Hello. This is my first post here, although I have also posted it on a UK site.

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.

 

I'd check the starter relay first. It is located in the fuse/relay box behind the battery. When contacts pin #3 and #5 are stuck close, the starter continues to run.
If that relay is OK, the next step is to check the starter itself.

 

The days leading up to and including the run on condition all indicate relay/solenoid is sticking on (fusing the contacts). If this model has a solenoid on the starter, the relay contacts are bad and fusing together. In this case, replace the starter.

 

Those are good tests you did.
I'd say it pretty much isolates the problem to be with the starter solenoid, unfortunately. If the starter solenoid is stuck, current will flow directly from the battery, regardless of the starter relay and everything else, which is what you are seeing.

 

I had the same exact issue in an ES300, replaced starter, problem solved. Fortunately, it's a 10 minute job on an ES. It's really a shame that it's such a big job on an LS.

 

So it stops when you unplug or disconnect the battery, Right?

Now what happens when you go to reconnect the battery? Does it start wanting to crank again? If not then the contactor in the solenoid would not be fused or welded to the contacts. It could also be a bad ignition switch too.

 

Change the starter like others have suggested.

 

To everybody: many thanks for your time and advice.

To Dicer: You are correct. When I disconnect the battery, the starter stops cranking. When I reconnect the battery (with the ignition key removed) the starter starts cranking. If I then insert the ignition key and turn the ignition on, the engine fires up as normal - but the starter motor keeps on cranking (even with the engine running). I then turn the ignition key off and the engine stops but the starter is still cranking (until I disconnect the battery).

It is as if the starter motor is not disengaging. The starter is continuously 'live'.

By now, the car has been left standing still for a few weeks, so I would not be surprised if the battery has drained down a bit. Therefore to eliminate the question of low battery charge potentially adding to my confusion, I will today go and buy a battery charger, and make sure it is thoroughly topped up. I will then repeat my tests in a few days and post back my ongoing observations.

many thanks

 

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.

 

Oldskewel,

thanks for your consideration, and please excuse my mechanical ignorance.

If the starter solenoid is indeed stuck / welded, would we still expect the starter to crank ? would the starter just appear to be dead and make no sound or just a 'click' ?

(if I turn the ignition key on, then the engine actually starts - it's just that the starter motor does not stop cranking)

many thanks

 

Solenoids engage via electromagnetics. So when the Ignition has power, it engages. A bad solenoid can get stuck and fail to disengage. Therefore it will keep turning the starter gear

 

Good question. Answer is that yes, if the starter solenoid is somehow stuck in the ON position, then yes, it will be completing a circuit directly from the battery to the starter. So in this case, regardless of everything else in the car (relays, fuses, ignition switch, neutral safety switch, etc.) when the battery is connected, current will flow to the starter and the starter will crank.

The fact that it cranks suggests that the starter itself might be OK, but the solenoid is stuck. When you get in there, it may be wise to replace the starter as well as the solenoid, unless you can be really sure the starter is OK.

I have not confirmed this on the Lexus circuit diagram, but if you really want to rule everything else out, I think removing the 120A fusible link (not as simple as pulling a fuse, but does the same thing) shuts off everything else in the car except the connection to the starter. So if you remove that link and have the same problem, it is 100% guaranteed to be a problem with the starter solenoid.

The starter solenoid does two things when it is working properly: 1- it moves a gear to connect the starter motor output to the flywheel (with gear teeth) on the engine; and 2- closes a huge relay switch that connects the starter motor to the battery positive terminal.

This basic starter circuit architecture has been true for many decades on all cars.

So on your car, since the engine actually cranks, and since it does that when the battery is connected, I will guess that there is no click from the solenoid, since it already frozen in the ON position, with the gear engaged and the relay thrown to close the circuit.

 

Oldskewel,

thanks for the great explanation.

I will look into the 120A fusible link.

many thanks

 

[QUOTE=oldskewel;1008012
One thing that is a little more complicated on the Lexus is how when you turn the key to start, you can actually release it almost immediately and the car will keep cranking until the car starts.[/QUOTE]

This is NOT true , the starter does not continue cranking when the key is released. You simply have a fused solenoid; no need to pull the fusable link, just accept that the solenoid is bad. Solenoids and relays are exactly the same thing; one is designed for only a few amps of current, the other for hundreds of amps, that's all. The starter relay simply provides current to the solenoid's coil. The 98-2000 400s aren't quite as bad to fix as the earlier models, since there is no EGR plumbing.

 

Hope that helps. Look up instructions on removing the link. It is about 100x more difficult than it looks. Not really hard, but it looks really easy, which can be deceiving. Don't try to figure it out yourself, just find instructions and follow them. I'll see if I have any notes from when I did it on mine (replaced mine just because the clear plastic shell was cracked from age and heat).