thoughts, ramblings, and rants

4/29/2005

Why won’t a car’s starter work?

There was a time in my life many years ago when I wanted to be a mechanic, but for a variety of complex reasons, that dream was never realized to its full extent. I spent most of my late teenage years taking cars apart, and usually putting them back together: I loved it. I even had a mobile mechanic business for a short while in later years, but couldn’t make it profitable enough to live in the rising real estate of Southern California, and that’s when the “love” of working on cars passed. I remember this one guy who’d called me, asking for an over the phone quote for something specific. After giving him the quote, in oblivion he asked, “Will you do it for $5.00 less than ______ down the street?” There’s a definite downside to empathy, and I was already near the end of that business endeavor. Anyway, I still work on my own vehicles exclusively, but now that’s quite infrequent.

Coldforged.org tells us a story of his recent car troubles, which inspired this short and generalized post you’re now reading.

Why won’t a car start?
(Please keep in mind my explanation is inherently simplified)

Sometimes, the battery has lost its charge for a variety of reasons.

Sometimes the wiring of various parts of the car’s systems leads to increased resistance of current flow. Terminals sometimes corrode or work themselves loose.

Sometimes, the ignition switch fully or partly wears out. Most ignition switches are multi-pole, and when they work properly, they energize multiple circuits simultaneously. One of these circuits is the starting system.

Sometimes, the starter relay malfunctions. Usually, this doesn’t allow the passage of high-amperage battery current to the starter. Sometimes the relay’s contacts remain together after the ignition key is returned to the ‘run’ position. I’ve replaced a number of starter relays, they fail often.

Sometimes the starter itself wears out. Right now I forget the specialized name of the mechanism in the starter that extends the starter gear into the flywheel. When the ignition key is turned to the ’start’ position, this energizes the starter relay allowing battery current to flow to the starter, turning it. The unnamed starter gear extends into the flywheel’s ring teeth to start turning the engine’s crankshaft. When the ignition key is returned to the run position, the relay is supposed to close and the starter gear is supposed to retract an inch or two, disengaging it from the teeth of the flywheel, as well as to stop turning.

Sometimes, when the internal starter mechanism that extends and retracts the starter gear from the flywheel wears out or becomes corroded, or the relay malfunctions, after the key is returned to the ‘run’ position because the engine has started, the starter gear remains engaged in the flywheel. In this condition, the engine is turning the starter beyond its normal speed, because the car’s engine is forcibly turning it. You don’t want to drive a car with the starter gear still engaged in the flywheel. It’s not designed to turn that fast, there’s too much stress on its bearings. A non-normal sound is usually audible. If you hear this, turn off the engine immediately!

Initially, ColdForged’s starter relay likely had pitted contacts, or some similar malfunction that wouldn’t allow current to pass from the battery to the starter. Perhaps wiring terminals were loose or some wires had too much resistance. It’s really not possible to say precisely without seeing the car during the initial malfunction. Complicating the issue was the intermittent nature of the car’s starter problem, sometimes during troubleshooting, everything works fine. A mechanic’s experience of what normally wears out in the starter system comes in handy.

When ColdForged drove his/her car to the parts house, I think the starter gear was extended into the flywheel, this literally killed the starter, and likely caused all the smoke he/she saw and smelled.

(I don’t think or read about ‘this stuff’ as much as I used to, my terminology is passing from memory)

File: — Ken L. Klaser @ junkyard 4:14 pm PST, 04/29/05

8 Comments

  1. Grease monkey showoff! :D.

    But seriously, thanks for the insight. Would that have killed the flywheel too, Ken? They didn’t replace it unless — and I’ll unashamedly expose more idiocy here — it’s part of the actually starter.

  2. Hi Coldforged! No, the flywheel isn’t part of the integrated “starter” mechanism you would purchase at a parts house. The starter mechanism does have a pinion gear, that when extended (because the ignition key is in ‘the start’ position) meshes with the flywheel’s ring gear. The ring gear might be damaged, but if your car starts okay, I wouldn’t worry about it too much. Your mechanic likely made a visual inspection of the flywheel ring gear when they removed and replaced the starter.

    In a manual transmission, flywheels are heavy, large diameter disks usually made of cast iron which the clutch bolts to. An automatic transmission doesn’t have the same type of flywheel, but it does have a flat, metal plate with a ring gear, or a torque converter with a ring gear. The flywheel is bolted securely to the transmission side of the crankshaft. The ring gear is at the outer edge of the flywheel, it’s essentially a hardened steel ring with machined teeth, and is usually pressed tightly into place. When the starter pinion gear meshes with the ring gear and turns, the flywheel turns the engine’s crankshaft. Flywheels and flywheel ring gears are located between the engine and transmission.

    Over time, it’s normal for the ring gear to wear some on the starter side from the action of the starter pinion gear extending to mesh with the flywheel ring gear. When the starter is removed, it’s hard to see the ring gear through the relatively little hole the starter bolts into. To see all the ring gear’s teeth would require slowly turning the engine’s crankshaft while each section of it comes into view, or to separate the engine from the transmission. It’s a lot of labor to separate the two—>$$$. That’s why if it seems to work okay, now that your mechanic fixed it, I wouldn’t worry too much about it.

    If the transmission is ever removed from the vehicle then it makes sense to remember this incident and check it again. At that time, the entire ring gear will be visible at once, without needing to peer through the ‘hole’ where the starter bolts and needing to slowly turn the crankshaft while viewing each small section.

    If cranking sounds normal when you first start your car several times, then it’s probably fine. If a ring gear tooth is, or teeth are, missing, it’s a problem. During a start, once the starter’s rotating pinion gear reaches the missing teeth of the ring gear, it would no longer mesh and would stop turning the flywheel, and the starter would simply spin. Another type of starting problem occurs when you try to start the car and it’s followed by a loud high-pitched noise, which is the sound of the starter spinning without having engaged the ring gear. Repeating the effort a time or two might result in a successful engagement and engine start. This would be ‘one’ typical symptom of worn or damaged ring gear teeth. It’s also a symptom of the pinion gear not extending fully.

    If you hear odd noises when first cranking the car, or it takes several times turning the ignition key to the start position before the starter engages the flywheel leading to normal cranking sounds, then the ring gear likely needs to be visibly checked again and possibly replaced, given that your new starter is likely in good condition.

    Hope this helps!

  3. Thanks, Ken! Excellent description… maybe you should have been a mechanic.

  4. Which one is more likely to wear out the starter or the flywheel? I have a 99 cougar that is experiancing the same type of problems, a whirling noise when i start the car. It used to only do it once every few months, now it seems to be once a day, please advise as to what I should do first. Fix the starter, or the flywheel?

    2.5l Automatic Trans 6cyl 99 Mercury Cougar

  5. The starter is more likely to be the culprit. Inside the starter is a Bendix gear, (which I couldn’t remember the name of when I wrote the above). It’s another mechanism that extends the starter’s pinion toward the flywheel’s ring gear. Bendix gears wear out frequently; given your symptoms, I’d suspect this part is wearing.

    This next possibility doesn’t seem as likely with your particular symptoms, but it bears mentioning in this thread.

    It’s also possible the starter is mis-aligned: Mating surfaces between the starter housing and bell housing can be damaged or dirty. I’ve heard of people shimming the starter’s mating surface at times, but I’ve never had to do that (yet). If you have any questions, it’s a good idea to buy a factory service manual, if one is available, and follow their various procedures carefully. I’m certain there’s a specification for pinion-to-ring-gear clearance, as well as how far the starter extends into the flywheel. The point is that measurements can be made.

    When/if you have the starter out, get a mirror, a good light, and probably a helper. If you can’t get your eyes close to the hole the starter came out of, get a mirror mounted on the end of a telescoping handle. With the battery disconnected (for safety–it should be disconnected before the starter is removed), have the helper slowly turn the crankshaft with an appropriate wrench, extension, and socket on the bolt retaining the front crankshaft pully. Rotating the crank is much easier with the engine’s spark plugs removed. Important: Make sure the crankshaft is rotated in the direction it normally turns. Visibly check the ring gear through at least 360 degrees of crankshaft rotation. Check every ring-gear tooth! Some slight wear is normal on the starter side of the ring gear; if there’s too much wear, it could cause meshing issues.

    Don’t assume that wear patterns are symmetrical across all teeth, engines tend to stop in similar places relative to crankshaft rotation due to the compression that occurs in the cylinders. If you’re not sure what to look for, get someone who does! Good luck!

  6. Why won’t a car’s starter work?

    [Source: Conscious Junkyard] quoted: During a start, once the starter’s rotating pinion gear reaches the missing teeth of the ring gear, it would no longer mesh and would stop turning the flywheel, and the starter would simply spin. Another type …

  7. Wow, I’m pretty impressed with your knowledge so far. I’m having similar problems on a V6 1999 Cougar. The starter will just spin and not make contact. I took off the starter and took it to Autozone to have tested. They said that it extends fine and spins fine. So I checked ring gears and the visible teeth on the fly-wheel and everythign seems fine. Doesnt seem like they are rubbing and missing. Taking the word from Autozone that it works fine I put the started back in, and I’m still having the same problem. The surface was clean, I made sure the bolts were tight, and still same problem. Could autozone’s test possibly give a bad result? Or should I try somethign else?

    thanks.

  8. “The starter will just spin and not make contact.”

    You need to understand why the starter just spins and doesn’t “make contact” on your specific vehicle (which I’m not familiar with). If the pinion gear doesn’t extend—or extend far enough—and mesh with the ring gear the starter could just spin: there’s no load on the starter in this case.

    The person who ran the test claimed the bendix and pinion did extend on the bench with “bench wiring” and “bench voltage”. Maybe it worked right on the test bench once, but it’s possible there’s an intermittent issue of some kind, or some test element is different between the bench and your vehicle. Did the pinion gear look worn next to a new one?

    Perhaps there’s an alignment issue when it’s installed on your car. Is it the correct starter (engineering dimensions) for the application? Is the ring gear out of it’s engineered placement? Two mechanical measurements I would want to make: mating surface (surface the starter bolts to) to ring gear (beginning of teeth considering thrust direction), and starter mating surface to the end of the extended pinion gear teeth. From these two measurements I could discern whether there’s likely to be a mesh between the two by inference from the overlap measurement, or difference between the two, assuming it is the correct starter and pinion for the application.

    It’s been my experience that if voltage is low, a working solenoid relay will click but will not result in a starter that spins. However, I’ve read of low voltage situations that will result in a spinning starter, but one not spinning fast enough to thrust the bendix and pinion out, and if the ring and pinon gears aren’t meshed, then there’s no load on the starter. Causes of a low voltage situation could be loose or corroded connections, a bad (or discharged) battery, battery and starter cables that because of their age have increased resistance to current flow, or perhaps inner solenoid contacts that have become pitted with use and therefore offer high resistance to current flow (lowering voltage at the starter motor under attempted cranking).

    One way of approaching these test issues are with factory specifications (manuals are handy) and various instruments and measuring tools to rule out working elements of the system. Another way is to swap suspect parts out with another part that is believed to work, but, that can get expensive when you start buying parts you don’t need because you guessed incorrectly which part was causing the problem.

    edited on 2/1/2006 to add:

    I’m closing down this thread to further comments. This last comment I made to a degree repeated information in the post itself, so the logic of adding additional answers has become, for me, somewhat circular, as I have little additional information to add.

    If you are having problems with your particular car starter, there is a lot of good information online. If you are still unable to figure out how to get your car to start because something is wrong with the starter system, consider hiring a technician.