Embarrassed Myself Today, Then Made up for It

"Urambo Tauro" (urambotauro)
12/16/2016 at 18:00 • Filed to: wrenching, blog, discussion

So that !!!error: Indecipherable SUB-paragraph formatting!!! from earlier this year has been holding up pretty well. I don’t expect it to last forever, though. So I thought I’d swing by a local shop today for a quote on getting an all-new pan swapped in...

As mentioned in that earlier post, changing the oil pan in my Mustang is a big PITA. I do almost all of my own wrenching, but this is one of those tasks that I’m seriously considering letting a well-equipped shop handle.

So I stopped in to get a quote to help me make up my mind. Because the job involves lifting the engine and/or dropping the front K-member, this is a great opportunity to replace the engine mounts, so I asked them to make that part of the quote. Sure, it would inflate my price even more, but there’s really no better time to do it. At 174k, might as well just bite the bullet and do it all at once.

As I got back in my car with the quote (north of $600, BTW) in hand, the car decided to make a fool of me by refusing to start. Right in front of all these pros that wrench for a living. Great, now I look like one of those drivers that limps their car from place to place hoping that the problem fixes itself.

I’m just a weekend warrior home-gamer, but I take pride in my work. Yet here I am looking like a penny-pinching doofus in front of these guys. Just what DID I screw up? And when will I give in and just let REAL technicians work on it?

The car cranked and cranked, and sounded strong as it did so. Yet it would not give even the slightest cough of actual ignition. I popped the trunk, and sure enough, the inertia switch did NOT need resetting. So it had to be something else...

It reminded me of a time a few years ago when it had the same symptoms, and ended up being a slightly-bad battery. There’s something sensitive about these cars that they need the battery to be in tip-top shape to successfully start. Every last CCA counts. But THIS battery was relatively new, and still had a couple of years remaining on its warranty. the connections were clean and tight, and last I checked, there weren’t any excessive loads draining it overnight.

So I continued poking around, not seeing anything out-of-place. Was I going to have to leave it here and let them fix it? Soon, one of the techs walked outside, having heard my repeated attempts to start it. He glanced over the engine while I tried starting it again. Still nothing, not even a hiccup of combustion.

I asked if he had a battery cart or something handy. As I mentioned that these cars were kinda touchy about that sort of thing, I could see the doubt in his eyes. But the way I saw it, even if it wasn’t a problem with the battery, I had to at least rule it out as a possibility. He returned half a minute later with the jump-box and hooked it up.

Wouldn’t you know it, it started up within the first second of cranking. Boo-yah! I told you so! (Ok, I didn’t actually say that, but it crossed my mind...)

After thanking him for his assistance, I immediately drove over to the parts store where the battery came from and asked for a load-test. Bingo! It failed. It was producing only 537 CCAs of its rated 610. I borrowed some of their tools and quickly swapped a new replacement in at no cost.

Sweet! Gotta love !!!error: Indecipherable SUB-paragraph formatting!!! .

DISCUSSION (7)

Birddog > Urambo Tauro
12/16/2016 at 23:11

There is definitely something about 80s/early 90s Fords.

Urambo Tauro > Birddog
12/16/2016 at 23:27

I swear, the cranking sounded plenty strong. Just like it did last time I had to replace the battery. You really can’t tell just by listening to it. It didn’t sound like it was cranking any faster with the new battery. I wonder if there’s anybody out there with a trained ear that could actually tell the difference.

jimz > Urambo Tauro
12/22/2016 at 12:13

I think the PCM is supposed to be awake and operating down to either 9 or 9.6 volts. on an even slightly weak battery, the initial current surge to the starter can drop it below that causing the PCM to reset/shut down.

Urambo Tauro > jimz
12/22/2016 at 12:45

If that is indeed the case, I wonder why it’s not so common among other manufacturers.

Is this like an extra fail-safe to keep the PCM from low-volt/high-amp damage? I could see that as a positive thing, unless Ford PCMs are more fragile than others, thus requiring such a fail-safe.

jimz > Urambo Tauro
12/22/2016 at 12:55

the idea is that the PCM needs to stay running down to the worst-case cranking voltage in a car with a battery in reasonably good condition. other modules in the car (radio, etc.) turn off during engine cranking. if supply voltage goes below that then AFAIK the internal power supply can’t output enough power to keep all of the electronics awake. I don’t know the specifics of that car, but my assumption is that the supply voltage is just dropping below that threshold with a weak battery.

Urambo Tauro > jimz
12/22/2016 at 13:02

Yeah, that makes sense.

I’m not sure how low the voltage was getting on that battery during cranking. When they load-tested it at the parts store, the number they gave me was in CCAs. If I had tried to load-test it at home, I would have used my meter’s min/max feature to record voltage extremes while cranking.

TahoeSTi > Urambo Tauro
12/22/2016 at 13:27

If you keep having these issues check the ground wires to the block. Had to replace mine on my 95 after doing motor mounts. Seems to fix some of the battery related starting issues.....my new issue with it is after the 3rd start of the day I get hiccups under light load ( like going up a slight hill) Let off the throttle a bit or getting on it more stops it.