Scoping a starter circuit, revisited
A few months ago a gentleman asked about scoping a starter on an intermittent no start. He asked whether or not any useful information can be had. Myself and a few others said no.
Still others chimed in and said,that in fact there is something you can look for: starter current reflecting solenoid engagement.
This intrigued me. Id never heard of or thought of this myself, so I decided to do some homework.
Ive scoped around 25 vehicles to try to establish a baseline.
Theses pictures are a close up of initial starting current of the last vehicles I checked
All of these vehicles started and ran every time I scoped them, however one of these vehicles was in for an intermittent no crank,no start.(which I was able to reproduce later)
Care to guess which?
Pictures are as follows:
Capture 5. No pintle/contact movement? Capture 3, I kinda interpret as being a weak solenoid, with an contact engagement that flutters back and forth. Looking forward to the answer
Kevin- All of the captures were taken on vehicles that started and ran. Ill check back in the AM and well all have a discussion.
I guess that eliminates number 5, leaving number 3 as the culprit. I think its interesting that the Outback's starter solenoid reached it fully saturated state before there was any contact movement, or perhaps its simply not visible in the waveform. Was that a remote mounted design? (Not physically attached to the starter)
Kevin- It was not remote mounted. I have another Subbie in right now(2011 Outback),Im going to check real quick to see if its the same.
Kevin- 2011 Outback. I guess its a characteristic of some Subaru starters
According to what Marlin Good posted over there, that two or more bumps on the solenoid can cause a no start, I would have to say that 3 is bad. Picture six also has more then 2, I myself am not convinced from the testing I've done it seems to inconclusive, to many cases of cars with out an issue that seemed bad.
Lazer- Can you elaborate on the testing you have done? How many vehicles? I would not randomly use this test to condemn a starter, however if the complaint is intermittent no crank, no start, I think it can be a good indicator…
Eric- He only briefly touched on this subject, and if one were to only read that thread and follow that logic, then all of the vehicles here(execpt the Subaru) have failing starters….
Rudy, I agree, all of those starters except for the Subaru have a problem with the starter, the starter solenoid specifically. What those little up down spikes show are a poor connection at the starter solenoid contacts. The contacts are not making a good connection, they are bouncing and arcing trying to make a connection. While that might not make a noticeable starting problem it does show…
Eric- Youre not zoomed in as close as I am. Most of my captures look like yours when I am zoomed out as far as you are. Of the 25 vehicles I checked, I find it hard to believe 24 of them have bad starters. Additionally BOTH Subarus I checked had similar patterns. So again, only those 2 vehicles were good? Finally, the remanufactured starter I installed also had “bouncing” These are the same…
I guess I don't know how to read the vertical scale on your scope, I thought those waveforms were showing 600 - 700 plus amps. Even so, I stand by my statement about the problem. How far do you want to zoom in? Here is the 2011 Corolla, left capture shows the full current inrush, right capture is zoomed in on the initial starter solenoid turn on. I can zoom in further if you would like but it…
Eric, you and Rudy are zooming in on different spots on the waveform. Rudy is talking/zooming on the in-rush current (600+Amp spike) and you are zooming in on the solenoid turn on part (30 amp). I believe Rudy is correct, when zooming into the starter current spike (600-700A spike), 95% of the starters will have a few oscillations. I’ve seen it on new starters as well. I believe it’s a problem…
Octavio, Look at Rudy's reply just a couple up from here, he states that I'm not zoomed in as close as he is. In that reply he shares his full size captures. Current draw will change with the spikes showing on initial startup of the starter motor, this happens on the starter motor just like on a fuel pump motor, the brushes moving across the spaces or insulation in the armature. I don't know…
I forgot to add this example, a 2006 Honda CR-V with a faulty starter, starter waveform on the left, look at the bad motor. I disassembled the starter and found the brushes worn out and grinding into the commutator. The starter worked and sounded normal, just cranked a little slow, sounded a little off. Check out the solenoid turn on, zoomed in on the right side, picture…
I just had a 2017 Kia with 40k in. Scoped the circuit and it had 2 bounces in it. I am unconvinced all of these cars Ive checked have bad starters. I still think it is a characteristic of these starters, and isnt an issue unitl it becomes excessive.
Hi Rudy, Instead of testing only at the power cable on the starter, have you also tried just the starter signal lead. I am curious if that would indicate an issue. I ask this because I recently ran into that on a Ford. The starter was having issues pulling in the solenoid and cranking. The replacement starter actually came with a replacement pigtail that had to be installed. Out of curiosity I…
Are you checking the voltage at the same time you check the current draw? Did you watch the video I linked about testing the starters? They mentioned a minimum battery voltage on the scope capture. I've seen the bounces when the battery voltage drops too low. I don't like to see the battery drop below 8 volts during cranking, but at the same time if it doesn't drop below 9.5 volts I look for…
I always like to look at current and voltage together. If the starter cranks poorly but I see it pull 700-800 amps, I'm not worried about any voltage drops. If the starter current is low and the battery voltage doesn't drop a lot, then I'm looking for resistance in the circuit. Etc. Etc. Basically look at the current /voltage and apply a logic chart to hone in on the fault
Eric I did hear the guy in the video you posted state “it's kind of rare to turn on the solenoid with 1 attempt” ….
1998 Caravan. They always burn the solenoid contacts.
I'm gonna guess bottom left. (Not sure if it's meant to be #3 or #5. Either way, I'm very interested in seeing what results you found
On second look. I think it's the top right. What's going on with the ripping effects after the start up event? It's also happening to a lesser extent on the lower right capture.
My guess will be 5 with no small hump before the in rush current, but im no expert. Let us know thanks
#3 with the bouncing solenoid? This may be of interest: youtube.com/watch?v=X-974J…
2011 Toyota Corolla 1.8, known good The blue channel is the battery volts, cranking at 10.63v The red channel is the engine block ground voltage drop to battery negative at 311mv The green channel is the starter amps and when the engine starts, the alternator is charging at 100 amps The black channel is the starter solenoid. The peak amp draw is 23.7 amps and the hold section measures 8 amps
I also believe starter #3 due to multiple/indecisive draw. I was on Aeswave. Com a while back and looking at their cool tools and saw they had some sort of switching box(signal router) with a lot of test leads that caught my eye. They offered some videos on what it does, which one was a starter system check on a slow crank suburban if memory serves. Seemed like a good deal, especially…
where is scope hooked up PCM to starter relay ? i say both Toyota's a loose screw arcing or a say pull in windings /hold in windings no idea ….following ! The GM who knows could be Bump starts system out of the drivers hand unless low on fuel, maybe its a remote start ????…..What other starter Mumbo and not my AMC 360 going KuHhhhiiinnnngggggggg in a rain storm….Thread leads us to the Silverado…
As many of you correctly guessed #3 the Caravan was the culprit. One of the things Id found was that 24 of the 25 vehicles I looked at had some kind of bouncing around in the current wave form. The Subaru here was the only outlier. So in my opinion it is normal to see some activity in the starter current. Id go so far to say that 2, 3, or even sometimes 4 humps is normal. I'm guessing a lot…
Rudy I agree with you the caravan was too many, I was saying I've seen a few with 4 bumps & the car never had a problem, so I had no baseline to say what's bad or good. I will defiantly do more testing because if I would have intermittent no crank and see the waveform like the caravan I would also say it's bad. Thanks for bringing up the good topic!
Rudy, I think this was a great experiment showing that between “known good” and “known bad” there is a gray area all the way from “known good enough” to “known pretty bad”. What exactly that area is sometimes requires statistical analysis (for example, linking the length of hash in the waveform to the probability of no-start), which is fun for mathematicians, but not fun for pretty much anyone…
I was gonna say “the Honda”. :-) Feliz año nuevo mi hermano
Interesting study, I recently also had an intermittent no start on a 12 Accord. Simply placed amp clamp on battery and solenoid and found some interesting results. Compared it to a known good (different vehicle) and you can see a huge difference in solenoid activity. I may not know exactly what I was looking at but I could tell it was off. Blue cranking amps and red i solenoid. Pic 1 is bad, pic…
Oh, and if you really want to see what your scope can tell you when testing a starter, check out this Pico Training web page. Don't forget to download the Pico file at the bottom of the page, it has all the math formulas you need to perform the test, and you told your teacher you'd never use math once you were done with school! ;-)
Isn't that also the cranking compression test if no math ?