Testing starter draw on car:
 

I did a web search on this and all I'm getting is results about parasitic draw, i.e. bad starters draining batteries while parked. I have a friend whose starter cranks slowly and I was sure that her battery was dying until I tested the battery with my load tester and it passed more than once. I had her start the car with my multimeter reading the battery voltage and it dropped to about 9-10V while she cranked the starter. I have no idea whether this is normal, first time I've checked it like that.

I suspect that her starter is drawing too much juice and will die at an inopportune time. Of course, I know that I can remove the starter and have it tested somewhere independently from the vehicle but I'm busy as hell and would love to test it on the car.

My knowledge of auto electrics reaches to testing batteries and alternators with my multimeter and load tester and finding bad grounds occasionally, beyond that I'm lost.

So...I do know that it's all about amperage with things like starters but I don't know how many amps it's supposed to draw or really how to test that. I'm sure it's on my multimeter somewhere. Awaiting smarter electric people. :)

Car is a 2009 Suzuki and owner is going through a tough time so trying to help if possible without just throwing parts at it or putting it in a shop. TIA.

I do not understand how a starter can be a parasitic draw.

I would check the cables, and the ground connection.

Try starting the car while jumping it. It may be your assessment of the battery that's the problem.

Or the starter itself.

Older starters without the gear reduction of many modern starters do draw a lot of current, I'm thinking hundreds of amps is normal. You possibly already have done this but try removing the clamps at the battery and make sure they are not corroded clean and replace. Are you checking voltage from the battery post or from the cable clamp? What type of load tester are you using? If you knew exact reserve power of the battery you could work out starter current using voltage drop.

1990C4S, I have read about parasitic current from material building up in the solenoid contact area.

Same thing applies to the battery connection to the starter and the ground. Denis is an accomplished mechanic. I think he just wants a clamp-on amp meter for DC amps.

The only test that I'm aware of is having someone start the car and watching the voltage. Unfortunately that's not a test of "the starter", it's a test of "the system." The system is the battery, cables, starter, and potentially even the motor itself.

If the voltage drops too low during starting, that could be a bad or going-bad battery (too few CCA/CA). It could also be a going-bad starter (too much draw), or bad cables or connections (insufficient current getting to the starter).

Is the cranking speed your only concern or was there something else? It does look like Suzuki had starters with planetary gears at that time, they do spin the engine much slower than older starters.

Me neither. Maybe might post wasn’t as clear as I wanted but the parasitic draw thing was what I got for search results when I put in “starter draw.” I suck at Google.

What I have is a starter that draws a lot when engaged.

Thanks for that info, how did you get it? Trying to improve my search skilz.

I just looked for some pics showing internals. I do not know what year manufactures started using planetary gear starters. I was surprised years ago when I changed the starter solenoid on my 2011 2500hd and there was one in there.

$25 buys you a 400 amp non-contact Clamp-On Ammeter for DC circuits.

https://www.amazon.com/gp/product/B08JSQZTRF/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&th=1

If you're going to measure the starter amperage draw you will need to know the expected result...sort of like your voltage drop measurement.

Apparently 10VDC is the cut-off line for a failing battery or a bad starter. I would suspect the battery first.

That meter above is amazing value, assuming it works...

I suspect the battery.
Here's the amp clamp i've got.....highly recommend
https://www.amazon.com/dp/B08MTCMWLB?linkCode=ssc&tag=onamzpineholl-20&creativeASIN=B08MTCMWLB&asc_item-id=amzn1.ideas.UKPVIGM4POWZ&ref_=aip_sf_list_spv_o fs_mixed_d_asin

Thanks, guys. I have a pretty good battery load tester, it’s completely analog with a meter on it that tells voltage and drop when you hit the load button. You can burn yourself really well if you’re not careful after using it because it has coils inside that heat up.

That looks like a decent tool for the casual user.

Did you solve the problem?

Did you do a draw test on the battery? There might actually be a draw but the starter would not be the cause of the draw. You can test for draw by disconnecting the cable and placing your MM between the cable and terminal if it registers voltage there is a draw. If there is a draw you can start pulling fuses until the draw goes away and that circuit is the culprit.

After reading all of the replies to this thread, I'm not sure if there is a serious problem. Maybe just a starter that draws a little more than I'm used to and turns slower. It always starts the car pretty quickly. I did clean the battery terminals, the positive make a lot of corrosion for some reason.

I have not done a general draw test on the system yet but I will. The battery does not seem to be getting drained while parked, just the slow starter mentioned previously.

Thanks again for all of the input. :)

She must be hot. There's a thread for that.

Hi Denis! I hope all is well with you.

The following is a real-world example of an engine starting.

http://forums.pelicanparts.com/uploa...1715705480.jpg

There is an initial, large draw of current from the battery (often in hundreds of amps) to begin the rotation of the engine. In conjunction, the battery voltage will drop significantly, as you noticed. After the initial rotational inertia is generated, the amperage draw drops off but current draw is still significant (heating of the starter!). The pulses in the current plot show the compression of the cylinders as the engine rotates. The engine begins to start, current load drops and the battery begins recovery; the engine then runs.

Many factors effect the starting of the engine. Health of the starter, battery, engine, (cold) temperature, type of oil, etc. I'm sure many people can offer a better and more detailed explanation, but this is the very basics.


Lee