Jeep Won't Start: Starter Spins But Doesn't Engage Flywheel - JeepForum.com
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post #1 of 19 Old 01-10-2015, 11:15 PM Thread Starter
GeoffCornish
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Jeep Won't Start: Starter Spins But Doesn't Engage Flywheel

I've "lurked" quite a bit and learned from many of you over the past decade, but this is my first post, as I have a question of my own.

My 2004 Wrangler X is not starting. When turning the ignition, everything from the electronics system through the starter relay through the "spinning" sound of the starter seems healthy.

However, the engine is not responding at all... no movement and no sound of any activity beyond the faint "whirring" of the starter.

I pulled the starter out and took it to AutoZone, and they put it in the machine to test it, and it tested "good". I re-installed it, and replaced my battery (old one was on its last legs). After putting my new battery in, still no dice.

I don't have 100% confidence that the guy at AutoZone looked into every aspect of the starter's health. Could the starter have "tested" OK, but might the solenoid be shot? (Spinning but not extending / engaging with the gears to the flywheel?)

Does an AutoZone "starter test" check the solenoid, or does it only check the spinning in the guts of the starter?

Any advice is much appreciated. Not a mechanic (obviously), so forgive the clumsy phrasing. Thanks all...

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post #2 of 19 Old 01-11-2015, 12:09 AM
Knuckelhead
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Quote:
Originally Posted by GeoffCornish View Post

I don't have 100% confidence that the guy at AutoZone looked into every aspect of the starter's health. Could the starter have "tested" OK, but might the solenoid be shot? (Spinning but not extending / engaging with the gears to the flywheel?).
That is very possible, try giving the starter a whack with a hammer...

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post #3 of 19 Old 01-11-2015, 01:56 AM
ChrisTJ34
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Your starter is probably bad the gear is supposed to move forward and engage the flywheel. The solenoid just completes the circuit. Your gear isnt moving forward engaging the flywheel. Which is why you hear the whirling sound. Theres also a posibility it just needs adjustment but seeing as it worked before id say your starter is bad. Let us know what the problem was.
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post #4 of 19 Old 01-11-2015, 02:20 AM
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The starter motor itself doesn't engage until the solenoid moves the electrical contacts into place for engagement. Sometimes that engagement can happen without the starter gear contacting the flywheel (manual transmission) or flex plate (automatic transmission). Giving the starter motor a whack with a hammer can resolve the problem, sometimes, maybe...

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post #5 of 19 Old 01-11-2015, 07:29 AM
sangdigger
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Just go buy a new starter before it leaves you stranded and not one from Advance get a good one from NAPA or CARQUEST and you will be good
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post #6 of 19 Old 01-11-2015, 09:08 AM
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The starter gear (bendix) contains an over run clutch. This enables torque to be applied to start the engine, and when the engine starts the clutch allows the gear to spin faster than the starter allowing the gear to disengage. If that clutch starts slipping the gear can engage the flywheel but not turn the engine over. When bench tested it would appear good but as the gear doesn't have torque applied it's not something that would be obvious.

I've had this happen in the past. When it did the engine would fail to start sometimes. Not starting becoming more common. If this is what's happening in your case you may feel some torque released as the starter turns off, possibly with a small clunk. I rebuilt my starter with new bendix, brushes and solenoid. In the US it's easier to just replace it.
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post #7 of 19 Old 01-11-2015, 09:56 AM
Curly5759
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Jonny Jeep got it right. Bad starter drive.

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post #8 of 19 Old 01-11-2015, 01:58 PM Thread Starter
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You guys are great -- thanks for the advice. Was tied up earlier today but am about get back "on it".... I'll let you know, this evening, what the result is. Thanks again, all.
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post #9 of 19 Old 01-11-2015, 02:54 PM
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You have good advice here on the likely situation you have with the starter. I just thought I'd add a word about the testing done at Auto Zone and similar places. I use such places to see if I have a "bad" starter, but not to see if I have a "good" one. What I mean by that is that if they test it and say that it is bad, then it is definitely bad. But if they say it tests good, then it might be good. The problem is that they test to be sure that A) the bendix fires out, and B) the motor spins the bendix. They also receive a resistance reading, but in my experience the employees there don't usually have enough expertise to determine whether a visually operating starter has enough oomph to actually turn the crank. I actually had a friend take his starter to O'Reilly's on the way to meet me at his vehicle, and he watched the test being done. The employee told him that the starter was good, and my friend even watched the bendix fire out and spin. When he met me, I inspected the starter and found that the I could flick the bendix with my finger and it would spin freely. Needless to say the employee was surprised to see us return together, and purchase a new starter. Hopefully he realized that a quick manual check should be done in conjunction with the bench test.

Anyway, good luck with your situation.
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post #10 of 19 Old 01-11-2015, 08:21 PM
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This in addition to all the bits about the bendix. I think it is probably the bendix.

It could be the flywheel. You might have broken off or worn off a tooth. The bendix might go forward and not have anything to engage with. Simple enough to visually check with a mirror. If you've ever owned a kickstart dirt bike you might have noticed that the engine stops in the same position most (but not all) of the time. You would have noticed that you feel resistance of the kickstart pedal I'm the same position most of the time. Our engines like to stop in one of three positions most of the time. These three posititons on the flywheel take most of the abuse and wear. You can see it on a high mileage engine when your doing a clutch swap. Sometimes one would carry around a big bar and socket to manually turn the engine over a small amount so the bendix has a good tooth to engage with.

I have had the "turn the key and it whirs" once last winter. I deduced that my bendix was frozen in place as this was an extremely cold day. I pushed a small bbq camp stove under there and let it run for 10 minutes and that fixed the problem. Obviously not what you are experiencing but it's the first thing I thought of.

You have a manual, if you have a buddy you can still pull start it if you really need.

If you filter out everything that has bad spelling and grammar, you can believe 95% of what you read on the Internet.
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post #11 of 19 Old 01-11-2015, 11:50 PM Thread Starter
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Thanks, all...

I put a new starter in... and much to my disappointment, I got the same result. I took the new one out, returned it, and swapped my old one back in. One of the guys at AutoZone was much more car-savvy than the other guy (he was probably well ahead of the curve for auto parts retailers, when it comes to firsthand experience as a mechanic). He suggested it was likely a wiring problem. A bad connection may not be delivering enough juice to properly drive the bendix.

The teeth of the flywheel gear appear to be in good shape, and I am able to turn it, manually (not easily, but it does turn).

After putting my old starter back on, I visually inspected as much wiring as I could and jiggled all connections, and then hooked the battery back up. I turned the key and on my second attempt, it started up for the first time since Tuesday (and without hesitation).

I drove it to my mechanic's shop, shut down, and then had about 60% success with start-ups in his parking lot. A few of the "successful" attempts seemed to stutter within the first second of ignition (in the start-up process, NOT the sound of the engine struggling). It leads me to believe it is a wiring issue, after all of this.

The mechanic's son happened to be there, after-hours on a Sunday (he also has been a mechanic) and says it is not uncommon for wiring under the hood with Wranglers to have issues, since there is a little more space under the hood for muck, snow, grime and crap to be tossed around, compared to, say, a Buick.

I left it there and hopefully he'll pinpoint the issue. Replacing the starter was easy enough for my level of inexperience... but wiring issues quickly go beyond my level of comfort.

At least I don't have to pay for a tow.

Thanks again for your input. Can't help but learn by going through this / reading your comments....
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post #12 of 19 Old 01-12-2015, 12:13 AM
ChrisTJ34
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Well i have never herd of this being a wirring issue. Does anyone on jeep forum have a scientific explanation for this phenominon?
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post #13 of 19 Old 01-12-2015, 12:30 AM
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Possibly the feed wires to the starter or the battery ground cable have internal corrosion that have high resistance and wont allow the current necessary for operating the starter?

Sometimes normal operating current can operate the system, but with the high draw that the starter has it can fail to deliver the necessary current to drive the starter...

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post #14 of 19 Old 01-12-2015, 11:17 PM Thread Starter
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The mechanic, based on what I told him I did, said we basically did everything they would have done to troubleshoot it, and he recommended I take it to a locally-owned shop that specializes in automotive electronics (cars, boats, etc...). After 5 days of nothing, it is now starting 60% of the time on the old starter, so perhaps the wire-jiggling has things temporarily in a SLIGHTLY more stable state. I dropped it off at the other shop, and they seem confident they'll take care of me. I'll let you know how it all turns out (cost, etc.) and what their determination is.
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post #15 of 19 Old 01-13-2015, 08:44 AM
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I have a 2008 JK that is about 70% start ratio and did everything you did as well. I did find if I turn the key on without trying to start for a few seconds, then hit it, it will start 90% of the time. We've gone round and round on this one so now we just call that Jeep retarded.

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