How we fixed my mate's Starter Motor. (Not how you’d think!)

[SimonRHC]

See Fig 3 on this webpage below

 

http://www.procarcare.com/icarumba/resourcecenter/encyclopedia/icar_resourcecenter_encyclopedia_starting1.asp

 

This is a link to some diagrams of a slightly different starter motor.

I have included it to help with my explanation even though the design is slightly different.

 

Whilst fixing a mate's K-Series starter motor the other week i discovered a problem with the manufacture of the starter.

 

He had wrapped his exhaust to try and reduce the under bonnet temp etc but to no luck.

 

He was now experiencing "click no start's" whilst hot OR cold.

 

Having spent the last 8 years designing starter motors i offered to have a look at it before he spent lots of money on an (unnecessary) special “starter” motor.

 

I slowly and methodically stripped part of the starter. (The whole process took no more then 30 mins.)

 

I removed the "Motor Strap" (the stiff wire that runs from the solenoid negative terminal to the motor body.

(See the wire coming out of the top of part 14 in Fig 3 of the above address)

 

I then undid the 2 bolts that held the solenoid to the starter casting.

(Listed as part 6 on Fig 3)

 

I then gently removed the solenoid body.

(Part 2)

 

The solenoid plunger stays loosely attached to the starter casting because the plunger’s end is attached to a lever inside the casting.

(Part 8)

 

The first thing i noticed whilst looking at the plunger is that it was worn at the top-front and bottom-back.

 

This indicated to me that the centre axis of the plunger was not in line with the centre axis of the solenoid during operation.

 

Something was creating a side load on the plunger that was causing it to bind up during operation.

This would account for a non-temperature related “click no start”.

 

The pull force of a solenoid at the early stages of the plunger travel is very weak and if the plunger gets stuck the coil heats up rapidly making the pull force even weaker in a catch 22 type situation.

 

When a solenoid plunger has been worn diagonally due to a side load i always look at the interface between the plunger and the lever.

 

The end of a lever moves in a circular path (an arc) where as the plunger needs to move in a straight line.

 

It is therefore imperative that the end of the lever slides smoothly against the end of the plunger so that they can move in their (slightly different paths).

 

The end of the plunger has a kind of mushroom shaped end that sits over a fork shape end on the lever.

 

The lever is a pressing, stamped out of a sheet like a ginger bread man shape being cut out.

When this is done the upper cut edge has a rounded profile (fillet) because the metal is being bent slightly.

The lower edge has a very sharp corner because it is being sheared.

 

Looking closely at the lower edge it still had this sharp edge present and has not been de-burred adequately.

 

This sharp edge (around the knuckle of the levers fork) is digging into the mushroom end of the plunger.

As the end of the lever moves in an arc it is bound up with the end of the plunger. This causes the end of the plunger to try and move in an arc creating a side load on the plunger and causing it to bind up, hence click no start.

 

With a small file I removed the sharp edges on the lever so that they couldn’t snag.

I noticed that the grease inside the casting had become thick and blackened with brush dust so I cleaned it out.

 

I lightly greased the fork of the leaver, the mushroom end on the plunger and (very lightly greased) the plunger outside diameter.

 

The areas were greased during manufacture but because the starter is mounted up side down (the solenoid at the bottom) the brush dust collects around the plunger drying up the grease.

 

It is not ideal to have the solenoid as the lowest point on the starter.

Although there is a drain tube to let the water out the brush dust will still sit there mixing with the grease.

 

If the solenoid is at the top the brush dust ends up sat inside the starter frame (part 13) where it does little damage.

 

Because the starter is mounted up-side down it may be necessary to clean and re-grease the plunger and lever every now and then.

 

Be very careful when tightening the nuts not to over torque then because many of them bolt through “Bakelite” which can shatter.

 

I hope this helps you fix your starter.

Being an engineer I am aware that this simplified explanation may make no sense to a lot of people.

If I have confused you please post back and I’ll try and clear it up.

Don’t invalidate your warranty, but if you are out of warranty, it’s a very easy job that only requires new grease.

 

Cheers

Simon

 

[Dannyboy]

Thanks Si!! I'll be round in 6months with mine in bits for you 😬 😬 😬

 

Must have a chat sometime....Change in circumstances means I'm closer by than I have been for a long while!

 

Dannyboy

 

[dreamer_uk75]

Taking mine apart, cleaning it up, and re-greasing the solenoid seems to have worked for mine too :)

 

:thumbup:

[Tony Whitley]

Oooh! A new theory It sounds feasible, I'll give it a try if mine fails.

 

dreamer: been there, got the T shirt. It doesn't last - I did mine so often I could remove, strip down, and refit it in less than 15 minutes before I gave up and bought a new one.

 

My theory is that soldering a wire to the solenoid and taking that via a relay direct to the battery to ensure maximum volts at the solenoid has meant 3 years / 20k miles trouble-free for me

[david nelson]

Yes its still working. Used the 7 for a month every day and no problems.

Its useful to have friends who know about started motors. Saved me loads of money. Thanks Si *thumbup*

 

 

David

[Unclefester]

I've saved this one for future reference!

 

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

[shn7]

Great clear explanation. Having stripped my solenoid apart and cleaned/regreased in the past it makes perfect sense to me. If I take mine apart again I'll certainly look more closely at the plunger and lever.

 

Steve.

Sussex (West) AO

Not forgetting Percy the Polar Bear

[RobW]

Crossflow starters are so cheap if you ever have a problem it's easier to just fit a new one !

[susser]

This is brilliant.

This is a case of solving the problem. I believe that if you ask the question "what's the problem" enough times, you'll find out.

If your answer to the question "What's the problem ?" is "The starter won't work", then you're not a problem solver.

I'm called "susser" at work because of my methodical problem solving skills.

well done that Naked Engineer.

[dreamer_uk75]

Tony - bugger, thought I had it cracked :( I've also wrapped it in heat shield to help protect it...