Starter motor keeps cranking

Swan55 · January 9, 2018

Hello. This is my first post.

I have failed to find a post with this exact problem, but would welcome a pointer in the right direction if one already exists.

I have a problem with the starter in my 1998 LS400 (150,000 miles).

The starter motor is sticking on – it just keeps on cranking. The only way I can stop it is by disconnecting the Battery. I’ll include a bit of background in case it’s relevant:-

We had a new Bosch heavy duty Battery and a reconditioned alternator about 2 years ago.

The car is used daily and normally starts first time. About 6 weeks ago it failed to start first time for 4 consecutive days. There were a number of failure symptoms, comprising of some / most of the following :-

- the nights had just got colder, and with one exception, this only happened first thing in the morning. All other startups during the same day were fine.

- Mostly on turning the ignition key there was just silence, not even a little click.

- Eventually the starter would groan a few times, like a really drained battery;

- Then it would suddenly crank properly, the familiar and normal fast crank, and start as though there was nothing wrong.

- I had tried bumping it a bit in gear in case that dislodged something, but cannot say that that was the reason it then started.

Our mechanic tested the Battery and alternator and said they were fine. Then the car started properly 3 times a day for the next month.

Then, a couple of weeks ago, I turned the ignition key, the car started immediately, but I could tell that something was wrong. I turned the ignition key off and the starter was still cranking (with the engine now off). I turned the ignition on again and the engine started as normal but the starter was still cranking.

I removed the ignition key and the engine stops but the starter still cranks.

The only way to stop the starter cranking is by disconnecting the Battery.

Now, if I reconnect the Battery, the starter starts cranking even though the ignition key is not in the barrel.

I have changed the starter relay in the fuse box, but it’s still the same (cranks straightaway when Battery reconnected).

The starter cranks when the Battery is reconnected even if the starter relay in the fuse box is removed (and the ignition key out); which has really confused me.

I am hoping that this is not a case of accessing the starter motor unit, and would welcome your advice on the matter.

Many thanks, and a belated happy new year to you all.

sorcerer · January 9, 2018

Welcome to the Lexus Owners Club Nigel

I don't have an LS400, I'm not a mechanic and I'm not an auto electrician, so hopefully someone more knowledgeable than I will be along soon. In the meantime, for what it's worth....

I think the problem was initially a faulty or dying starter solenoid. When you turn the key, a small current is applied to the starter solenoid, which then electromagnetically pulls in a heavy set of contacts to allow a large current to flow to the starter motor (when cranking a starter motor it's almost like putting a direct short circuit across the Battery and the motor will draw 300 Amps or more).

The coil of the solenoid may have gone faulty and was not pulling the contacts in strongly enough, or maybe there's a loose connection to it or something. Either way, with a minimum of 300A flowing there will have been a lot of arcing and now the solenoid contacts seem to have welded themselves closed, thereby allowing continuous current flow to the starter motor and why it's running all the time.

Some cars have a separate starter solenoid but it's more common now I think to see it integrated into the starter motor and I'm afraid that I have no idea which way it is in the LS400.

Hope you get it sorted quickly and cheaply, whatever it turns out to be.

Texas · January 9, 2018

+1 on checking out the starter solenoid as above, this is a heavy duty switch that is perminantly connected between the Battery and the starter motor. The solenoid is operated by a low current circuit ( ignition key switch or push button on dash) so you do not have to have a whacking great big switch inside the car. The fact that the starter continues to spin after the key is off indicates that the contacts inside the solenoid are still made, as above this can be due to the fact the contacts have arced and welded themselves together so it is no longer a switch more of a link! Should be a easy inexpensive ( did I really say inexpensive when referring to fixing a Lexus!!!) fix as years ago it was a common failure on cars and designers will/should allow for this part to be accessible and reparable

paul m.

Note: I might be right with my 'Inexpensive' comment as I just found this on that site beginning with an E, not saying this is the correct one for your car but I would get in touch with the seller/shop and explain your symptoms and go from there...

https://www.ebay.co.uk/itm/LEXUS-LS400-4-0-V8-UCF10-UCF20-STARTER-MOTOR-SOLENOID-REPAIR-KIT/251277305501?hash=item3a814b669d:m:mfxbIAKAgUkc35A4Ho6X1PQ

A phone number can be found under "Buisness Seller Information " at bottom of page and click on 'Complete Information '

Texas · January 9, 2018

'How to' posted on their website,

http://www.repairkitsuk.com/3.html

paul m.

Swan55 · January 10, 2018

Dear Sorcerer and Texas,

Many thanks for your consideration and advice.

After reading so many forum articles regarding the complexity (and corresponding cost) of getting the starter out, I was / am really hoping that there might be other potential solutions to try first; although the more I read the more resigned I've become that your hunch is correct.

As suggested, I've messaged the solenoid repair kit people and await their response.

Attempting to solve this by adopting a "simple things first" approach LED me to acquiring a new relay in the fuse box, but to no avail.

As stated, when I reconnect the Battery, there are small sparks at the Battery terminal, and then the starter cranks; so clearly the circuit is staying "live". Could this be anything to do with the ignition switch or something in that area ?

All advice much appreciated.

thanks,

Nigel

sorcerer · January 10, 2018

21 minutes ago, Swan55 said:

As stated, when I reconnect the battery, there are small sparks at the battery terminal, and then the starter cranks; so clearly the circuit is staying "live". Could this be anything to do with the ignition switch or something in that area ?.

I suppose it could be, but it's not very likely and I very much doubt it. The most likely scenario is that the starter solenoid contacts have welded together so that you now have, in effect, just one big wire directly from the Battery to the starter motor, which is why you get sparks and the motor runs when you connect that wire to the Battery.

If you do want to try looking for problems with the ignition switch, or if you want to prove beyond doubt that it's the solenoid, you really need a multimeter for proper testing. Quite a decent one can be had for about £25-£30 but even a cheapo one at about a tenner would do. Easiest thing is to check for continuity on that big wire that you connect to the Battery. Switch the multimeter to measure resistance or to its continuity buzzer if it has one, put one croc clip on the wire at the Battery end* and the other croc clip or probe on the starter motor +ve terminal and I'll bet a week's wages that either the buzzer will sound or the meter needle will swing all the way over to the right (or give a reading of either zero or close to zero if it's a digital readout).

The solenoid is just a big switch so if it was working properly you wouldn't have continuity but I think you'll find that you have.

* Sorry if this sounds condescending but I don't know your level of electrical knowledge so, just remember that you're only looking for continuity, not voltage, so don't connect the wire to the Battery when (if) you do this test.

Swan55 · January 10, 2018

Sorcerer,

many thanks.

This will be a good test should we get to the stage of taking the inlet manifold (etc.) off so that we can get to the actual starter unit (a stage which I suspect is fast approaching).

In the meantime I'm off to buy a new Battery charger as she will be pretty low now after having just sat there for a couple of weeks.

regards,

NIgel

sorcerer · January 10, 2018

You're very welcome Nigel, hope you get it sorted without too much hassle. Good luck!

Texas · January 10, 2018

I am not au fait with the exact location of the starter and therefore solenoid on your car but in years gone by one remedy for a 'sticky' starter motor solenoid was to tap it with a hammer to free up the internal slider to make the contacts energise the starter motor. But in your case I feel that when dismantled you will find the contacts and slider contact have if fact fused together to some degree, like I said if accessible then a slight tap may free up the contacts as they have been sticking on and off in the past But they well may be stuck proper this time!

fraid to say you gonna have to go in and get starter motor out ( somehow) but if not doing it yourself then you can show the mechanic trusted to do job the 'How To' details and supply the parts yourself, all the best with this fix and please report back afterwards...

just found this might help once out!!!

paul m.

Swan55 · January 11, 2018

Sorcerer and Texas,

I believe you're correct. It's time do some mechanical work.

This will take me some time to arrange, but I will post back in due course.

I also heard back from the repairit online shop who also feel that it's probably a stuck solenoid.

Although the repair kit is a reasonable enough cost (below £20 inc p&p), and from the video above it looks as though it's not too difficult to diy, it's a pity that the starter unit itself is so inaccessible and requires so much work to get at it.

many thanks,

Nigel

Swan55 · January 11, 2018

I mentioned earlier that I had replaced the starter relay in the fuse box.

Unfortunately it did not solve the problem.

I was curious as to what goes on inside a relay and took some photographs, which I include below just for information.

My apologies that they have uploaded at different sizes.

In photo no 6, you can see the 'inside' view and the arrow shows the gap between the 2 contacts. This shows that the contacts are not welded together (which I had really hoped they were as this would then have only necessitated a replacement relay which would have been such a simple fix).

Also in photo no 8, you can see that the thin copper wire passes over its own contact plate (one on both sides of the relay), and again looks somewhat 'thin' and a bit 'melted' (there must be better terms); so again I hoped that a replacement relay would do the job, but alas, no such luck.

sorcerer · January 11, 2018

A valiant effort Nigel but that relay was never going to be the problem - it's a small relay, drawing a small current that's used to switch the much heavier current at the solenoid. As I mentioned earlier, a starter motor draws a minimum of about 300 Amps so it's at the big, heavy contacts at the solenoid end where the arcing takes place and where they can eventually weld together.

Swan55 · January 11, 2018

Sorcerer,

Yes it was rather optimistic of me to hope that the solution was going to be this simple - but nothing ventured etc. and in any event we can now safely rule it out of my confusion.

What is really confusing me, which I accept is part of a great ignorance on my behalf, is that the starter motor is continuously cranking, and keeps on doing so (the actual cranking 'noise' is as normal - no bad or strange grinding noises etc.). In fact if I turn the ignition key on - then the engine starts as normal - it's just that the starter keeps on cranking and does not disengage. I would have thought that if the solenoid was stuck / welded together, then the starter would make no noise or just a click etc.

I'm now off to buy a Battery charger, so that we can then be sure that that is not somehow adding to my confusion.

kind regards,

Nigel

sorcerer · January 11, 2018

A car engine has to go through its operational cycle in order to start. To 'crank' an engine means to turn it by external means, such as a crank handle in the old days or a starter motor in modern cars. Once the engine fires up, whatever was used to crank it becomes redundant, so in the case of a starter motor, you release the key when the engine fires, thereby shutting off the power supply to the motor and it stops spinning.

A switch is just a device that, if you move it to the 'on' position or 'close' it, it will 'make' the circuit and when you move it to the 'off' position or 'open' it, it 'breaks' the circuit. When you turn the key through the IGN position and on to the START position a few things happen, but in the context of this thread you're basically just closing a (low power) switch that energises an electromagnetic switch (the solenoid) which then pulls in a big, beefy set of contacts (a high power switch) and allows high Battery current to flow to the starter motor and makes it spin.

When the engine fires and you let go of the key, that opens the low power switch and cuts off power to the solenoid, which in turn should open the high power switch and stop the flow of high Battery current to the starter motor so that it stops spinning. Because (we think) that the solenoid contacts have welded together, letting go of the key has no effect. The solenoid contacts can't open so Battery power is constantly being supplied to the starter motor and causing it to spin continuously, so the noise of the motor turning is what you're hearing.

Texas · January 11, 2018

+1, that is why the ignition switch is spring loaded at the "Start" position of the key turning action.this is so the starter motor is only energised when you hold the key against the spring tension and ( most people hopefully then) let it return to the "Ignition" posistion once the car is running!

Like I said it appears that this is a known problem ( aftermarket kit available indicates this as there must be a market for it!) and quite an easy and inexpensive ( there I said it again!) fix once the starter is on the bench.

I have watched a couple of YouToob vids of starter removals on the LS400 series and Even though I don't envy you it looks like a 'doable' job with no special tools required and done from above ( so no raising of vehicle required). it appears that the biggest problem is a pipe at the rear that hinders the fixing bolts to the motor/solenoid unit, but one Vid I watched done the solenoid contact change with the starter/solenoid still fixed to the engine by taking the solenoid cover off.

Paul m.

Sherra · January 11, 2018

Top quality photos Nigel

Texas · January 11, 2018

Agreed on the photos ( shame it's a perfectly serviceable relay though!) and dare I say it looking forward the the same high quality when Swann55 produces a 'How To' after he has removed his starter and swapped out the solenoid contacts 😀😀 only joking ( would be nice though) as I understand it to be a pita job and to capture on camera at the same time is a bit much.

paul m.

Swan55 · January 12, 2018

Gents,

Thank you all for your time on this issue, and for kindly looking up resources elsewhere. I will take it all on board.

As we are mobile thanks to another car, I can afford to take a little bit of time to do some more research, especially in case there are other maintenance tasks that can be carried out once we start stripping things down, and I've seen recommendations elsewhere for specific tools etc.

If I can take relevant pictures I will do so (and also look into how to post them at a more presentable size).

I purchased a new Battery charger yesterday from a well known German 'lower prices' superstore. It cost £13.99, feels sturdy, and has a 3 year warranty. I put it on this morning and my Battery was initially on only 1 of 4 bars - it is now charging nicely.

Will post back when I have some news - but that may not be for a while.

Have a good weekend,

Nigel

J4ck100 · January 11, 2021

Hi @Swan55

I have, this very moment, just had the very same experience as you had. The starter on my 1999 LS400 has been playing up as of late, often only providing a click instead of a full start.

Then for the first time, on this cold January evening, I started her up and to my disbelief I heard the starter keep cranking. I proceeded to remove the key from the ignition, however to my dismay, the starter motor continued to turn.

Luckily, I remembered that Lexus equipped these fine motors with a small tool kit in the trunk, so quick as a flash I grabbed a spanner and disconnected the Battery.

Now I am looking at replacing the Solenoids with the kit listed on eBay. Tell me, did that solve your issue? A mechanic said that a safer bet would be to buy a new starter motor entirely however I would rather save the pennies and help this green earth by repairing/refurbishing my existing unit instead, if possible.

Kindest regards,

jack