Starter motor current capture

Hi everyone, I'm looking for a second opinion; I'm a DIYer, so I don't have as much experience looking at captures as many of you probably do.

I have a 2001 Honda Civic HX, and my wife reports that it has been having problems starting. I finally experienced it myself the other day, and it didn't "feel" like a battery; more like something "giving up" intermittently. I cranked and at first got almost nothing as far as the engine cranking over goes. I turned the key back and tried again, and it then started. Most of the time it starts just fine.

I have a starter current capture from November of 2017 when I was just getting my feet wet with oscilloscopes, using a pico 2405 to compare against the capture I got today using a pico 4425.

In the November 2017 capture, the "sawtooth" pattern looks pretty much like you'd expect. Today's capture has a bit of a dropout just before each "up-stroke". My best guess is that as the load is changing on the starter, something is moving inside, perhaps worn bearings... causing a very brief open just as the workload is starting to increase.

Anyways, the car has 254,000 miles on it, and the starter is the original. So I wouldn't feel bad about replacing the starter considering it's age, but I really don't want to be a.... <ahem> parts changer.

I'd really appreciate it if someone with a little more experience than myself could weigh in and offer a second opinion.

Thanks,
Curt

PS - I had technical difficulties with my 2000 amp current clamp (dead battery), so there was some excessive cranking while troubleshooting that, so the car battery might appear a bit lower than normal.

Here are a couple screenshots. I also found a capture from June of 2020, where you can see the downward spikes just starting to develop.

Thanks for posting the captures. I definitely see the drops in the cranking current that you're talking about. That's not good, but I've definitely seen worse.

What caught my eye was change in the starter solenoid contacts between 2017 and 2022 (which is really cool that you saved, BTW). This is zoomed in on the beginning of your 2017 capture:



There's only one little 'bump' in the current before the current in-rush occurs and the motor starts turning. Now for your 2022 capture:



There's three bumps there before the motor starts turning. From what I'm told, that's the starter solenoid contacts physically 'chattering'. Making contact, breaking it, making contact again. This represents a failing starter solenoid, and perfectly accounts for an intermittent no crank concern.

That's my take, anyway. :silly: I'd love to hear how others feel about it.

Thanks so much, Tyler. I didn't even think to zoom in on the solenoid "inrush", but that makes a lot of sense. I will be ordering a new OEM starter from Honda this afternoon, confident that I'm not replacing a "working" part unnecessarily.

Thanks,
Curt

No problem, Curt! If possible, it'd be great to see an after waveform of the replacement starter.

I only learned about the starter solenoid aspect of the waveform about six months ago, but it's worked out pretty well. I took this waveform from an '02 Subaru Outback last week, complaining of an intermittent no crank:



This is probably one of the worst examples I've seen so far. :silly: The very next time I went to start the engine, it wouldn't crank.

Tyler wrote:

No problem, Curt! If possible, it'd be great to see an after waveform of the replacement starter.

I only learned about the starter solenoid aspect of the waveform about six months ago, but it's worked out pretty well. I took this waveform from an '02 Subaru Outback last week, complaining of an intermittent no crank:

This is probably one of the worst examples I've seen so far. :silly: The very next time I went to start the engine, it wouldn't crank.

Not ment to hijack the thread, just want to share a curiosity: what do you think about these waveforms?

Juergen putting me on the spot with a pop quiz. :woohoo:

If I had to take a WAG, I'd guess the starter motor was binding internally? That might explain why the initial blips of current are higher than the in-rush current.

There was actually nothing wrong with the starter itself. The crankshaft sensor went crazy while turning the starter,afecting the v oltage and ampclamp readings in a peculiar way while multitriggering the coil.....Rerouting the ampclamp cable away from the HT lead cleared up this reading.In the pictures you´ll find the glitches coincide with secondary ignition events. Once started the car would run fine...

@Tyler - I will definitely get a capture after the replacement and share it. However, it'll be a couple weeks, as the online Honda dealer says they don't expect it to ship until August 17th.

Hello everyone,

The new starter arrived from Honda today, and I just finished installing it. At first glance, I saw the "dropouts" again at the bottom of each sawtooth, and some of the same "solenoid chatter". So I immediately looked to make sure I didn't install the old one back into the car. I did not.

But taking a closer look I do notice that there isn't as much hash around the dropouts now, and the starter is using noticeably less current, so that's good.

As far as what we're calling solenoid chatter - I'll be paying close attention for the next couple weeks, to see if there are any "uh-oh" moments when we turn the key. If there are, I might need to check the starter cut relay, or the clutch interlock switch.

Thanks,
Curt

PS - attached is the new capture, with the one from two week's ago overlaid with it. Also an screenshot of the capture. (how are you guys attaching the pictures in line with the message?)

Thank you for the feedback Curt!

Once you uploaded an image there pops up an option to insert it into the message body, it lterally says insert.

Testing...



ah-hah! it works! I was looking for it in the group of icons above the text box. Thank you.