Jump to content

4K Corolla Starter Motor Problem


Recommended Posts

My 1974 (48 yo) KE30 2 door Rolla has a tow bar, & often gets asked to tow a load of green waste to the local dump.  This weekend was such an occasion, & after dropping off the second load, I started the car up, as normal; without issues, & slowly drove out of the dump.  As I drove up a slight rise towards the entrance gates, I heard a scratching/grating noise, emanating from under the car. I assumed I had picked some scrap up under the car, that was caught; & was grating on the asphalt.  As soon as I exited the dump, I pulled onto the side of the road, left the engine running & quickly looked under the car. Nothing at all !  I then lifted the bonnet, & the engine was still running, but making some strange noises, from what I thought; was it's "inner workings".  What could it be ?  I have had 4K motors, that with failed timing chain tensioners, or with low oil pressure at idle; resulting in a "stretched" timing chain "slapping" against the inner side of the timing chain cover. However, my 4K-U has a dual chain, so it wasn't that. As I was only 3klms from home, & the trailer was now empty, I decided to head for home slowly, & investigate, once I was in arms reach of a selection of tools.

Within 1/2 a klm, the engine started to deteriorate in performance, & a quick look at the voltage reading, on a dash guage; indicted that the battery was  about 8-11V, & fluctuating.

Eventually, I knew it wasn't going to make it home, so pulled over, turned the engine off, & again lifted the bonnet. Nothing was obvious, so I tried to restart the car.  Dead with the battery voltage around 7-8 volt.  So a quick call to my wife, She arrives with her 2009 Corolla, & I tow the KE30 + trailer home, as a trio, with firm instructions that She will have to push the brake pedal harder, as there is now no vacuum assistance.

My head is now taking in all I have observed in the last hour, & trying to determine what could it be ?

I have read & heard of a situation, where a starter motor pinion; will not disengaged after the car starts, & the engine then drives the starter motor at rotational speeds, it was never designed for.  Although I had read about this particular scenario, I had never ever experienced it, in all my years with playing, & working with Rollas.

As any other possibility, involved internal engine investigation, I decided to remove the starter, as it is an external component, & relatively easy to remove, although not without some fiddling.  

With starter motor removed, & looking quite normal; with the pinion retracted, I decided to put it in in the bench vice, & power it up, & see if it worked.  Here is a good schematic, from the K Series "Yellow Bible".


Only difference, with my KE30, is that there is a "starting relay", between the ignition switch, & terminal 50, to prevent the ignition barrel having to handle the high current of the pull -in solenoid.  Notice, once the pull-in coil does it's job, & closes the "main contacts" to power the starter motor; those main contacts also s/c the pull-in coil, & the hold-in coil is only left with it's lower current requirement

With a 12V battery on the bench, I connected same to the starter motor with some heavy electrical wiring, as you would use with 10-15A power points. I turned to pick up a piece of wire to temporarily active the solenoid, but as I did so, I could smell something, & saw the connecting wires I had just connected, starting to melt their insultation. Grabbed a side cutters, & cut one of the wires.  The plot had just thickened, but at least my first guess of the starter motor, being the culprit, looked like it was a reasonable one.

To my knowledge, there are basically two types of starter motor arrangement, where the starter motor is a direct drive onto the flywheel ring gear.  One type has a scroll on the starter output shaft, so as it initially spins, it "throws the pinion towards the flywheel ring gear", which engages & turns & "cranks" the engine.

The second type, which is used in our Corollas, is a solenoid, on top of the starter motor, which via a lever movement, engages the pinion gear with the ring gears on the flywheel. Just as the engagement takes place a large switch on the solenoid, is closed & feeds 12 volts to the starter motor proper.  This system is preferred as the lightly spring loaded pinion, will always be engaged before the starter begins rotating.

I then remove the starter motor solenoid, & it looks & feels OK. As it needs a big soldering iron, to fully dissemble it, I put it aside, & remove the cap from the end of the now upturned starter in the bench vice.  As the cover came off, my eyes were met with devastation like I have never seen before.  The internals of the starter motor, had been pulverized, by the starter motor never disengaging from the flywheel ring gear; & being driven at speeds it was never designed for.


I suspect, that the contacts at the end of the solenoid, that switch power to the starter, have welded, & not released when the engine started.  I'll find out later this afternoon, when I get home, & unsolder the solenoid, & inspect.  There are a couple of other suspects like the ignition barrel, where the spring that returns the key switch from "Start", to "Run", has broken. There is also a "start relay', energized by the ignition barrel key start position, that switches power to the starter motor solenoid. However after removing, the starter motor, & finding the above pictured; a quick test with a test light on the output of the starter solenoid relay, indicated these items are both working perfectly.

So my question is;  is this a problem others have suffered, or heard of, as I have certainly not ever heard of it on these pages in the nearly 20 years I've been enjoying the threads on this forum ?

Cheers Banjo



Edited by Banjo
adding copy
Link to comment
Share on other sites

Members dont see this ad

Dissembled the solenoid this afternoon; half expecting to see the contacts inside the solenoid, to be welded together; or at least showing indication of burning & sticking.

Imagine, my surprise, when the all the contacts involved it the solenoid, had no "welding" or indication of sticking.  The solenoid was very smooth in it's action.



I referred to a Gregory's KE Series manual, & it describes the Bosch starter motor as having a clutch built into the pinion arrangement, so that if the ignition key was held in the "start" position, after the engine had started, that the pinion could not drive the starter motor.  My starter is a Nippondenso, so I looked closely at it; & it also has the same type clutch arrangement.  I tested the clutch, & it was performing perfectly.  This sort of blew my theory out of the water, that the pinion was stuck, & driving the starter motor at revs it couldn't withstand, & destroyed itself.

I then got a big soft hammer, & drove the damaged armature out of the starter body.   With the armature, separated from the starter housing, it was very easy to see what had occurred. Basically the commutator, where the brushes press up against; had broken down, and all those chunks & bits of broken copper were what remained of the commutator.  It's such a mess, that it is hard to tell, how the commutator broke up. 


Suffice to say, I'm pretty sure there is nothing "external", that has caused this issue; so I'll go ahead, & fit a spare starter motor I have here.

Starter motors fitted to K series motors have a hard & unloved life.  Living there, just under the exhaust manifold, they are subjected to lots of heat, & can't readily be inspected, unless removed; which I previous advised, is a bit difficult.  

It would be a very wise move, if you ever have your manifolds off, to simply remove the starter, remove the cover & see what state the commutator & brushes are in. 

Cheers Banjo



Link to comment
Share on other sites

"by the starter motor never disengaging from the flywheel ring gear; & being driven at speeds it was never designed for. "

When you start revving race car engines a few thousand rpm higher than stock, the altys are doing astounding revs. All I've ever seen happen are wires breaking as the centrifugal force overcomes the glues they use to hold them onto the armature, I've never seen anything disintergrate like that!

The commutator segments are glued together like an orange, and I suppose the glue failed over the years and a segment popped out and jammed against the brush tunnel.  Certainly spectacular!

Link to comment
Share on other sites


The commutator segments are glued together like an orange, and I suppose the glue failed over the years and a segment popped out and jammed against the brush tunnel.  Certainly spectacular!

Hi Keith, I think you are spot on. That is the same conclusion I came to yesterday, after delving into it a bit more.  You will see from the pics below, once I "hammered"  the armature out of the casing, that the enclosed area of the armature appears fairly contained.



I'd agree, that probably a dislodged commutator segment, caused all that havoc.

I'll put another starter in this afternoon, & will hopefully have my Rolla down off ramps, by dusk !



Cheers Banjo 

Link to comment
Share on other sites

Posted (edited)

Well, all good now, & the Rolla is mobile again.

It was just a case of the commutator section of the starter "collapsing".  Nothing externally, caused this fault.  Just olde age !

I did pull the "spare starter" I had, apart, before installing it.  I cleaned up the commutator with some 2000 grit emery paper, & also greased & oiled it, in the appropriate places, & "shinnied up" all the electrical connection points.   A quick test with the starter in a bench vice, with a battery & a couple of pieces of appropriate thickness wire is always a good idea, as it removes the need to remove & reinstall it, a second time, if you put it in, & it still has issues.

Most people removed the exhaust piping under the exhaust manifold, to get access, to remove the starter.  This can be a pain, because the threads on pipe flange to manifold, usually need a few hours of WD40, before they will move without issues.  I decided to see if I could get it out, from under the car, without removing the exhaust piping.  It is possible, but is a tight squeeze.  The obstacle is the long cross tie rod on the steering.  I found if I removed the two (2) mounting bracket bolts on the passengers side, securing the steering pivot assembly; & pull it downwards, it creates that little more room, to allow the starter to come out or in.

Some have commented, that the operation of the starter is a little more involved, than what most people would believe it does.

The following extract from a Gregorys manual I have here, explains it well.


Even the solenoid operation is a bit more involved.  Reference to the starter schematic below, indicates that the solenoid has two parallel windings.


The "operate/pull-in winding" draws more current, & power, than the 'hold-in winding", as more "force" is required, to engage the pinion with the flywheel ring gear quickly.  Once the pinion is engaged, it requires a smaller amount of power to hold the solenoid in position (hold-in winding).

When the solenoid operates; at the end of it's travel, it closes the large contacts, that feed 12 volts to the starter motor windings.  However, these contacts closing, also short out the "operate/pull-in winding', so only the "hold-in winding" is left energized.

I believe in some very early Corollas, the starter solenoid, was directly powered through the ignition switch in the start position.  As this current is fairly high, & the ignition barrel switch is a distance from the starter; the addition of a start relay, close to the starter, makes a lot of sense, reducing considerably the current passing through the ignition "start" switch contacts. Ignition barrel switch replacement can be a horrible job, as they are designed specifically, to be very, very difficult to remove.

(hacksaw blade without handle, a very large blade screwdriver, & about 40 minutes of swearing, if I remember last time I had to swap a barrel out)

Cheers Banjo 




Edited by Banjo
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...