Bendix starter sporadically starts in cold weather

[mandm]

I recently posted about flying to Pilot Pete’s and after having dinner being unable to start the plane (in cold weather), luckily I was saved by two gentlemen who hand propped the airplane. The issue seemed to repeat itself sporadically, when turning the key to start the engine, the Bendix starter made a “whinning” noise and the prop was zero motion. I did some searching online and it seemed that one should check the teeth/gear by the prop flywheel for any buildup, one post said to apply WD40, but most posts opted for a silicone lubricant.

So yesterday, I pulled the airplane out of the hangar and the same issue occurred and I was unable to start the airplane. I thought about hand propping but realized I didn’t have the expertise needed so opted not to try that solo, and I placed the airplane back in the hangar.

Anyway, I placed a screwdriver into the starter gear to rotate the gear, and it clicked (almost like the gear was stuck in an engaged position but clearly the gear was not out towards the flywheel). At that point, I said I need to try it again and that my next option was to spray some WD40 on this to see what’s going on. Pulled the airplane out of the hangar and it started right up. The starter gear seemed to freely rotate so I do not think there was anything slowing or blocking it but perhaps the cold weather kept the gear from fully retracting therefore preventing the next start sequence. Although I am not sure, just sharing for some further thoughts.

 

[Bell206]

Although I am not sure, just sharing for some further thoughts.

FYI: you may want to have your AP determine why the starter gear is sticking in the ring gear. If there is a mechanical issue it could lead to that gear remaining engage once your engine starts which can cause more serious problems you don't want. For example, your current oil leak could be contaminating the starter/bendix assemblies, there is something loose in the bendix/starter installation, etc.

 

[MajorTurbulence]

It was common with my old Prestolite starter/Bendix gear on my Archer2. Recall discovering the screwdriver trick after a winter’s overnight stay enroute to New Orleans. Thereafter, I was always prepared for that possibility during the winter. Ultimately, changing to a SkyTec light weight starter eliminated that problem forever.

 

[unsafervguy]

very typical for starters that are not maintained and lubricated properly. what ever was sprayed on them them to lubricate them gets really gunky in cold weather and stops the bendix from engaging when energized. the motor spins but no prop rotation. the solution is to disassemble it, clean it and lubricate it properly at the proper intervals with the proper lubricant.

 

[Domenick]

First, do not use WD-40. It eventually turns to goo.
This is my guess based on my Piper Prestolite starter experience.

When the starter spins, centripetal force throws the starter's bendix drive gear into the ring gear. The engine turns and starts. When engine RPM exceeds starter RPM, centripetal force throws the bendix gear back out of ring gear engagement.(The bendix gear shaft has a very interesting double spiral cut into it).

One issue that often occurs is the starter's bendix gear (shaft) gets gummed up and despite the starter spinning, the bendix drive gear is stuck in place and does not engage the ring gear. You'll hear the starter whine and the engine will not turn over. This often occurs when the engine/starter is cold, but may not occur when the engine is warm. This is because the gunk warms up and loosens.

The opposite issue is the bendix drive gear will engage, the engine will start, but the bendix gear will not retract. In this case you'll hear a godawful racket. Shut down the engine IMMEDIATELY. Ring gears are expensive and a pain to replace.

A TEMPORARILY kludge for the first issue: Upon shutdown of the engine, bump the starter while the engine/starter is warm. This will throw the starter's bendix drive gear into the ring gear, so it is engaged for the next start.

Sometimes, flooding the appropriate area of the starter bendix with starter fluid or brake cleaner will soften up and flush enough goo to restore function. Don't knock yourself out with the vapors or apply to a warm engine. Might also want to pull the battery ground. Depending on the starter placement this attempted flush may be accomplished in place or the starter may need to be pulled.

Personally, I lived with my malfunction for a few days, then tried the in-place flush which worked for awhile. In the end, I pulled the starter and rather than muck about trying to clean the bendix drive, they were inexpensive enough at Aircraft Spruce, that I simply replaced the bendix drive unit.

 

[Dan Thomas]

When all else fails, read the instructions. If you want reliable operation, read the instructions BEFORE all else fails.

From https://www.lycoming.com/content/how-clean-your-direct-drive-engine-starter




People who use oil of any sort on that drive are just making things a lot worse. If one starts with the silicone, and stays with it, they'll have no trouble. I made a long tube out of two tubes (that come with the dry silicone lube spray can) and using a bit of heat from a lighter, softened one end and bent it into a short 90° angle. That was to get the spray way into the back behind the starter drive and onto the splines. Bump the starter to get it engaged with the flywheel (it will lock there) and get the spray into where it needs to go. Turn the prop backwards a tiny bit to rotate the starter and get more splines.

The drive will unlock once the engine starts.

 

[mandm]

When all else fails, read the instructions. If you want reliable operation, read the instructions BEFORE all else fails.

From https://www.lycoming.com/content/how-clean-your-direct-drive-engine-starter

View attachment 105463
View attachment 105464

People who use oil of any sort on that drive are just making things a lot worse. If one starts with the silicone, and stays with it, they'll have no trouble. I made a long tube out of two tubes (that come with the dry silicone lube spray can) and using a bit of heat from a lighter, softened one end and bent it into a short 90° angle. That was to get the spray way into the back behind the starter drive and onto the splines. Bump the starter to get it engaged with the flywheel (it will lock there) and get the spray into where it needs to go. Turn the prop backwards a tiny bit to rotate the starter and get more splines.

The drive will unlock once the engine starts.

If you push the starter gear will it retract outward to meet the flywheel? And turn the prop?

I also saw there is WD40 Silicone version, any thoughts on that?

My starter is 25 years old, will be sending it out for overhaul. Price incl install is just under $500.

 

[Dan Thomas]

If you push the starter gear will it retract outward to meet the flywheel? And turn the prop?

I also saw there is WD40 Silicone version, any thoughts on that?

My starter is 25 years old, will be sending it out for overhaul. Price incl install is just under $500.

"Bumping" the starter means turning the ignition key just briefly, to get the starter engaged. That particular starter drive has an internal, centrifugally-actuated lock that hold the gear engaged until the engine starts and will spin the gear up enough to unlock it, and it will retract.

Those old starters are often not worth overhauling. You might be better off installing an STC'd starter like the SkyTec. It doesn't use that inertial Bendix; it has a solenoid that engages and disengages the gear. And it weighs less. And it uses less current.

https://skytec.aero/product/lycoming-aircraft-starters/

I installed several of the NL starters. They worked well. Beware: There are a couple of different gear pitches, and you need to know what ring gear is on your engine. Count the teeth.

The WD-40 silicone is the stuff.

 

[Magman]

I agree with Dan’s comment on new type Starter superiority .

One caveat though.

The faster an engine with impulse coupled mags spins the more the “Effective Starting Timing “ ( my term) will be retarded. This can cause starting issues with some engines; particularly those with old mags.

The O-235- L2C ( Cessna 152) is the poster child for this. A change in magneto lag angle and a slow speed Starter cured the condition.

 

[Jdm]

You might be better off installing an STC'd starter like the SkyTec.

I thought they were STC’d but the sky-tec website shows them being FAA/PMA’d for most every engine mow. Are they still sending out STC paperwork?

One caveat though.
The faster an engine with impulse coupled mags spins the more the “Effective Starting Timing “ ( my term) will be retarded. This can cause starting issues with some engines; particularly those with old mags.

Any concerns in regards to this on an O-320 with slicks? I read someplace that it’d have to spin 400RPM to adversely affect it. No idea if that’s correct, just something I stumbled across.

 

[Dan Thomas]

Any concerns in regards to this on an O-320 with slicks? I read someplace that it’d have to spin 400RPM to adversely affect it. No idea if that’s correct, just something I stumbled across.

We ran the SkyTecs on O-320s with Slicks and never had any problems.

 

[Gary Ward]

If you push the starter gear will it retract outward to meet the flywheel? And turn the prop?

I also saw there is WD40 Silicone version, any thoughts on that?

My starter is 25 years old, will be sending it out for overhaul. Price incl install is just under $500.

For 500 for a overhaul, I think you should consider the Sky Tech starter.

My AP mechanic predicted that my 40 year old one would give up about 9 months before it died. He suggested the Sky Tech so that is what I got,NL

Mine has been great, no trouble at all so far. I just looked at my logs I have 477 engine hours on it. I installed it 11-8-19. Not much of the 477 hours were XC, mostly short trips and lots of start’s. Been on 2 different engines in my plane so far.

 

[5MikeCharlie]

Is your battery in good condition and fully charged? You symptoms could be caused by a weak battery.

 

[Dan Thomas]

Is your battery in good condition and fully charged? You symptoms could be caused by a weak battery.

Read the OP's post again. He pulled the starter gear into engagement with the flywheel gear, and it started right up. No weak battery.

These starter bendixes are far more often troublesome than weak batteries. They get dust and dirt blown into them. People oil them, making the problem far worse. They were used on cars for decades, but in the car they're inside the bellhousing and protected from the worst of the dirt. Still, they were problematic and carmakers went to solenoid-engagement starters a long time ago, which the SkyTec and others are. There is a time to abandon stupid stuff.

 

[Gary Ward]

I fly about 250 hrs a year, can you imagine taking off the starter 5 times a year to clean and lube it?