Random starter motor sticking

[Rockape]

Have started and stopped the engine many times. 
 

went for a run in the Sun today. Stopped for coffee - started the car - clunk….just the relay closing.

 

put the car in gear and with a bit of help got it to move and you could here the starter motor dis-engage. Turned the key and everything fine.

 

so - why did the starter motor stick on? Is there a service one can do to find/eliminate this? 
 

mark

[NonMember]

Is that a Bendix or a pre-engaged? The mechanism is different but both can do something like that. My GT6 has, on two or three occasions over the last 30 years, refused to start with just a clunk, and then wouldn't roll in gear (in fact one time it locked the rear wheels when I tried to bump start it). And then the Bendix frees off the ring gear and everything's happy again.

I don't fully understand how it happens but cleaning the Bendix and letting it dry (DO NOT LUBRICATE with oil or grease; they'll just turn into glue with the clutch powder in the housing) should keep it happy for a while.

[Pete Lewis]

and to add check all main lead connections for corrosion a low current can fail to spin over and the starter motor stalls as soon as it hits the flywheel 

to clean the bendix  a wash in petrol works well   

and as Rob says no oiling keep it dry 

Pete

 

[Rockape]

Thanks ….need to read and remind myself what a Bendix is…🤔

but here’s what happens when I come to start the car.

after a long lay off, it just cranks.

but then eventually it cranks, and then followed by a whirring noise. This is a clue that it’s about to fire - ( I assume would be due to a little bit of power from an ignition, and the Bendix disengaging - does that make any kind of sense?)

Cleaning - I assume remove starter motor - inspect, clean and re-install - which shouldn’t be too big a job - LOL !

 

 

[Rockape]

6 hours ago, NonMember said:

Is that a Bendix or a pre-engaged? The mechanism is different but both can do something like that. My GT6 has, on two or three occasions over the last 30 years, refused to start with just a clunk, and then wouldn't roll in gear (in fact one time it locked the rear wheels when I tried to bump start it). And then the Bendix frees off the ring gear and everything's happy again.

I don't fully understand how it happens but cleaning the Bendix and letting it dry (DO NOT LUBRICATE with oil or grease; they'll just turn into glue with the clutch powder in the housing) should keep it happy for a while.

That is pretty much what happened today. I couldn’t move the engine with it in gear (thought for a minute I had somehow seized the engine)  But three of us (with the car in 3rd) managed to free it off.

[PeteH]

"Rocking" the car often free`s them up. As will a Gentle tap on the S-M with a Device, hammer, start handle, whatever. Spanner on the square of the spindle will often work too.

As previous stated clean, don`t lubricate, and check/confirm battery health.

Pete

[NonMember]

9 hours ago, Rockape said:

but then eventually it cranks, and then followed by a whirring noise. This is a clue that it’s about to fire

Whirring noise and no action? Then when you try again it usually fires? If so, that's classic "premature disengagement", usually caused by the carbs having been dry, so you've done all that cranking to get almost enough fuel in to fire but it only fires once - enough to kick the starter Bendix out but not enough to keep the engine running. My Toledo used to do it regularly.

[Unkel Kunkel]

The Bendix is a such a neat  design:

The pinion is attached to the starter shaft by a “quick thread”.

When the starter motor is turned on, the shaft begins to quickly rotate.The pinion gear has inertia - there is sufficient mass for it to resist this initial spinning  so instead to spinning with the shaft, it winds its way down the thread and meshes with the flywheel:

If the engine starts, the ring gear speed exceeds the pinion so it gets flung out of engagement, down the thread and against the buffer spring.

It so rarely gives trouble.

The pinion can stick meshed to the ring gear.

= Put the car in top gear with the ignition off.

then rock the car backwards and forwards - this doesn’t need a great deal if effort and can be done quite gently and easily by one person.It should free easily or at most  a very few rocks should free with a click and more free movement.

 

Usually, the  cause is the Bendix gear is gummed up with dirt and crud and a bit of oil from inside the bell housing.

cleaning and degreasing and leaving it  un-lubricated sorts most.

Sometimes the pinion gear is chewed up and ocassionally the ring gear.

A new Bendix gear can fitted (though the buffer spring is a bit fiddly unless you have the special compressor)

Have a look at the brushes- if they are worn and the starter pinion  is a bit chewed, maybe time to completely overhaul the starter  - or go for new one.

[DerekS]

Morning all! An old trick is after cleaning the bendix, give the sliding surfaces a going over with the "lead" of a pencil. Get as much of the graphite on as you can. It's very effective and lasts a surprisingly long time. 

While I'm here, when I try to reply to posts on my Samsung phone, all of a sudden the page jumps and if I'm not careful I submit a column 3 feet in length... Why?

Derek.

[Rockape]

Thanks for all the tips - and the detailed description of the Bendix system. 
 

just off to get me spanners….

any tips on SM removal O need to know?

is it -

disconnect battery.

disconnect lead to SM

Undo the two (?) bolts

withdraw SM from ring gear

1 hour ago, NonMember said:

Whirring noise and no action? Then when you try again it usually fires? If so, that's classic "premature disengagement", usually caused by the carbs having been dry, so you've done all that cranking to get almost enough fuel in to fire but it only fires once - enough to kick the starter Bendix out but not enough to keep the engine running. My Toledo used to do it regularly.

 

35 minutes ago, Unkel Kunkel said:

The Bendix is a such a neat  design:

The pinion is attached to the starter shaft by a “quick thread”.

When the starter motor is turned on, the shaft begins to quickly rotate.The pinion gear has inertia - there is sufficient mass for it to resist this initial spinning  so instead to spinning with the shaft, it winds its way down the thread and meshes with the flywheel:

If the engine starts, the ring gear speed exceeds the pinion so it gets flung out of engagement, down the thread and against the buffer spring.

It so rarely gives trouble.

The pinion can stick meshed to the ring gear.

= Put the car in top gear with the ignition off.

then rock the car backwards and forwards - this doesn’t need a great deal if effort and can be done quite gently and easily by one person.It should free easily or at most  a very few rocks should free with a click and more free movement.

 

Usually, the  cause is the Bendix gear is gummed up with dirt and crud and a bit of oil from inside the bell housing.

cleaning and degreasing and leaving it  un-lubricated sorts most.

Sometimes the pinion gear is chewed up and ocassionally the ring gear.

A new Bendix gear can fitted (though the buffer spring is a bit fiddly unless you have the special compressor)

Have a look at the brushes- if they are worn and the starter pinion  is a bit chewed, maybe time to completely overhaul the starter  - or go for new one.

Cheerd

 

[NonMember]

22 minutes ago, Rockape said:

any tips on SM removal

Pretty much as your list. How easy it is depends on what car - your profile says Mk3 Spitfire so access is fairly easy (although the engine bay valances get in the way a bit). Note the spacer and shims (not always the same number so see what you have and keep them in order). Take care when undoing (or refitting) the cable, as it's possible to turn the post instead of undoing the nut, and turning it too far will break the internal wiring.

[Pete Lewis]

1 hour ago, derekskill said:

submit a column 3 feet in length

you mean youre talking at great lengths    Ha ! 

tech is wonderful thing if it works things have just become far too complicated for simple tasks 

my back up laptop on win 11 you only have to blink and the darn thing selects stuff from all over the  place thats not wanted   

Pete

[dougbgt6]

2 hours ago, NonMember said:

that's classic "premature disengagement"

Yeh, my ex used to complain about that.

As said clean with petrol, no oil or grease. I have it in the back of my mind someone recommended graphite, but that might be a figment of my imagination. I've used it on plastic curtain rails, works well.

Doug

[Pete Lewis]

you got curtains in the |GT6 ?????????  flash git  

Pete

[dougbgt6]

Yeh, you need a bit of privacy, on occasion.

Doug

[johny]

I know its exciting driving a Triumph but even so😲

[PeteH]

I've used it on plastic curtain rails, works well.
 

“Mr Sheen” also works well on plastic rail. Not so good on Start Motors though I suspect

Pete