower one. Be aware that open doors turn on dome lights. Radios have a slight draw for memory. Computer systems sometimes have a slight draw all the time too.

 

Try this utube video. It sure helped understand how to do the test.

 

First of all... fantastic video garydmundy. That's a great find.

200 mA ain't it. 200 mA for 48 hours equals 9.6 Ah used... you have 130 Ah available with the alleged good batteries that the Irish vouch for. My wording may divulge my level of confidence in a clerk that was hired off the street. The kids at McDonalds don't cook... they open, heat, and sprinkle. The clerk at the auto parts store clips and pushes a button.

Rant aside, let us delve into this a little deeper. I've attended this rodeo before and we were hamstrung by the meter being on the wrong setting, attached incorrectly, and misinterpreted by the operator. This is with all due respect to the operator... there are very few electronic technicians out there.



Most multimeters are good for up to 10 amps, so have a fuse (or 5) for your meter on hand if the draw exceeds 10 amps.

1. Solid connection with truck on the black cable, and wherever your red cable goes
2. Batteries clean, no coductive gunk on surface
3. Multimeter set to Amps
4. Unplug everything from the cigarette lighter sockets
5. Make sure anything with a light switch is off... including the overhead
6. Like the video says, don't open any doors when connected to your meter

For the sake of those with old-school multimeters (must get polarity correct):

If the red cables are lifted:
Touch the black meter lead to the red cable
Touch the red meter lead to the positive battery post


If the black cables are lifted:
Touch the black meter lead to the negative battery post
Touch the the red meter lead to a good truck ground.

I triple-checked my wording to make sure I didn't mix anything up.

 

Seems like before he pulled all those fuses, he would have seen the light on.

 

He could have used the light to make a training video... or the horn. I think he chose wisely.

 

This guy is fantastic. I ran across his channel on Thursday.

I haven't been able to find any corrosion on the cables, the terminals are corrosion-free and clean (other than the red anti-corrosion gel I have on there at the moment).

I'm not sure why the 200mA setting wouldn't kick a reading, it stays at 0. It does have a protective fuse on that setting, not on the 10A setting (not an expensive enough meter probably, but I got what I got). It recommends not keeping the meter on 10A connected in the circuit for more than 15 seconds or so.

Starter speed has never been stellar, even when warm, but the speed was less worrisome than the dummy battery meter in the cab, which hangs around 9 volts when the truck won't start, so it's obvious when I turn the key if she's going to run or not that day.

Rich, I get your rant. I have some of the same qualms, but don't have any equipment of my own to speak otherwise. I asked if they could check the torque the starter was putting out, but no dice. Just like I continually ask if the batteries go on what I call a real-world load test, pulling the same voltage that the GP's pull during their cycle. They have no clue, neither do I. I could always go to the dealership (if I feel like handing over my wallet) but I vowed to never set foot or tire on their property again.

I'll start with fuses, maybe borrow a better multimeter. As far as the "big ticket" stuff goes, the starter, alt and batteries, hopefully things are in order.

 

Left this out - I followed the steps in checking draw explicitly when I checked earlier today. I'm confident in the reading I was getting, the first time I had the hood fully open with the circuit to the hood light on - now I have a little dip in top of the neg battery post shaped like the tip of the multimeter probe. Made double sure that light wasn't activated with the next four readings.

 

That's what's known in technician's parlance as a "smoke test".

Your best shot at a good test is to charge up your batteries, then read the volts on them with key on (no starting). If you dip below 11 before you even crank (glowplugs on), you're batteries are done. My batteries were at 11.7 after a week of leaving a whole bunch of electronics idling in the truck... and they are normally at 12.0 before I crank (all readings glowplugs on). I'm getting ready to post "start stuff" in the AE class... it will show my battery voltage in there.

 

Well, it passed the smoke test with flying colors.

I'm going to check that again tomorrow, I think it was low 11 or high 10 today... can't remember. Again, that was on batteries that were 12.5V, off the Irish charger.

 

if you have a starter alternator rebuilder shop around they would be a lot more reliable to test your electrical components.

 

Well, a lot has happened since I started chasing this issue. Ran out of time before the baby was born and needed the truck, so I turned it over to Tom's Automotive Repair in Monterey. Great shop, excellent communication. Turns out previous owner had wired gauges incorrectly, they were drawing even with the key out - around 120mA pre-repair, now 19mA.

They also said the starter is getting worn out and the batteries are "good, but at the low end of good," and suggested warrantying them out with the boys at "O" to get a fresh set of better quality batteries. The good news is after the truck sat all afternoon yesterday and all night, it started up this morning without a complaint! First time in quite a while that has happened.

 

That is so obscure. It would have been near-impossible for us to troubleshoot on the forum. This is one of those drawbacks with modding: If done improperly and undocumented, you can be left out in the tall weeds when it comes time to service. I'm glad they found it and thank you for letting us know how that turned out.