C172M Starter Won't Engage

C172M Starter Won't Engage

RE: 1973 C-172M, Lycoming 150 hp, O320 E2D

Problem: When I turn the key to start the engine, it sounds like the Starter motor spins yet the prop does not turn. 

This started happening infrequently awhile ago and I only needed to move the prop to a new position and it would start.  I got stuck in Myrtle Beach, SC last Friday, because I couldn’t get the starter to engage not matter how many different prop positions I tried.  It was late at night and nobody around to help.  I had to leave the plane there and wait for Maintenance on Monday.

I guess it could be the clutch on the starter, but don’t know.

Anyone have any ideas and could recommend a good starter in case this one is shot?

P.S. Where do you go to learn to start the engine the old fashioned way?  (I'm not sure I would be brave enough to do it.)

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Re: C172M Starter Won't Engage

I had a similar problem. The problem was the bendix not "throwing out". I had it replaced. You don't have to change the whole starter.  As far as hand proping. Be sure that when you hand prop, that you are positioned so that you "fall" away from the prop. It does help to have someone in the cockpit with the brakes on.

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Re: C172M Starter Won't Engage

Every standard starter comes with a sticker on the side of the bendix which states "lubricate with silicone spray every 25hrs"

Why silicone? Silicone lubricants are "dry" lubricants which means they don't collect dust and dirt as readily as oil,grease, and say...hydraulic fluid.
I still encounter people who insist on wiping their struts down with 5606. Ever touch that black sticky goo on the bottom of the strut shaft? That's 5606 after it's been exposed to the outside world.   How much dirt is *that* collecting??
Doing the silicone shoeshine on the strut once a week will save you many strut seal replacements....

Anywho...Back to your starter.
You've got a sticking bendix.  If you're lucky, and you carry a long flat head screw driver, you can manually engage the bendix into the propeller ring gear by pushing, tooth by tooth, on the bendix gear opposite the normal rotation.  If you're unlucky, you'll need to take the cowl off.

Just a word of caution here.  If the starter doesn't have the oomph to get the bendix out, there's a *slight* chance the engine won't send the bendix gear back into the housing.
This will present itself as a lovely grinding/whirring noise.  If the noise doesn't go away by say...700RPM, shut down and get another starter.  Treat yourself right and get a B&C or SkyTec starter as they don't use the same method of engaging the pinion gear.

Once you're back home and have a spare moment, go get some silicone spray and let loose on the bendix.  There's a drain on the underside of the bendix housing.  When the drainage turns clear...you're done <grin>.

As for hand propping, GET SOME INSTRUCTION on doing this procedure correctly.  I've always been concerned that many pilot's are not trained to hand prop (but then again most pilots aren't taught to recover from spins *either* <sigh>)

Also, many of the single engine Cessna's do not have the propeller indexed in a good position for hand propping. 

If the impulse coupling "clicks" at the 5 O-clock/11 O-clock position as you're looking at the front of the aircraft, you'll be bent over ala "guillotione" position to get the engine to start. 

If your prop is improperly indexed, you're not in that big a hurry now..get another starter and don't force someone to make one of the toughest telephone calls of their life.  I've made that call before.  I don't ever want to do it again.

Best regards,
RH

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Re: C172M Starter Won't Engage

RE hand propping....as Roger said...get some instruction.  You definately don't want to try that and have something go "slightly" wrong....there is no slightly wrong.  I almost got to see a guy get chased by his little taildragger...I just missed it.  The prop didn't get him, but his throttle was set a bit high.  When it fired up, the tiedown on the tail gave way...he dove out of the way and his pland gobbled up three other aircraft!
Many years ago, I learned that a prop CAN start if you move it just a couple of degrees...I went to straighten the prop to horizontal, so it would "look nice"....like all the other planes nearby.  The slight movement started the engine! The P-lead did come loose.  Fortunaltely the plane was tied down, there was very little gas in the carb AND I was taught to believe that the prop is ALWAYS "HOT". I had also been trained as a student how to hand prop a plane.
Always make sure you are not in the arc of the prop and cant fall into the arc if something goes wrong...
Find someone, perhaps an instructor, or at least a Cub or Champ pilot, to walk you through the procedures.
Blue skies
Michael

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Re: C172M Starter Won't Engage

Thanks for all great information and for being timely.  At least I'm not completely ingnorant about the starter now. 

Roger, I wasn't aware of the silicone until this past annual, and immediately forgot it until you just reminded me.  That's about 40 hours ago, the last time silicone was used.  I'll ask about the bendix gear, but I am at their mercy. 

The gentlemen I spoke to Friday night from Beach Aircraft Maintenance, seemed like a "good guy", had already talked about first confirming whether it was the startere and said could overnight a new one Monday, and have it ready by Tuesday. 

If it is the Bendix gear, would it be wise to just replace it or the entire starter, considering the cost of labor versus getting a new starter?  He mentioned something about a Kelley(sp?) starter.  If it comes down to it, I'll inquire about a B&C or SkyTec starter, as Roger suggested.  I'll be hitting the Web regarding cost.

I was only half kidding about the hand propping thing, but I'll start making inquiries into getting some training.  I would be nice to at least have an option when landing at a field without maintenance facilities..  might be able to get out of a jam like this.

thanks again!

.

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Re: C172M Starter Won't Engage

Michael,

I forgot to mention, in my neighborhood we keep the prop vertical.  Less area for our feathered friends to perch!

Some people put these ugly owls on the top, the birds seem to laugh at them. Some use rubber snakes, whirling metal wind chimes, and intermittent eagle screaches.  I'm not sure anything will work.  Maybe we can hire someone to chase them away?

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Re: C172M Starter Won't Engage

Turns out the starter is shot.  I'm going to install a B&C starter.  This requires a minor change to the installation support.  It's slightly more expensive than a new starter of the same kind I have.  I will try to sell the core of the starter coming out. 

I contacted Aircraft Spruce and they connected me with B&C to both answer my questions and the representative called the maintence shop to explain the required change to the support.  They seem very customer service oriented, which was a plus to me for making the sale.  From what I could find out, it seems the B&C is a quality part.  Although I could have gotten an overhualed starter of the same type I have now for about $300 less, the cost of getting stuck somewhere because of an early failure far exceeds the additional cost.

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Re: C172M Starter Won't Engage

I have a C172N and ran into the same problem.  I now lubricate the bendix with silicone spray at each oil change and any time I have the cowl off.  It's not even a real chore to do it while the cowl is still on.  Problem solved, at least in my case.

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Re: C172M Starter Won't Engage

Barney:  What kind of spray do you use and where can I get it?

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Re: C172M Starter Won't Engage

<Turns out the starter is shot. I'm going to install a B&C starter. This requires a minor change to the installation support.>

Did I say "a minor change to the installation support"?  Well, that was true for the part connected to the Engine.  I guess the STC was only good for mounting the starter on the engine.  (Being a relatively new owner, I wasn't aware of this subtlety -- or not so subtle!)

Oh, I guess the manufacturer forgot to mention (or unaware) that there are a few other changes needed to put the cowling back on  inlcuding moving the hose connection for cabint heat in the baffle?  After all, a C172 is not such a common plane, yeh right!

8+ manhours later the starter was installed. I guess I was lucky that the shop gave me a break on the labor.  The manufacturer probably knew, that if I had the whole story I wouldn't have bought his product.  The SkyTec looked a little more like the original starter form, but I, unforturnately didn't expect the difficulties so I didn't make a study of it.  Please don't take it that I am endorsing the SkyTect, I don't know any more about it that would lead me to believe it would fit better.   The A&P  said he has been removing the Magna Flite Starter on many aircraft as they don't do well in hot weather.  He was impressed, though, by the B&C.

Hope this post helps someone else when thinking of making similar changes.

On the plus side, the starter is a quality part, spins the prop much faster than the original, and draws less cold cranking current.   

However, according to the manufacturer, on a carbureted engine the cranking the engine faster is not much of an advantage like it is for a fuel injected engine.  I can see his point as the fueling aspect would not be affected much, but my experience with push starting cars is that the the faster they go when you "Pop the clutch" the more likely it is to start.  I'm not sure how much a faster spinning prop helps a fowled plug or one with condensation on it shorting out the spark.  The lower current draw and no ongoing maintenance requirment is definitely a plus!  The downside is, now I will have to continue using that product because of the custom fit! Going back would be painful. 

I'm also a little concerned about one of the modifications.  With the new starter installed, one side of a vertical metal support had its bolt removed.  The support I'm talking about attaches to airbox inlet near the filter element and has nothing to do with the starter.  It looks a bit weaker and can vibrate more - not good, but judged by the Shop to be acceptable.

I'm also have one more bracket that supports the bumper under the landing light that needs to be welded and installed.  The shop said to do it, but it is not necessary for airworthiness. So still more to do.

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Re: C172M Starter Won't Engage

(Don't you wish you could just edit your previous posts?)

I wanted to add, one of the benefits of the B&C starter is produces higher starting torque via a geared arrangement.

On cold days, I will still manually turn the prop prior to starting.

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Re: C172M Starter Won't Engage

I have that same style starter and I am wondering if it starts the engine the same? What I mean is my engine seems to start "after" I let go of the key. I was told that the starter may be turning the prop "too" fast and therefore the speed is in excess of the impulse coupling RPMs range and when it winds down the impulse kicks in, thus starting the engine.

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Re: C172M Starter Won't Engage

I think you'll find the investment into the B&C starter worthwhile.

Don, from what you describe, you may have your P-leads switched or simply a bad ignition switch.

The impulse couplings should be engaged up to about 450RPM.
The B&C starter may be good, but it's not *that* good <grin>

In *some* applications, the RH magneto does not have an impulse coupling. 
To prevent kickback, the RH magneto is shut off when the key is turned to the "Start" position.

In any event, the check is simple, but requires removing the P-leads from the mags.  This in effect, turns the mags on. 
So disconnect the sparkplug leads from each spark plug before disconnecting the P-leads.

Once the P-leads are disconnected, you can use an ohmmeter to check for continuity to ground on the P-leads. 
With the switch in the "R" position, the LH P-lead should be grounded.
With the switch in the "L" position, the RH P-lead should be grounded
With the switch in the "Both" position, neither P-lead should be grounded.

While you're checking the wires, tug, push, and jiggle the key in each and all positions to see if any changes occur.
If something changes by jiggling the key without moving out of the position detent, have the switch checked.

Best regards,
RH

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Re: C172M Starter Won't Engage

Thanks for the info. I did have that done and I also had the shorting wire checked to "turn off" one mag. to prevent kickback. I had my a/p look at all of those situations and thay all check good. I went down that path as the manufacterer told me to. But still I have the same situation. I would not call it a problem because it "does" start.

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Re: C172M Starter Won't Engage

Don,

I always keep the starter engaged until the engine starts.  So I have never noticed what you have described.  But you see how much both of us learned just asking the question.  Thanks to Roger!

Roger,

Thanks for your suggestions.  Although the starter cost a lot, I will see if it pays off tomorrow.  It's going to be cold outside and I'll be starting the plane early.  I'll let you know how it turns out....

Barry

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Re: C172M Starter Won't Engage

Don,
Just so I can get this clear in my mind....<grin>

If you twist to start, the engine will "whirr whirr whirr" until the battery goes dead or you release from the "start" position (at which point the engine starts)?

If this is the case, I'd bet a dozen doughnuts on the ignition switch.


Cheers,
RH

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Re: C172M Starter Won't Engage

Don,

On this cold morning in Delaware low 30's (OK cold for my plane), the engine started after two or three, extra fast, propellar, revolutions. (so fast I'm not sure whether it was two or three <grin>) I took the ignition switch out of start after the engine caught!

Barry

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Re: C172M Starter Won't Engage

i just bought a brand new re-biuld starter for my 1965 mustang, it seems to engage at the store because i had them test it, but when i put it in the car, it doesn't turn the flywheel  any suggestions

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Re: C172M Starter Won't Engage

Yes, It tries to start but never really gets going until I let it go.

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Re: C172M Starter Won't Engage

If I hear a loud distinct metallic "click" or "clunk" as the starter first engages, could this also mean that the bendix needs lube? 
Also, an unrelated question, what is your preferred cold-weather starting procedure?
Thanks,
Steve

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Re: C172M Starter Won't Engage

RE: the Bendix.

I heard the motor on the starter spin fast, high pitch whining (no comments please!), but no clicking or clunking.  The clicking or clunking sounds like a battery problem.

RE: Cold weather starting procedure
(Assuming you have no engine heater.)

Before climbing inside, I "pull the prop through" a couple of times, i.e. move the propeller through a couple of full rotations.

prime 6 times
pump the throttle twice
(kiss my wife, if available)
then crank it up

If it just turns and no indication of catching, then I assume I flooded it.  So while its still turning, I use full throttle and pull the mixture to full cut-off. (This is to get rid of overage in fuel)
As soon as begins to catch I  move the mixture in and throttle back.  I don't like the engine to race with low lubrication.

I keep the RPMs 800 to 1000, while I let the engine heat up a bit.

If it doesn't start in three tries, waiting 5 to 10 minutes between tries.  I check the plugs for fouling and clean them if I can.  Especially the 4 lower plugs.  Having good clean plugs really helps!

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Re: C172M Starter Won't Engage

barry,
replace the bendix (i did two this week)
brad

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Re: C172M Starter Won't Engage

i have a 1975 cessna 150m. the starter seems to drag and makes noise .  it will engage after several attempts.  when cold is ok  seems when it has flown a while and is warm will is worse. what do i need to do?  tj

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