# Auto experts - what's wrong with my starter motor? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [February 17, 2018, 11:04pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024 "2018-02-17T23:04:12Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Roderick\_Femm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/roderick_femm/32/14875_2.png) [@Roderick\_Femm](https://boards.straightdope.com/u/Roderick_Femm)\ **Post date:** [February 17, 2018, 11:04pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/1 "2018-02-17T23:04:12Z")
2000 Infiniti I30, 84K miles, since retirement it only gets driven once or twice a week, for a few miles. Presumably as a result of that driving frequency the car is harder to start, it cranks over several times, doesn’t start, we turn off the key. Do that anywhere from 2 to several times. When it starts it shoots out a lot of dirty looking exhaust. The mechanic says this is normal when the car is sitting around all the time. Now it is doing something new, after a couple of starting attempts it just stops turning over. This actually happened at the mechanic and he was able to get it to turn over again by tapping on the starter motor. Then he said we need a new starter motor. But it was late (he had done a brake job on the car and hadn’t had any problem starting it) and I needed to go home. The next morning it did the same thing and I was able to get it to turn over again by tapping on the starter motor. TL;DR starts here: So, my question: is this more than a loose connection? What’s going on inside the starter motor when I tap it to get it to go again, such that the whole thing needs to be replaced? Normally I trust this mechanic but it seems odd that very lightly tapping on something with a hammer would make it work again. I just want to understand how this works before I pop for a new starter motor. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 17, 2018, 11:24pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/2 "2018-02-17T23:24:13Z")
> [@Roderick\_Femm](#): > > 2000 Infiniti I30, 84K miles, since retirement it only gets driven once or twice a week, for a few miles. Presumably as a result of that driving frequency the car is harder to start, it cranks over several times, doesn’t start, we turn off the key. Do that anywhere from 2 to several times. When it starts it shoots out a lot of dirty looking exhaust. The mechanic says this is normal when the car is sitting around all the time. > > Now it is doing something new, after a couple of starting attempts it just stops turning over. This actually happened at the mechanic and he was able to get it to turn over again by tapping on the starter motor. Then he said we need a new starter motor. But it was late (he had done a brake job on the car and hadn’t had any problem starting it) and I needed to go home. The next morning it did the same thing and I was able to get it to turn over again by tapping on the starter motor. > > TL;DR starts here: So, my question: is this more than a loose connection? What’s going on inside the starter motor when I tap it to get it to go again, such that the whole thing needs to be replaced? > > Normally I trust this mechanic but it seems odd that very lightly tapping on something with a hammer would make it work again. I just want to understand how this works before I pop for a new starter motor. [this is what it looks like inside one.](https://i0.wp.com/autosystempro.com/wp-content/uploads/2013/06/Solenoid-operated-starter-has-the-solenoid-mounted-directly-on-top-of-the-motor.jpg) when you turn the key to request engine start, the solenoid mounted on top of the starter motor does two things: 1. the plunger moves the shift fork outward to engage the pinion gear with the engine flywheel’s ring gear, and 2. a contact disc/plate on the other end of the plunger acts as a “switch” to connect the battery cable post to the internal wire sending current to the motor through carbon brushes. what happens when a starter fails to turn over and “tapping” it gets it working again, a couple of possible reasons, 1) the contact plate or terminal posts in the solenoid are pitted and eroded/corroded from arcing (they have to conduct several hundred amps of current and make big sparks when they do) and/or 2) the motor brushes are degraded or contaminated, or there’s a build-up on the commutator. tapping it briefly “breaks through” these and lets them conduct current again. short version- starters are cheap, just replace it. ---
**Author:** ![Roderick\_Femm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/roderick_femm/32/14875_2.png) [@Roderick\_Femm](https://boards.straightdope.com/u/Roderick_Femm)\ **Post date:** [February 18, 2018, 4:03am UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/3 "2018-02-18T04:03:02Z")
OK, that all makes perfect sense, thank you. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 18, 2018, 1:19pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/4 "2018-02-18T13:19:28Z")
as for your other problem (multiple attempts to start and sooty exhaust) is the check engine light on? that’s not normal behavior. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [February 18, 2018, 6:32pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/5 "2018-02-18T18:32:08Z")
Some Lucas starters from the 1950s and 60s had a square end on the motor shaft that you could put a wrench on and give it a nudge. Hey, if you can’t make it work all the time, at least make it easy to fix. Dennis ---
**Author:** ![Roderick\_Femm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/roderick_femm/32/14875_2.png) [@Roderick\_Femm](https://boards.straightdope.com/u/Roderick_Femm)\ **Post date:** [February 18, 2018, 8:24pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/6 "2018-02-18T20:24:04Z")
> [@jz78817](#): > > as for your other problem (multiple attempts to start and sooty exhaust) is the check engine light on? that’s not normal behavior. Perhaps you missed the part where the car is only driven once or twice a week. The mechanic said it was common under those conditions. The sooty exhaust returns to normal exhaust after a couple of seconds. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [February 18, 2018, 9:40pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/7 "2018-02-18T21:40:48Z")
Sitting for one week should not cause a lot of sooty exhaust. Your car has other issues. It also shouldn’t take that long to start. It sounds like your fuel is draining into your intake system and slightly flooding the motor. ---
**Author:** ![Roderick\_Femm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/roderick_femm/32/14875_2.png) [@Roderick\_Femm](https://boards.straightdope.com/u/Roderick_Femm)\ **Post date:** [February 20, 2018, 6:17pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/8 "2018-02-20T18:17:20Z")
> [@jz78817](#): > > short version- starters are cheap, just replace it. You know, I really appreciate your information, and we did replace the starter, and the car starts much easier now. It doesn’t need to turn over so often even when it’s cold (not sure why a new starter motor would have that effect, but it’s all good). However, a new starter motor cost $288 plus $140 for the labor to install it plus tax. So over $450. This just after I had spent another $420 on a service, general safety check, and resulting new brake pads and rotors (I think that’s the right term) in the back. So no, not so cheap. Useful, even necessary, but not so cheap. Remembering that this is San Francisco, do I need to find a new mechanic? Am I being overcharged? ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 20, 2018, 7:02pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/9 "2018-02-20T19:02:25Z")
I’m going to guess they installed a brand new starter. remanufactured ones retail for around half that. ---
**Author:** ![Roderick\_Femm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/roderick_femm/32/14875_2.png) [@Roderick\_Femm](https://boards.straightdope.com/u/Roderick_Femm)\ **Post date:** [February 20, 2018, 10:20pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/10 "2018-02-20T22:20:23Z")
No, actually in rather faint print on the invoice/receipt it says “REMAN STARTER.” I don’t mind them taking some markup, but if they took 100% markup that’s a bit irritating. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [February 20, 2018, 11:03pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/11 "2018-02-20T23:03:08Z")
$140 sounds good/unsurprising for starter swap labor–even $140/hr–for SF. NAPA online lists starters for your car at $122 - $193 for generic remanufactured part You don’t need a new mechanic, you need to tell your friends about this one. 😉 **jz78817** –thank you for the detailed explanation about tapping the starter. I’ve known that trick for a long time but resigned to just knowing what to do and not what it does. ---
**Author:** ![GottaBeMeh](https://avatars.discourse-cdn.com/v4/letter/g/57b2e6/32.png) [@GottaBeMeh](https://boards.straightdope.com/u/GottaBeMeh)\ **Post date:** [February 20, 2018, 11:10pm UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/12 "2018-02-20T23:10:02Z")
> [@HoneyBadgerDC](#): > > Sitting for one week should not cause a lot of sooty exhaust. Your car has other issues. It also shouldn’t take that long to start. It sounds like your fuel is draining into your intake system and slightly flooding the motor. If he’s making several unsuccessful attempts at starting, then there will likely be a bit of un-burned fuel hanging around on the cylinder walls. Thus the black smoke when it does finally light off. That part is normal. It’s the not-starting part that isn’t. But he says it starts more quickly now with the new starter which is quite believable since a starter in the condition of his original one was probably simply not able to spin the motor as fast. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [February 21, 2018, 12:22am UTC](https://boards.straightdope.com/t/auto-experts-whats-wrong-with-my-starter-motor/809024/13 "2018-02-21T00:22:04Z")
> [@GottaBeMeh](#): > > If he’s making several unsuccessful attempts at starting, then there will likely be a bit of un-burned fuel hanging around on the cylinder walls. Thus the black smoke when it does finally light off. That part is normal. It’s the not-starting part that isn’t. But he says it starts more quickly now with the new starter which is quite believable since a starter in the condition of his original one was probably simply not able to spin the motor as fast. Yes I saw that and realized exactly what you are saying. I don’t see slow turning starters as often as I did 30 and 40 years ago.