I have a 1992 Lexus ls400. I'm stumped with this issue. I started it up in the morning and for the first couple seconds it was barely idling and maybe at about 200 rpm. After about a second and a half it jumped up and idled normally. I didn't think anything of it. Then a couple seconds later the car stalled and I went to start it again and nothing. No click or anything. Starter doesn't make a sound. I checked fuses, and the relays in the engine compartment. I couldn't find anything that was wrong. Does anybody know what this might be or what to look for? It was running and driving perfect before this happened

 

I'm assuming the battery is properly charging? What kind of voltage do you have? Any check engine light before it shut off?

Will it start if you put the car in neutral?

 

I tried it in neutral and still nothing. I've tried 2 different batteries that were fully charged so battery power isn't an issue

 

It could be a starter, ignition switch, neutral safety switch, etc. Do you have a multimeter?

Could you hear a click when you pushed the brake in before moving the selector out of park?

 

Yes, I hear the click when pushing in the brake. I highly doubt it's any of those because whatever caused this to happen made the car stall as well. If the starter went out it wouldn't have caused the car to stall. I cannot figure this out for the life of me

 

Get the battery tested or at least put a volt meter on it.

 

I've tried 3 different batteries that were fully charged and reading 12.6v

 

All the batteries you have were load tested? Are the terminals making a good connection? Don't go by how they look. What is the voltage when you're trying to crank the engine?

 

I have a few other celsiors, and they work just fine in them. I'm pretty sure they are fine lol. They were bought this year

 

My alternator caused the car to stall once it was finally bad enough. My neutral safety switch caused the car to stall once it was bad enough.

It's hard to diagnose without seeing the car. Can you pull any codes?

Has the ecu been rebuilt?

 

Ecu has not been rebuilt. I'm pretty sure it's not the ecu, I'm well aware of the leaking capacitor issues with them, but I've never heard of them causing a no crank condition. The car is a 92 so I cant check if theres any codes

 

It sounds like you're pretty familiar with troubleshooting, etc., so hopefully these comments help:

Not a big deal, but on the 200 RPM, are you sure the engine was actually going that slow, or could it have been just the tach showing that? I never take the tach as the truth ... well especially now that my tach is broken, LOL. But even before that ...

Sounds like you've got great confidence in the battery - good that you've removed that as a doubt. Easy stuff first.

A problem with the NSS could cause a start problem, but it "should" be out of the circuit regarding killing the engine. Good work on trying neutral.

There is a 7.5A "ST" (starter) fuse in the fuse box by the driver's feet. I once had an issue in my '91 where I got intermittent no-start (no clicks or anything at all), and then finally the intermittent became permanent. I eventually traced the problem to this single fuse, just before I was about to pull the NSS out. Usually fuses blow due to some electrical fault, but in this case, my fuse blew, I replaced it, and there were no other problems (and have not been for years now).

So I wonder if it could be that some temporary electrical fault somewhere caused the weird tach / engine RPM behaviour, and also blew your 7.5A fuse. So I'd check that fuse. Easy to do. I have not done it yet, but some advocate just replacing all the fuses in cars this old, and I may do that next time I'm stumped on a problem like this.

Here are a couple of posts with the starter circuit diagrams, one scanned from my 1991 manual (not sure if it's the same as your '92; hopefully same or close) and the other from a later LS400, not sure of the year.

https://www.clublexus.com/forums/ls-...l#post10564483

https://www.clublexus.com/forums/ls-...l#post10564445

Here's a post and thread with my description of the specific symptoms I had when I had my fuse problem.
https://www.clublexus.com/forums/ls-...ml#post9330608

Specifically, there it says, "when I turn the key from ON to START, the lights on the climate display go off, but other than that, nothing at all happens. No crank, no click, no hum, no change at all on the instrument panel" Looking at this now, knowing it was completely fixed by replacing that ST fuse, I'm still puzzled. But it shows how different systems on the car may not be as isolated as they should be.

Also in there discusses how I jumpered the starter relay, which is a good debugging step (if you can do that, you can rule out problems with the starter or battery), and also a practical way to get around until I found the actual problem and fixed it. LOL. Each time I needed to start the car, I would turn the key to ON, pop the hood, and momentarily put in the jumper wire to engage the starter, starting the engine.

I've given some ideas, but in general, I would trace through the circuit diagram, confirming voltages, etc. to see where things are working vs. not, and then isolate the failed component.

 

Thank you very much for that reply, I just jumped the starter relay and the starter spins very fast, which eliminates that problem, I was sure it wasn't the starter anyway. Also there is no fuel going through the lines. Maybe exu? Whatever made it die is not letting it crank from the ignition and not sending fuel pressure.

 

Yes, so check that 7.5A fuse next, and look at the circuit to see where the failure is.

Good that you've got the battery, cables, and starter all confirmed good now.

If you know you're not getting fuel, you might find this post useful, which I wrote while debugging a problem that ended up being a soft failing fuel pump.
https://www.clublexus.com/forums/ls-...ml#post9777959

That's from my '91, but be aware they made some changes from year to year in there, so you should check to see if your '92 is the same.

I remember distinctly while doing that trouble shooting, that if you somehow jumper the fuel pump to make it run independently of the engine running or during starting, you can *easily* hear the fuel flowing through the fuel rails in the engine bay. Easy to test.

 

I've checked that 7.5 amp fuse and it's fine but I replaced it anyway to be sure. It's not the fuel pump because when you jump the fuel pump it works. Like I said, whatever caused this is not letting it crank, or get fuel. I would assume it's not getting spark either. Something is not allowing it to be started which makes me think ecu, I was hoping someone might know what is going on